Troubleshooting 2 Stroke Ignition Problems

Author: Stuart Buckingham   Date Posted:30 March 2017 

The most common thing I get asked over the phone to assist with is diagnosing outboard ignition problems. Whilst I am always happy to try and help in diagnosis, it can be very hard to do so over the phone. Apart from having the right tools to assist in diagnosis, a basic understanding of how a two stroke ignition system works is fundamental. The following is a list of what makes up an ignition system from start to finish.

1. Battery

Your boat battery is where it all starts. Outboards require higher cold cranking amps than many other engines and therefore a dedicated marine battery with the correct cranking capacity for your outboard is a must. Without the correct voltage, your outboards starter motor may not be able to crank the flywheel fast enough to activate your ignition system.

2. Ignition Switch

To activate your engine and crank it over you need a switch. Every electric start outboard has an ignition switch and it will open and shut the starter solenoid. It also turns the engine off by shorting the CDI unit (power pack or switchbox) to ground. A faulty ignition switch can cause all sorts of problems with your ignition system and is more often than not overlooked.

3. Starter Solenoid

This is effectively a gate. The ignition switch sends a signal to the solenoid when you turn your key allowing it to open; this allows voltage from your battery to pass through it to the starter motor. If you're turning your key and the starter motor isn't cranking then you may have a faulty solenoid.

4. Flywheel

When your starter motor is turning over it is spinning your flywheel to create voltage for your ignition system and battery charging system. On the inside of the flywheel are magnets that spin around a stator at high speed to create AC voltage. The flywheel also spins around the trigger (or timer base) to determine your engines firing sequence or timing. Broken or loose magnets on your flywheel will cause ignition issues so they are definitely worth checking.

5. Stator

Your stator creates voltage for two reasons. To send voltage to your CDI unit (power pack or switchbox) to run your engine and to send voltage to your rectifier/regulator that will charge your battery. Engines with no spark or intermittent spark on one bank can be caused by a faulty stator.

6. Trigger

Nestled in with the stator under the flywheel is the trigger (or timer base). Probably the most overlooked part of the ignition system the trigger sends a signal to the CDI unit (power pack or switchbox) and tells it when to release voltage to the coil. A faulty trigger will result in no or intermittent spark and is often misdiagnosed as a fault with the power pack. Additionally, a faulty trigger shorting to ground will damage a power-pack so be careful if fitting a new power pack.

7. CDI Unit

Depending on your outboard brand these units will go by different names but, they will all have the same function and that is to store voltage from the stator and release it to your ignition coil when the trigger tells it to. Often a faulty CDI unit will see intermittent or no spark on cylinders and may only breakdown when your engine warms up.

8. Ignition Coil

Receiving voltage from the CDI unit the coil will amplify voltage and shoot it through to the spark plug. Faulty or damaged coils will have weak or no output. We see a lot of coil failures where customers are using a spark plug that is not recommended by the manufacturer.

9. Spark Plug

This is the last component in your ignition system. The spark plug receives voltage from your ignition coil and creates a small electrical spark within your engines combustion chamber igniting your engine's fuel and creating the explosion that drives the piston to spin the crankshaft and the flywheel where the ignition process begins over and over again. Spark plugs can foul up with oil and carbon on two stroke engines resulting in poor spark. They are by far the easiest part to check first.

10. Rectifier/Regulator

Fitting in somewhere between all this is your engines rectifier/regulator. It is always working and its job is to replace the voltage in your battery that you've lost due to engine cranking, using electric tilt and trim, running fish finders, lights or other accessories on your boat. It converts the AC voltage to DC voltage and regulates how much voltage it is putting into your battery. In a lot of cases, a rectifier/regulator also sends the signal to your RPM gauge (tacho) telling you what revs your engine is doing. Sometimes the first sign of a faulty rectifier/regulator is when your RPM gauge stops working and this is very common with older Evinrude/Johnson outboards.


There are variances here and there, but I’ve gone for the most common and basic approach on this occasion. I hope the above has given you some insight into how your outboard ignition system works. Keep these points in mind if you ever have a potential ignition problem and hopefully, it will make a diagnosis that bit easier.  But remember, in order to diagnose ignition problems properly a Digital Multimeter with a Direct Voltage Adaptor (DVA) is a must have tool for accurate diagnosis. Another very helpful piece of material is the CDI Electronics Troubleshooting Guide, click here for pages of helpful information on almost every two stroke engine.

To shop our range of ignition parts, click here.

Comments (109)

Mercury 2002 40hp 2st 2cyl

By: on 29 October 2019
Only firing on one cylinder. New plugs new coil( not genuine. After market) with 4 pin plug. If I switch coils the other cylinder starts running and the one with new coil stops firing. Could it be faulty new coil, or something else? Thanks

Outboard Spares Response
Hi, If the problem is following the new coil, then I'd guess the new coil is faulty. Cheers

1994 Mercury Tracker 90HP 2-stroke 3 cyl

By: on 28 October 2019
Great site Outboard Spares. Replaced the fuel filter & spark plugs on our 'new to us' Mercury 90hp 3 cyl a few months ago. After at least a dozen hours of operation we removed the plugs to fog the cylinders for winter and noticed that the top two plugs are somewhat blackened and clearly generating some sort of ignition in the cylinder, but the bottom plug is clean as a whistle - looks like the day I put it in. The motor seems to run reasonably well at low RPMs but does not put out as much power as I think it should at higher RPMs and sometimes seems to bog down like it is starved for fuel at higher RPMs. Any suggestion where I should start to diagnose this motor's issues?

Outboard Spares Response
Hi, Around that ERA they moved to a CDM Module assembly on each cylinder instead of a traditional coil. These were/are prone to failing as they age. If it is this type, you could swap the CDM Modules around (move the middle to the bottom and bottom to the middle) and see if you start getting spark on the bottom plug that you were not previously. If the spark does follow the middle CDM then you'll know you have a faulty CDM. The same can be done if you just have standard coils fitted. To me it sounds like this is the issue (coil breaking down under load) given the upper two plugs look like they are firing and the bottom appears like it's not. Good Luck.

2001 Tohatsu 25

By: on 26 October 2019
Hi. I have a starting issue, I’ve replaced solenoid put a new battery in, the starter motor engages but does not turn over. I’ve checked all lines and terminals for corrosion but they are clean. Pull start is fine thankfully but electric start won’t happen. Is it possible faulty ignition switch?

Outboard Spares Response
Hi, Thanks for your inquiry. I'd suggest carefully bypassing the solenoid with a set of jumper leads to the starter motor and see if the starter motor then turns over. If it does, you can assume the battery leads or the solenoid are no good. It could be the ignition switch, but unlikely. The ignition switch just sends 12 volts to the solenoid to open it. If the solenoid is opening for power to go through the solenoid and then the starter is actually trying to crank over, I'd say you have a problem with your leads or the starter motor itself. Good luck. Cheers

97 mercury 175 efi

By: on 24 October 2019
Motor starts no problem and has good spark and compression. Turn it on and it idles pretty good with a small miss but its had it for about a year. Recently though once I take it down the lake say 2 or 3 miles and shut it off it runs fine at high rpms. But once I fire it back up it has a harder time starting usually have to give it gas to start it and to keep it running it will sometimes take off fine but it loses 3 cylinders and just Boggs. But after a minute or so it will take back off firing on all the cylinders then it drops them again. I've went through and check and replaced alot of fuel related parts except got into the fuel injection. Could this be the switch boxes? I read in my manual that the fuel regulator could cause something like that to happen but even with the new regulator it's only running 35 psi when it should be up to 90psi. I'm lost

Outboard Spares Response
Hi, If the fuel pressure should be at 90 PSI then it's possible that the high pressure fuel pump in the VST (vapor separator) needs checking. Otherwise as far as ignition is concerned, yes it does sound awfully like a faulty switchbox or stator coil. I'd be leaning to faulty switch box though as in my experience these type are prone to failing as they get older. Good Luck! cheers.

90 Hp mercury 2 stroke 3 cylinder

By: on 17 October 2019
Motor overfuels and has this coffing sound in the water with no power and when motor idles only 2 of the 3 plugs make a difference but all three have spark but only 2 firing, could this be carburetor issues?? Thanks in advance

Outboard Spares Response
Hi, possibly a carburetor issue. I probably need a bit more information regarding the "no power" and "overfuelling", as in when is the engine overfuelling (RPM range) and when does the engine lack power (RPM Range or throttling onto the plane)? If your carburetors haven't been serviced for a while I'd start with them and then go from there. Cheers

Mercury 2004 50HP 2 stroke outboard

By: on 15 October 2019
had a couple of months of perfect running then last Saturday whilst heading back at the end of days fishing travelling at around 16 knots engine just died stopped dead. checked fuel ok tried re starting and it started but very weak and only ran for 5-10 seconds then cut out this kept going on for an hour or so - on some starts i was able to put it into gear but it would shut down immediately - finally gave up and had to get towed at home have tried and same deal its starts strong but will only idle for seconds and then dies any thought? many thanks in advance alf

Outboard Spares Response
Hi Alf, Hmmm, could be one of 2 things. 1) water/debris in fuel. It could be that you've got to the bottom of your tank (end of the days fishing) and sucked up some water/contaminants in the fuel. Water will always sink to the bottom of the tank as will contaminants. Your engine may just need the filters cleaned or replaced and the carburetors cleaned. 2) Ignition issue. Likely stator. From what you have described it sounds like a faulty stator (if it is not a fuel issue). You'll need a digital multimeter with a DVA adapter to check the stator output. Read between the white wire with green trace and green wire with white trace. With these wires disconnected from the rest of the ignition system you should have between 180 and 400 volts. If you then connect the wires to the rest of the ignition and the reading is lower, then you may have a bad CDM Coil module. Good Luck. Cheers

1994 Johnson 50hp oil injected

By: on 8 October 2019
Hi there, I just picked up a 94’ Lowe pontoon boat and I’m having some issues. When I bought it the owner took me out on the lake and everything was working fine. I took it out on the lake a month later and it started up with the help of a little throttle. After a few minutes at no wake speed it would die but would start back up and die at idle again. Finally got it running decent and it seemed as if it was running degraded on one cylinder. And then finally died and wouldn’t start at all. Took it home and checked it out. Both cylinders #1/#2 have 120 compression and were getting spark. I noticed the plugs were fouled which looked like it was running rich so I replaced the spark plugs and cleaned the carbs. Tried cranking again and nothing. I noticed that when I pulled the plugs and cranked it to clean it out it was blowing a lot of oil out of the bottom cylinder. I’ve read that the oil pump plug can come loose with the vro pumps if I’m not mistaken and leak oil into the bottom cylinder possibly causing this? Any help?

Outboard Spares Response
Hi, I'd say that while the engine has been sitting without use for over that month period the VRO has leeched oil into the bores. You may have to use a fair bit of cold start (neutral throttle lever) and fuel priming through your ignition switch to get it started if the engine is really oiled up. I'd say this is all it is. If it were me, i'd disconnect the oil injection side of the pump and just pre-mix the fuel and oil at 50:1. VRO pumps were typically unreliable and the best insurance was to just mix your own oil and fuel and be done with it. Good Luck

1990 Yamaha 90 2 stroke

By: on 7 October 2019
Hard starting. Breaks down around 1900 rpms. Runs fine on higher rpms. Seems to be bottom cylinder not firing properly. Changed coil and cleaned carbs. Compression is 120 on all 3 cylinders. I pulled the plug wire on top and middle cylinder at 1900 rpms and each stalled the motor. When I pulled bottom cylinder wire motor still run.

Outboard Spares Response
Hi, I would try a spark test with a spark tester and see if the bottom cylinder is definitely not firing. I would then swap the coil primary wires to the CDI Unit (change their positions, number 3 to number 1, number 2 to number 3 etc) and see if the problem stays on the bottom cylinder or follows the CDI Unit Output position on the CDI Unit. If it does follow the CDI Unit Output position, then you may have a faulty CDI unit, or a faulty Timer Base. To confirm if it is a faulty timer base, you will want to test the timer base wires connecting to the CDI unit. Ensure voltage is even across the 3 input wires. Good Luck. Cheers

1991 Evinrude 200hp

By: on 30 September 2019
I was driving it running about 45mph and the motor just shut off. It would start up then die now it has no spark. I disconnected the black and yellow wire from the power pack (the plug) then I turn the key and it fires right up and runs but under load it only goes 6mph like it’s limiting the amount of power. I replaced the ignition switch and still did the same thing when the black and yellow wire is disconnected from power pack the engine runs just can’t shut it off but when it plugged in there is no spark?? I just noticed the rectifier is burnt but I was told that would not keep it from running and the kill switch has continuity I also check the shift switch and it has continuity please HELP!!! I’m so fustrated...

Outboard Spares Response
Hi, I would disconnect the yellow wires from the rectifier and re-test the sytem. I'm confident from what you have said that this will be your problem. Cheers

92 johnson 115 with vro

By: on 27 September 2019
Motor starts fine and idles good. I take it to full throttle and it runs smooth for about 5 seconds and then it bogs down or lurches. I take throttle back to slow idle for 10 seconds go back to full throttle runs smooth for 5 seconds bogs down again.

Outboard Spares Response
Hi, Thanks for getting in touch. It is hard to say exactly what the problem may be. From what you've said about it bogging down after full throttle I'd be thinking it's not getting enough fuel at WOT. This could be because of the VRO system or perhaps a restriction in the fuel system somewhere. Alternatively it could be an ignition issue, possibly stator or pack but very hard to determine with the limited information at hand. Try the fuel system first and see how you go, in particular check there are no blockages in the tank breather lines. Good Luck.

1985 Johnson 50hp VRO

By: on 16 September 2019
Hi, Just got a second hand boat. The engine jumps beautifully and goes great. The only problem is it seems when I stop the engine gets flooded. Could this be due to the location of the red choke switch internally? I believe it was open entirely. I just don’t want to take out again until rectified as it would take about ten minutes of clearance time to get going again.

Outboard Spares Response
Hi, To my knowledge the red valve on the primer solenoid can cause flooding if left in the open position as it is effectively a choke. Cheers

1977 70hp No Spark When Cool

By: on 14 September 2019
With Fall arriving and cooler weather in northern Maine my 1977 3 cylinder Evinrude quite often does not get a spark on any cylinder sparkplug in the morning. I have tightened all the wires on the power pack. I have discovered on a sunny day if I take the hood off the engine and expose the powerpack to sunlight for an hour or so I do get spark to all cylinders and the engine runs fine at all speeds around the lake. I have also determined on a cool cloudy day when I don't get any spark that if I use a heat gun and focus the hot air on the power pack for about 15 seconds that all the plugs get spark and the engine runs normally out on the lake for extended periods. Thus far I have not been able to find any mention or resolution of this problem and am reluctant to purchase a new powerpack until I am reasonably certain it will resolve the problem.

Outboard Spares Response
Hi, I think you have figured out your problem. Faulty Power-pack. Everything you've done points to that being the problem. You could test the stator with a digital multimeter and DVA adaptor to see if the output of the stator is at least 150 to 400 Volts, but I honestly think what you have done is quite ingenious and I'd be certain a new power-pack will fix your issue. Cheers

30 hp 2 stroke yamaha outboard

By: on 12 September 2019
At initial start-up, everything runs fine. I can run the outboard for 2-3 hours with no loss of speed or power, but if I shut the motor down or if it runs out of gas, I will have to wait for 20-30 minutes before it will restart. Runs good on all cylinders. Any thoughts on what to check for?

Outboard Spares Response
Hmmm, interesting! Initially, I was thinking your engine was simply flooding but if it does the same thing when it runs out of gas then it may not be....however, is it an oil injected model?? If it is it could be that your engine is over oiling and this basically means your spark plugs may be fouled due to all the extra oil. Check the plastic "joint link" fitting that is on the end of the rod that runs between the oil pump and the carburetor (on the oil pump end). If this connector is cracked or damaged, it could be causing your oil pump to "default" to full advance which means your engine will constantly be running at it's maximum oil delivery. If that's the problem it's an $11 part and all fixed in 5 mins. Hoping this is the problem. Let us know how you go. Cheers

1989 90hp Johnson 2st V4. Missing when warms up

By: on 9 September 2019
Only when it warms up, either 45 min normal running or 20 min towing tubes. Engine starts missing. Replaced plugs and was a little better for a short time. Replaced coil packs (with a loan pack) and no change. Checked HT leads with meter and all good. Checked fuel breather not blocked. It is not limp mode (I don't think) as no alarm goes off. Runs ok at low revs then misses when cranked up

Outboard Spares Response
HI, When you say coil packs I assume you mean coils? I'd be checking the power-pack/s. Power-packs tend to start failing as the engine heats up when they are nearing the end of their life. Power-packs will also cause a miss. The other thing that will cause a miss is simply an engine that needs the mixture screws tuned on the carbs. However, if you suspect that it's more than a simple carburetor adjustment then I'd be looking at the aforementioned scenario of a faulty power-pack. Cheers

bass tracker won't start.

By: on 1 September 2019
Hi I installed a new switch on 97 force outboard. when I tried to start it turned over 4 or 5 times it was firing;then turned the switch nothing , I checked the starter it was engaged with the flywheel will not drop below the flywheel but both will turn by hand.

Outboard Spares Response
Hi, I'm assuming you are referring to an ignition switch. I'd be checking your battery voltage as it could be that you just have low battery voltage and this is causing the starter motor to not turn over fast enough. It could also be old battery leads. IF, the engine is now not cranking at all (even with a fully charged battery and good battery leads) then I'd check the way you've wired in the new switch. NOTE: It could also be a faulty starter solenoid OR tired starter motor, but I'd check the previously mentioned suggestions first. Cheers

1990 8 hp Johnson, no spark to top cylinder

By: on 31 August 2019
Hello, I have an 8 hp Johnson,circa 1990. Its only running on the bottom cylinder. I put an inline spark tester in place, and the top cylinder is not getting any spark. I have replaced the coil with another one from a parts engine and that didnt make a difference. I have swapped plug wires and that also didnt make a difference. I did order a new CDI that I put in place, but with the new CDI, i didnt get spark in either cylinder so im sending the CDI back, but just wondering if this could be anything other than a bad CDI?

Outboard Spares Response
Hi, Thanks for getting in touch. First I'd be disconnecting the stop switch (black wire with yellow trace) from the circuit and re-testing. It could be you have a faulty stop switch causing you grief. If this doesn't fix the problem then I'd consider the stator is potentially faulty. I'd be testing it's output using a digital multimeter with a DVA adaptor. I think you should be getting between 150 to 400 Volts between the brown and brown and yellow wires. Hopefully this helps. Cheers

1989 Yamaha 175 precision blend v6

By: on 27 August 2019
Port side bank (all 3) has no spark. Coil packs are good (swapped with starboard) and wires ohm out to terminals. The Yamaha Control Unit (icu-10) has odd ohm readings based on a generic manual. If the icu-10 is faulty, would it cause 3 cylinders on port side not to fire? Not sure where to check next. Any suggestions?

Outboard Spares Response
Hi, Ok I'd be swapping the stator wires over on the CDI Unit and conducting another test. From memory you'll be swapping the blue and red wires over from their positions on the CDI Unit. These wires are what fire the port or starboard bank. If you find that the problem now shifts to the starboard bank, you most likely have a faulty stator. Also, check the engine is not over-heating and causing the CDI unit to limit RPM. You can disconnect the temperature sender wire and see if this helps. You could also disconnect the stop wire (white wire) from the CDI Unit and see if this makes a difference also. My gut feeling is that your stator is faulty, I may be wrong.... Cheers

98model 25 nissan c3

By: on 25 August 2019
Ok I bought this motor knowing it had a problem . Problem is when trying to start its backfiring and when and if it does start its still popping and backfiring will only run for a short min before it stalls and sounds really weak

Outboard Spares Response
Hi, Ok, so I'd think timing is the issue, or some kind of fault in the ignition. Is the engine running a rectifier? If so I'd disconnect it and see if the problem goes away. Secondly, disconnect the stop wire from the kill switch/stop switch. See if the problem goes away. Third, could be a faulty coil OR CDI unit. I actually don't have any testing procedures for these components. If you can get your hands on a second hand CDI, or coil it may be worth while. Cheers

1985 90hp yamaha

By: on 22 August 2019
Starts and idles just fine. Put the boat in gear and start to go revs up to around 2000 rpm then shakes and misses pull back to idle runs fine. Idle it in gear for 10 to 15 minutes shut it off 10 minutes runs fine the rest of the day. Clean carbs couple of times put new fuel pump on oil gauge works grounded temp senser alarm go's off help

Outboard Spares Response
Hi, sounds like it could be fuel or ignition timing. If after cleaning the carbs it is still having the same problem then I'd think potential ignition problem. Try disconnecting the stator wires that run to the rectifier and re-test. If the problem disappears your rectifier needs replacing. Otherwise, check all linkages between the carburetors, throttle and timer base. These engines have plastic joint link fittings that sometimes crack and cause linkages to slip, which may be causing the timing not to advance when it should. Try these things and see how you go. Cheers

81 70 horse evinrude can't get over 3,000

20 August 2019
I've changed coils plugs rectifier checked timming carbs all question is go and use trim with moter running at 3g voltage will drop to 12 an slowly creep back to 12.5 when I could get it to 4500 rpms voltage would jump 13.5 is it possible for ignition running off battery and charging coils keeping battery up just enough?

Outboard Spares Response
Hi, to answer your question, I don't think so. You could try changing over the battery and seeing if this fixes anything but I'd say it's unlikely. I'd be now looking at the following. 1) Check all linkages between the throttle, carburetor and timer base. Make sure that all linkages are activating as they should and that none of the plastic end fittings on the small control rods are cracked or broken. 2) Check if the temperature sender in the cylinder head connects to the power-pack. If it does, disconnect it and see if the engine now runs properly. If it does, your engine either has an overheating issue (faulty thermostat, waterpump, blocked head, etc) OR a faulty temp sender. 3) Check stator output. Ensure stator voltage output is between 150 and 400 Volts. You will need a DVA meter for this. See how you go with this. Cheers

1989-1991 evinrude 175hp 2 stroke VRO no spark on

By: on 19 August 2019
hi, tested coils, leads and plugs on other known working cylinders without fault to any of those parts. looking for accurate diagnostic steps/specs to move forward. the CDI is a sealed unit. any accurate info on testing the cdi, stator and trigger would be greatly appreciated. thankyou

Outboard Spares Response
HI, More information would be great. What is your engine doing or not doing? Cheers

1981 evinrude E70ELCIH

By: on 19 August 2019
I have put new plugs coils rectifier clean carbs I can't get to go past 3000 RPMs check timing 15 degrees top dead center adenoidal idling around 1100 RPMs put in gear wide open throttle 2000 RPMs I use trim voltage drops to 12 slowly creeps up to 12.5 and we'll stay there when I did get it to go over 3000 I would hate about 45,000 RPMs voltage would be 13 / 13.5 by me not getting over 3000 RPM would that be caused by a faulty stator would the ignition system be running off the battery and charging system is enough to keep the battery charged is that possible

Outboard Spares Response
Hi, Thanks for getting in touch. A couple of things spring to mind. Check the nozzle gasket on the carburetor is fitted. I have had these in the past where it's been left off during the service of the carburetor and subsequently won't let the engine perform. Also, try priming the primer fuel bulb on the fuel line while trying to get above the 3000 RPM to see if that makes a difference, Could be the fuel pump has the problem. Have you changed propellers? If you've fitted a propeller that is too large (in pitch and diameter) then the engine may be having trouble spinning that size propeller on your vessel size and weight. Lastly, have you checked spark? I know you have changed the plugs, coils and rectifier, but are you getting spark on all 3 cylinders? Feel free to shoot me an email if none of the above gets you out of strife. Cheers

2012 50hp 2 stroke

By: on 18 August 2019
Gday, Please help..... Went to take the family out for a run in our peace of joy. Started beautifully using choke for cold start off the trailer to the pontoon, turned her off to park the car. Started ok with family aboard, motor run out as soon as left the pontoon and not able to re-start. At first when turn the key engine would try kicking but nothing, very quickly it sounded like dead battery. Got boat home and checked battery, battery 12.54 and good. Tried starting at home, when turned the key and watching starter move up to turn fly wheel slightly then stop, appears to be electrical/ignition issue...... any ideas or suggestions please?

Outboard Spares Response
Hi, Sounds like battery to me. 12.54 resting isn't that great. I'd be putting the battery on a charge and then trying again. If the engine then fires up ok, It may be your battery is on the way out and needs replacing, especially if it is not holding charge. See how you go. Cheers

79 johnson V4 85hp Constant miss through rpm

By: on 18 August 2019
I have a 85hp V4 that keeps a constant miss through all RPMs and idle. Worrying in time it can damage my lower unit. Have changed and gapped plugs but is hard to figure out where it's coming from.

Outboard Spares Response
Hi, It could be a few things. Try disconnecting the yellow stator wires that connect to the rectifier and test engine. A faulty rectifier will cause a miss across most of the RPM range. A cracked or broken flywheel magnet could cause a miss through the RPM range, as could a faulty ignition coil. On the other hand, it may not be ignition. If the engine is sucking in air or the carburetor mixture screws are not set properly then this could also cause a miss. Try the ignition first as I've suggested. Otherwise, maybe give the carbies a service and tune. Cheers

1998 50hp johnson outboard won't fire?

By: on 16 August 2019
we have a 1998 50hp johnson that wont fire. We were out in lake running normal and it made a funny rough noise and quit running. It had to be towed. We replaced the power pack, coil and new plugs. Still won't fire. What's next??? We are not boat mechanics but tit didn't seem hard!

Outboard Spares Response
Hi, Thanks for getting in touch. If the engine is turning over (not seized) and now won't start and there was a "funny rough noise" then I would be removing the flywheel and checking for a damaged magnet. If you have a damaged flywheel magnet this would explain the rough noise and subsequent issue with the engine not firing. Also, check your stator is not damaged as a broken magnet from the flywheel may have caused damaged to your stator. Try this and see how you go! Cheers

2000 35 johnson ooutboard

By: on 10 August 2019
kicks over & runs good .but every now & then just cranks over & wont start .then will start after a few goes.flushed motor other day ,stopped it & tried to start straight away & took a few goes to kick over then runs happydays?

Outboard Spares Response
HI, I'm assuming this is a 3 cylinder model. These engines had a number of issues with the powerpacks. I'd first start by disconnecting the stop wire from the powerpack plug (Black wire with yellow trace). Once disconnected check to see if the engine experiences the same problems. Remember, you won't be able to stop the engine with the key switch unless you re-connect the wire. If the problem is now resolved then the ignition switch or harness has a problem. I'm just guessing that it is a spark issue, there is a chance it could also be fuel related but on the surface it sounds like a faulty power-pack. Cheers

2002 yamaha 90hp top cylinder stalls and dies afte

By: on 9 August 2019
hello. hope you can help me. I have a 90hp yamaha 2 stroke. All 3 cylinders have 115 compression, spark plugs good, and carbs rebuilt, cleaned and getting fuel. all 3 cylinders seem to get sparks but the top one can not run by itself whereas 2nd and 3rd cylinders run strong alone. Top cylinder stalls and dies after few seconds. In the water RPM doesn't past 4000 on WOT. I believe the top cylinder is preventing the RPM from going higher. Been dealing with this for months and my mechanic scratching his head. :T Thanks in advance.

Outboard Spares Response
Hi, So a couple of suggestions. Have you tried switching coils around to see if the problem follows a faulty coil? Have you tried swapping propellers to see if it is a propeller issue, E.G: trying to spin a 21 pitch when should be a 17 pitch..... Also, check all linkages to ensure that there are no cracked plastic linkage ends that are preventing the throttle and/or timing from achieving full movement. Maybe also try priming the primer bulb while underway to see if this changes things. You could have a faulty fuel pump, although I'm not convinced this is the case but worth trying. The other thing is that these engines run a CDI Unit with an advance lever. This adjusts timing as the throttle increases. I would be checking this as it could be the source of your issue, presuming that the problem has just appeared out of nowhere and not straight after works done on the engine. It is not un-common for this lever to "wear" and cause ignition problems. I'd check the linkage going to this advance lever for cracks in case it is a simple cracked fitting causing dramas. I hope this helps point you in the right direction. Cheers

40hp tohatsu 2stroke no power under load

By: on 31 July 2019
Was full noise in the creek then suddenly lost power and runs at 10kmh full throttle any ideas of what my issue could be

Outboard Spares Response
Hi, Is the engine RPM still high but you have little speed? (potential slipping propeller bush) Or is the engine not achieving high RPM anymore? (Potential rectifier, stator or fuel issue) If you can supply some more details we'll do our best to assist. Cheers

why my johnson 1994 150 2 stroke fast strike shut

By: on 31 July 2019
run good till it warms up than just shuts down

Outboard Spares Response
Hi, Thanks for getting in touch. Have you checked for spark when the failure occurs? Meaning, have you tried with a spark tester? Also, is the engine achieving full RPM or are you warming it up at idle and then it's stalling when you increase RPM? Try and get back to us with a few more details and we'll do our best to help. Cheers

1997 Evinrude E115ELEUC misses at WOT

By: on 31 July 2019
Hi, i’m chasing a problem or multiple problems with maybe you could help. Bought this motor two years ago. Starts fine, idle fine but won’t go over 3900 revs. If I push the trottle over that point it begins to miss and it get worst if push it all the way. I was thinking of gaz problem do I cleaned the carbs no change, I found that the diaphram was cracked so I rebuilded the fuel pump, no change I bypassed the oil pump and mixed my gaz cause it was smoking a lot too no change. Change the plugs. Then I removed the plug wires one by one and on one cylinder the fire was poor and intermittent so I switched the coils and the problem stayed on the same cylinder so I changed the power pack and no change. Before changing the power pack I checked the compression it is 115-118-118-120. Since I changed the power pack there is a vibration like the motor is running on three cylinders. Any ideas ?

Outboard Spares Response
Hi, So it could be a whole bunch of things. My first question is, what is your propeller pitch? Is it as simple as having a prop that is too big and won't allow the engine to reach its appropriate RPM? Second, try disconnecting the stop circuit from the power-pack. It is the black wire with the yellow stripe. If the engine now runs well you either have a problem with the stop-switch, shift switch or harness. Third, try changing the spark plug leads around. I know you switched the coils, but try the leads, it could be a lead shorting to ground. Let us know how you go with the above. Cheers

Yamaha 20A 2 stroke

By: on 29 July 2019
Having a struggle with this one. It will start and run well. Ticking over with no problem. It revs well and doesn't miss. After about 10mins, the engine just dies. Trying to catch it by giving it a bit of throttle or by giving it a bit of choke has not effect. Once it stops, it won't re-start for about 45 mins. It starts with no throttle or choke. Any ideas?

Outboard Spares Response
Hi, ok so, first things first. Check that the engine isn't overheating. Assuming it is pumping plenty of water, I would pull the thermostat out and check it is operational. Just place it in a mug and pour some boiling water on it and make sure it opens. Next, assuming the thermostat is working correctly, I'd be running the engine as you normally would preferably close enough to shore that you can easily get back to land, to then conduct a spark test (or just back your boat down at the ramp on a quiet day and run it on the trailer). Preferably, you want to have a spark tester as this is the safest way to check the engine does or does not have spark. If you find the engine does have spark after it stops, I'd be looking towards a fuel issue. Possibly as simple as blocked breather on the fuel tank or faulty primer bulb, or even a worn fuel pump. If the engine doesn't have spark, I'd be looking at the CDI unit. Faulty CDI Units will give grief when the temperature around them increases and the unit gets hot. This could also be the issue. Hopefully one of the suggestions is enough to point you in the right direction to solving this problem. Cheers

96 Johnson will not idle

By: on 28 July 2019
My son and I have been working on his 70 Johnson and are baffled on how to fix it. We have checked compression and spark, cleaned the carburetors,and everything we can think of. We used the OMC YouTube video to try to get it to idle, but we cannot get it to idle with the butterflies closed. If we hold them open a little and prime it we can get it to run, but we can hear a cylinder drop and pick up again. I’d say we have watched countless videos without any success. At one point we swapped carburetors and moved the miss to the other cylinder. We had another carb but it didn’t change anything. Any advice you can offer would be gratefully appreciated.

Outboard Spares Response
Hi, Thanks for getting in touch. The idle speed/adjustment is done on this model via the timer base adjustment screw. There are a few steps involved in setting this all up and I'm not sure whether you have followed these steps for this model without success OR whether you have but have an underlying ignition problem. This model did have problems with the timer base and power-pack. It could be that you have an issue with one of these, or even a coil. Depending on where you are based, perhaps send us an email and we can point you to a company that is highly experience in this ERA and Model of engine and may be able to check if you've set up the linkages correctly, and/or diagnose your ignition problem, should there be one. Cheers

Yamaha 115 2 stroke outboard

By: on 27 July 2019
Fires right up. Runs great for about a hour and shuts completely down. Doesn’t bog or anything it just shuts right down. Checked for spark out in the water and no spark. Wait a hour and it fires right back up. Runs for a while than does the same thing , after a few days it’s got worse and had to eventually get towed in. Next morning went to boat and fired right up in drive way. I don’t want to take it back out until I figure out this intermittent issue.

Outboard Spares Response
Hi, So If it is total loss of spark I'd suggest it's probably the stator or the CDI Unit. Early "screw in" CDI units were prone to failing, but the later model CDI units were pretty good and it was the stators that proved to be the weak link in an otherwise reliable ignition system. First of all, if its a "screw in" type CDI Unit then try disconnecting the white (stop/kill) wire to the CDI Unit. If the engine then runs trouble free it's likely to be a stop circuit issue. If this doesn't fix the problem, then I'd be checking the stator output. You'll need a Digital multimeter with a DVA adapter. Between the brown stator wire and the red stator wire you should have 85 volts minimum. Between the blue stator wire and the black/red stator wire you should have 16 volts minimum. If these are not within spec the stator has a fault. If the stator is within spec, I'd then be looking towards the CDI Unit as the faulty component. Hopefully this points you in the right direction. Cheers

No response on number 2 cylinder

By: on 18 July 2019
Hi I have a 1994 yamaha p60 TLHS outboard. When I pull the plug wire off number 1 cylinder it will fall on it's face. And when I pull wire off number 3 cylinder it also will fall on it's face but when I pull number 2 plug wire there is no response. I have changed coils no better replaced the reeds no help replaced fuel pump no better. Compression on number 2 is about 15 pounds lower then the other two don't know if that is the problem or not. Looking for some more input. Thanks Mike

Outboard Spares Response
Hi Mike, Thanks for getting in touch. Are you chasing a running problem with the engine? If the middle cylinder is 15 pounds lower than the other 2, then I would pull the head off and inspect the bores, provided it is a running problem you are trying to solve. It'll only cost you some time and a head gasket. Head gaskets need to be changed periodically (say every 4 years), so it won't be a complete waste of time if you don't find anything wrong with the bores, rings, etc. Good Luck. Cheers

Mercury 175 V6 1992 2 stroke

By: on 16 July 2019
Hi, is t true these engines will drop down to 4 cylinders under 1800 rpm similar to the 4 cylinder 100/115? I have had conflicting information. Many thanks.

Outboard Spares Response
Hi, I have never heard of this on the V6. The way the ignition system works I would doubt it. Given it is one switch box per bank of 3, I fail to see how this basic ignition system would cut out only 2 cylinders and not 3. I'm happy to be proven wrong or corrected but to my knowledge they always ran on six cylinders. Cheers

1996 mariner 90hp 2stroke

By: on 15 July 2019
i have a 1996 mariner 90hp 2stroke it has just been rebuilt idles fine in gear soon as i go to full throttle it misses and farts around at 3000revs does rev past 3000revs but hates it

Outboard Spares Response
Hi, So your ignition system on this engine should be a single switch box, stator, trigger, rectifier and 3 ignition coils. I would first disconnect the yellow stator wires from the rectifier and retest. If the engine now runs well, replace the rectifier. Ok, step 2, if this doesn't fix the problem connect a DVA meter between the stators blue wire and an engine ground (earth). Run the engine until you get to the RPM (in this case 3000 RPM) where the fault is occurring. Voltage should increase as the RPM increases. If the DVA Meter shows a sudden drop in Voltage just before the problem occurs then it's likely you have a faulty stator. Another simple check is to remove the flywheel and inspect the magnets for any that are broken or cracked. This could also be a cause of the issue. If none of this fixes your problem, get back to us. Good Luck.

Timer Base replacement.

By: on 10 July 2019
After a lenghty process of elimination and with the use of a DVA, my problem with "No Spark" on 2001 Johnson 60hp 3cyl 2stroke was a faulty Timer Base AND Power Pack as you mentioned was common. I have now installed both, and motor is now running good. My question i need to adjust/set Timing for idling on this particular outboard. Carbys and linkages and timing were all set by an outboard tech previously..........but now that i have replaced the Timer i need to check and adjust again? If so, is it just a matter of resetting the timing via the adjustment screw on the Timer Base until i get the 4degATDC according to the manual? Appreciate your assistance. Thanks.

Outboard Spares Response
Good Day, Well it is nice to hear that I was able to assist in some way and point you in the right direction. As for the timing, if it was set previously by a technician then theoretically you should be fine to leave it. If in doubt though, get the timing light out and go for it! Cheers

Intermittent Spark

By: on 10 July 2019
I have a 1988 40 HP Mariner/Yamaha 2 stroke. Motor starts great and idles just fine. However when rpms are increased and after boat planes out motor intermittently looses power. It will run great for a short while, maybe a minute or so then it will idle down. This particular motor only has one coil that feeds two cylinders. Top plug is wet after this happens. The carbs have been rebuilt and the plugs have been changed but I still have the same problem. I think it's electrical in nature. Any advice would be greatly appreciated. Thanks

Outboard Spares Response
Hi, Hmmm. Ok. Yes it could be a faulty coil or a faulty CDI Unit. Does the engine stall after it idles down? Feel free to send us an email if you like, Cheers

1978 mercury 1150 inline 6

By: on 9 July 2019
Sometimes I have spark sometimes I don't have spark when it sparks motor will fire right up and run for a few mins then shut off and wont start again for a few mins

Outboard Spares Response
Hi, So if your engine is running the twin switch-boxes then it could be that you have a faulty switch-box. These are very common to failing and easy to replace. Each switch-box controls 3 cylinders (or coils). You can trace the coil wires from the switch box to the coils to see which switch-box controls which three cylinders. Now, before you go buying new switch-boxes, the other problem could be a faulty stator. So to work out what is actually faulty complete the following. Swap the red with red/white and the blue with the blue/white wires connected to the switch boxes and see if the spark problem shifts from one switch box (group of 3 cylinders) to the other. If the problem does shift then you will have a faulty stator. If the problem does not shift then you'll likely have a faulty switch-box. It is normally recommended to replace both switch-boxes along with the stator if you have a faulty stator, although I understand that this is not always in everyone's capacity due to the cost. Good Luck!

1983 Evinrude 75

By: on 8 July 2019
Hi, thanks for your previous reply. We ended up changing stator and it fired right up. Now we have moved on to another issue. We took it to the lake a few days ago for a test run. Cranked fine, as soon as we would try and put it in to gear it would die Everytime. Husband brought it home checked carbs and cleaned again also checked for fire on all 3 plugs. He could take spark plug wires off top and bottom plug and no change in motor, when he took the middle one off it dies. All the plugs are getting spark but we can't figure out why it's only running on one cylinder? Could timing need to be adjusted? We have replaced coils, powerpack, rectifier and stator.

Outboard Spares Response
Hi, Yes I think it would be the timing that needs to be adjusted. But, I've included a few other dot points below of what it could potentially be. * Idle speed set too low and may need to be increased a couple of hundred RPM. * Disconnect stop wire from the powerpack and re-test. If this resolves the issue, check neutral switch in control box * Check linkages to timer-base (trigger) for any damaged parts. It's a possibility that your timing isn't advancing correctly as you start applying throttle. *Check timer base/trigger for a short to ground. *Check the correct power-pack has been fitted. They normally have a part number on them. *Check correct spark plugs have been fitted *Complete compression test. Check that you have good compression over 100 PSI on each cylinder within 10% of each other. Now, there is a possibility (and I say "possibility" as you can't rule what I am about to say out) that you have a worn block. So what can happen with these older Evinrude and Mercury engines (the mercury inline 6 motors were notorious for this as they got old) is that the block got worn around where the crankshaft sits inside the engine. This then allowed exhaust gases to move between cylinders thus stalling the engine. It would always happen when lower unit (exhaust) was under-water (not on ear muffs) and when the engine was put into gear. I have seen only a couple of these 3 cylinder engines with this problem, but it DOES happen. To my knowledge, there is no easy fix, if there is a fix at all. So, first and foremost go through the above checklist. Then I'd suggest before all hope is lost get a technician to check it for you as I have possibly left some things out that a technician with the engine in front of him will check. If you still can't resolve the stalling issue then perhaps it is the more sinister option i've suggested but I hope for your sake it's not. Good Luck. Cheers

79 mercury outboard 80 hp

By: on 5 July 2019
OK the motor stars easy and go's in and out of gear easy it also runs at high speed well , the problem Is only at idle ,it will idle for a min or two then start to pop and sputter and shut off . But upon restarting again it will start fine and idle fine again for a min or two and it will happen again? My question is could it be the flywheel key not being straight or aligned?

Outboard Spares Response
Hi, thanks for getting in touch. Hmmm, I doubt it is the flywheel. Your engine wouldn't idle hardly at all if the flywheel was off spec and you'd soon destroy the engine running at high speed if the timing was out. My guess will be the carby's and the engine is simply over-fueling (flooding) at idle. It was pretty common with these models and the inline 6 models too. You may need to run some carby kits through your carburetors and adjust them as necessary. I may be wrong, but this sounds pretty straight forward to me. Also just check what spark plugs are fitted to it. If your engine is a 1979 model, it should be running NGK BUHW-2 spark plugs. I hope this helps. Cheers

1983 Evinrude 75

By: on 4 July 2019
Hi, we have a 1983 Evinrude 75 that will try and crank but no fire. We have replaced all coils, rectifier and powerpack. After replacing this parts it fired twice. 2 days later it will not fire at all.

Outboard Spares Response
Good Day, Firstly, check you do not have a fault with the ignition switch. A faulty ignition switch will cause all sorts of dramas. Disconnect the black wire with the yellow trace from the power-pack and re-test. If this fixes the problem you have a faulty ignition switch, harness or shift switch. If this does not fix the problem then I would check the stator and trigger. Check the trigger for a short to ground. A faulty trigger can potentially destroy a powerpack. Next check the stator output, you'll need a digital multimeter with a DVA adaptor. You should be getting about 150V to 400V between the brown and brown/yellow wires. There are plenty of other tests you can conduct, but if none of the above present an outcome I would take your engine to a qualified "old school" technician that knows these older engines well. Good Luck!

1976 2 stroke Johnson 55 hp Outboard motor

By: on 4 July 2019
What wire off of the rectifier is the positive wire suppose to be connected to for charging the cranking battery when the rectifier has only three connections plus the grounding of the metal body base to the block?

Outboard Spares Response
Good Day, Typically it is the red wire that is the charging wire and the yellow wires go to the stator wires.

Tohatsu m90a

By: on 25 June 2019
Hello and thanks for the response... I have big problems with my TOHATSU M90A so motor has really slow acceleration and top speed... Carburetors are clean, I checked fuel lines, changed coils, checked termo senzor and oil sensor, there is spark, compression is ok... Symptoms: running on one or two cylinders of three ( when I unplug bottom coil engine dies, when I unplug middle one I can hear a difference but when I unplug the top one there is no difference in sound at all) problems begin to happen after hitting big wave last year.

Outboard Spares Response
Hi, I must admit I had to concur with an associate on this one but we were of the same opinion. There is a possibility your crankshaft has slipped. These engines like many Yamaha and older Suzuki 2 stroke outboards run a "pressed" crankshaft. This means that you can't physically remove the connecting rods as the rods are pressed into the crankshaft. We have seen it on Yamaha before when someone has been underway in their vessel and come to a complete or fairly sudden stop while travelling at reasonable RPM (lets say over 4000 rpm). Basically the flywheel keeps spinning even though the bottom end has all but stopped and this twists the crankshaft out of spec. Then the resulting issues are that timing is out of spec which would explain your problems. It might be best to take the engine to a technician and get them to check this for you. Sorry I can't give you a solid answer but I think this will be your problem given what you've already changed and the work completed. Cheers

J90SLEOC 1995 Johnson 90 No spark

By: on 24 June 2019
Was out all day running the boat and no issues. Coming in the motor died on me. After a couple minutes and numerous cranks, the motor started and we putted along for 400-500 yards and then died again. Once again, after a couple more minutes of numerous cranks, the motor started and we putted along for another 400-500 yards and then died for the 3rd time. After that the motor wouldn’t start. Got towed back and started running tests and found out there’s no spark. Replaced the power pack and still no spark.

Outboard Spares Response
Hi, ok so these ignition systems run an optical sensor which is basically a timer base. When we were handling the CDI product range we used to sell the optical sensor and powerpack as a kit. I would suggest that you probably need the optical sensor. Sometimes, you will need to use small washers to adjust the height of the optical sensor to ensure it reads correctly. Now, if this doesn't resolve your issue, then the next thing is the stator. These can be problematic but optical sensors and powerpacks were the main weaknesses in this ignition system. Cheers

Really strange phenomenon

By: on 21 June 2019
Hi. Im out of ideas now. I have a Johnson 90hp v4 year 89. New cdi box, ignition coils, wires and plugs. First it runs on three cylinders. Cylinder number 3 did not get spark. I mesured ohms and with dva. All seems Good from cdi. Still No spark, swaped ignition coil with cylinder number One. No spark on cylinder number One, problem folows. Put a new ignition coil and think problem solved. So wrong... I started upp, sounds Good. Runs on all 4. Put the Gear in and.. runs on three again. Give full throttle, when passed 1500 rpm the fourth spark plug starts to give spark. Runs great över 1500 rpm. Slowed down and when i came under 1500 rpms it losts One cylinder again. Revs upp again an runs on Four. On Idle it try to start the fourth spark sometimes. One second om three and another second on all four. Please help me

Outboard Spares Response
OK, so I'd be checking the trigger which is located under the flywheel next to the stator. Often the trigger fails on these units. The trigger basically tells the powerpack when to release the spark to the coils. If the trigger plays up then spark will be varied across the cylinders. Now, FYI, a faulty trigger shorting to ground can destroy a perfectly good powerpack. It is for this reason we normally suggest replacing the trigger before the powerpack. Basically, you could fit a new powerpack and the old trigger could ruin it within minutes. The other component to check would be the stator. You'll need a Digital Multimeter with a DVA adavpter to check the output and ohms. Now, before I finish. before you try any of this. Disconnect the stop wire (black with yellow trace) from the powerpack/s and test for spark. You could possibly have a faulty stop switch that is causing the grief. If this doesn't resolve anything, then check the trigger and stator as advised. Cheers

1995 Mercury 75HP 3 cylinder

By: on 18 June 2019
Motor was hard to start before fishing tournament. Finally got started and made a 15 minute run when engine just slowed down. RPMs never changed and had a very lite miss while running slow. I never let off of throttle when going 5mph but engine clicked in and ran full speed for a few minutes and then would click back out. That only happened 3 times in approx 2 hours. Performed OHMs test on stator and numbers came back 980 (spec calls for 800 -1100). Performed OHMs test on trigger assembly and came back 250 on 3 wires and 884 on purple wire (wires within trigger assembly - spec sheet calls for (800-1100). Have spark on all cylinders. The wires on trigger assembly are very soft feeling.

Outboard Spares Response
Hi, Thanks for sending that through. This is strange as you have said there is no drop in RPM. The only thing that I can think of (perhaps I'm missing something) that would possibly do this is a slipping propeller or something slipping in the lower unit. Generally if you get a loss of spark on these models, you will see an RPM drop as the cylinder or cylinders cut out. I hope this helps and sorry I can't give you anything more definitive. Cheers

Yamaha 85hp miss

By: on 18 June 2019
Bula sir,I'm having problems with this engine 85hp during starting all cylinder seems to be firing but tata full throttle the cylinder only fires with one no.3 and 1 and missing wat could be the fault?

Outboard Spares Response
Bula! It could be an ignition coil breaking down at higher RPM or possibly the CDI Unit, Stator or Timer base. Very hard to know from what you have described as there is limited information. I would start with the coil. Switch the coil positions to different cylinders and see if the fault shifts to another cylinder. If it does replace the faulty coil. If not, check the wiring going into the CDI Unit and then from the CDI Unit to the coil. Make sure all contacts are clean and free of rust or corrosion. Make sure there are no bad earths in the sequence. To test stator output at WOT you'll need a Digital multimeter with a DVA adaptor to check the output and resistance of the stator. Not everyone has access to this equipment so possibly taking it to your local technician is the next step but given you sound like you're in Fiji that may be tricky. Good Luck.

2 stroke Mercury inconsistent about cranking

By: on 18 June 2019
2 stroke 50 hp Mercury outboard runs well, cranks a few times, then won't crank. I remove plugs, turns engine over, replace with clean dry plugs and it runs well again for a while. But it's just a matter of time before it won't crank and I'll have to repeat the cycle.

Outboard Spares Response
Hi, It could be a few things. I would suggest checking the battery leads and ensuring they are not stiff and suffering from any internal corrosion which can reduce the voltage going to the starter motor. The second thing would be to check the starter motor itself. If it is quite old then maybe it needs a new brush-plate assembly or just brushes. I hope this helps. Cheers

1988 Mercury 2 stroke 4 cyl no spark on the bottom

By: on 16 June 2019
Have a 2 stroke motor that runs and has a bad miss. Put top off check it out top 2 cyl. Have good spark the bottom has no spark at all. Any ideas

Outboard Spares Response
Hi, If the bottom cylinder is not firing then it could be a couple of things. Firstly try a new spark plug. It could be something as simple as this. If not please read on. 1) Faulty Coil. Try switching the coils over and seeing if the problem follows the bottom coil that's not firing. If it does replace the faulty coil. 2) Faulty switch box or timer base. Check the voltage coming out of the switch box to each coil (measuring from the switch box, not the coil). If the voltage is low for the bottom coil (compared to the others) then check the voltage going into the switch box from the timer base wires. If the voltage from the timer base wires going into the switch box is the same across the 4 wires then it is likely the switch box that has a fault. If the voltage going into the switch box from the timer base is low on the bottom cylinder wire then the timer base likely has a fault. NOTE: If you have a faulty timer base then this can cause damage to the switch box. It is often a good idea to replace both at the same time, or if unsure of the fault, replace the timer base first then you won't risk damaging a new switch box. I hope this helps. Cheers

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