How To Store Fuel In Your Boat

Author: Stuart Buckingham   Date Posted:7 March 2019 

Blog - How To Store Fuel In Your Boat

You’re heading home from the boat ramp, it’s been your last outing for the season and soon the boat will be flushed, greased and stored away ready for the next boating season. But as you’re going through the storage process in your head you pass a gas station and the question you ask yourself every year jumps to mind, “Should I be filling the fuel tank up? Or should I be leaving it almost empty?” What to do? This question has appeared on Forums, Facebook Groups and has been asked of Outboard Technicians since Noah strapped a two stroke on the Ark.


The following is a guide outlining the correct procedure surrounding storing fuel (petrol) in your boat fuel tank during the off-season.


1. Fill the tank up! I’m sure you don’t want to throw another 100 bucks of fuel in the boat only to have it sit there for six months but filling your tank up reduces the amount of air in the tank. Fuel tanks, whether they are above or below floor, will expand and contract due to varying temperatures. As they contract, they draw in air and moisture which then collects in your fuel tank. It makes perfect sense then that the less available space within the tank for air will greatly reduce the amount of moisture that can form inside your fuel tank.


2. Use a Fuel Stabiliser. In my opinion (and many others) using a fuel stabiliser at the end of the season once the tank is filled is a smart move. When fuel sits for extended periods of time it loses the light components due to evaporation causing the fuel to become heavier. This results in harder starting, rough idling, spark plug fouling and the possibility of piston damage and detonation. A fuel stabiliser helps to keep these light components in your fuel and ensures your fuel stores better and for longer. Many stabilisers claim that it will extend the life of the fuel for up to 12 months. How good is that! Just a tip - I’d be putting the stabiliser in first then adding your fuel. This will help to mix the stabiliser in more effectively.


So, it’s pretty simple really. Fill the tank up and use some fuel stabiliser, job done!


To grab yourself a fuel stabiliser, click here.

Comments (3)

2000 35hp Johnson

By: on 4 August 2019
Hi Outboard Spares, thinking I may have a CDI issue. The motor starts easy, runs a bit rough, has different volt variants going to coil packs, doesn't seem to make it worse when I take individual leads of when running, it stops when it warms, has no spark, but only takes a few minutes and it has spark again. Love to hear your thoughts. Cheers Scott

Outboard Spares Response
Hi Scott, Sounds very much like a power-pack issue to me. If this is the 3 cylinder model, they were notorious for having power-pack failures. You can check the stator output with a digital multimeter and DVA adaptor to confirm whether the stator has sufficient output, but given what you've told me about different voltage to the coils and the fact it stops running when it is warm, i'd be pretty confident your power-pack is the problem. Cheers

No fire on 2 and 6 after sitting up for winter

By: on 16 April 2019
200 mercury outboard. It starts and runs but won't accelerate. Used a spark tester and no fire on2 or 6. They come from two different switch box's, so I was wondering how to pin point the problem.

Outboard Spares Response
Hi, I'm pretty sure cylinders 2,4,6 are on one switchbox and 1,3,5 are on the others. Just check this, maybe I'm having a moment but I'm pretty sure this is the case. If I'm correct it is likely the switchbox or it could be stator, or trigger. To me though if it is always the same bank and same cylinders on that bank then most likely a switchbox or coils but it would be odd to all of a sudden have 2 faulty coils. I hope this helps. Cheers

Old fuel

By: on 8 March 2019
Filling the tank and using a stabiliser is a great tip. I am not sure what to do with the fuel in the carbies though. Had to pull the 3 carbies off my Yamaha V6 this season and 5 of the six main jets were blocked (gummed fuel). Is it OK to run the carbies out of fuel with a two stroke at the end of the season??

Outboard Spares Response
Generally it's not good practice to run the outboard out of petrol as petrol (as well as the oil ) is a lubricant for the pistons and bores. I'd suggest undoing the drain screws on the bowls and draining the fuel this way onto an old rag or small container. Cheers

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