Weak raw water pressure

[grant.mckenzie]

https://moyermarine.com/product/mmi-502-flange-pump-csob_00_365/

Hi I have one of the linked pumps on a raw water cooled engine, pump was new about 5 years ago, never changed the impeller. I'd say about 10 hours per year on the engine.

Boat is out of the water, I am preparing to launch. Had trouble starting engine this year maybe a total of a few minutes running the engine in the starter, for most of that time I forgot to have the pump inlet hose in a bucket of water.

Engine is running now, but water pressure is close to zero on the inlet and outlet from the pump - I can put my thumb over it without problem.

I took the impeller out and with a quick inspection it looks very good - no broken vanes or decay of any sort.

Any thoughts? My only idea is to change the impeller, obvious I know...

Thanks.

[ndutton]

I would change the impeller because of its age alone. Try priming the pump the next time you start the engine.

[grant.mckenzie]

Thanks Neil - how to prime? Do I just connect a hose to the intake, elevate it somehow and pour in water from a funnel?

[ndutton]

I would place a 5 gallon bucket filled with water a little above the engine and a temporary hose long enough to reach the pump intake. With one end of the hose in the bucket, start a siphon by sucking on the other end of the hose and when the siphon starts, immediately connect it to the pump intake. Start the engine and see if the flow is improved. With 5 gallons there is maybe a couple of minutes run time at idle. Shut the engine down before the bucket runs dry and connect the pump to the thru-hull as it should be and start up again (assumes you are in the water).

Please report back on the result.

[grant.mckenzie]

Hi - that resolved the issue thanks.