What To Look For When Inspecting Your Water Pump

Author: Stuart Buckingham   Date Posted:27 April 2018 


Your outboards water pump is its main cooling mechanism, without it your engine would overheat in seconds leaving you bobbing around the ocean like a randomly positioned FAD. If you're someone who doesn't mind getting out the paddles on the odd occasion and getting a bit of exercise then perhaps this blog isn't for you but, if the idea of a 3km paddle back to the boat ramp isn't your thing, then please read on and see why inspecting your water pump is so important.


What does a typical water pump consist of? An outboards water pump usually consists of a rubber impeller, stainless steel cup or insert, wear plate and some gaskets and o-rings to seal everything together around and within a housing.


Impeller: It is the rubber impeller that causes the most grief. Being rubber, it only has a limited life and most engine manufacturers will recommend annual replacement of this part. Impellers have veins or blades that fold over and draw water through the water pump and force it up to the powerhead. It is at the point, where these veins fold, that becomes a weak point - especially when left sitting for extended periods without use.


Cup or Insert: The cup is the insert or liner within the water pump housing. It’s generally made from marine grade stainless steel and houses the impeller. Because the impeller spins within it, it is imperative that it is smooth and without scoring from sand or gravel and free of any wear marks seen from extended use. If your insert is worn, then it will shorten the life of the impeller so replacing it is a smart move.


Plate: While the insert sees the impeller spinning within it, the plate sees the impeller spinning on top of it. Also made of marine grade stainless steel, the plate like the insert, must be free from scoring and wear. Often the plate will develop circular grooves on it from the impeller and this is a sign it's time is almost up. If you can feel the grooves on the plate with your fingernail, then definitely replace it.


Gaskets and O-rings: Making sure that all your gaskets are intact, and your rubber o-rings have not perished, is also important. Water pressure may be lost if these parts are not up to scratch so checking them and replacing them if necessary is obviously good practice.


There are two types of approaches when it comes to boat maintenance; the ‘if it ain't broke don't fix it’ method and the ‘prevention is better than cure’ method. When it comes to water pumps and impellers the ‘prevention is better than cure’ approach will ensure you’re not left up the creek without a paddle, or in this case, out to sea without an outboard.


To shop our range of water pump parts, click here.


Comments (1)

It's not only the pump end that gives you grief.

By: on 27 April 2018
I was recently having endless problems with cooling of my engine. Then one day Stuart suggested after I had ordered my second pump overhaul kit in a week to have a look at the thermostat. It's really easy to get to and simple to test. In my case it did not solve my problem but that inspection did lead me directly to the real problem.

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