Raw water pump issues on Yanmar 2gm20f

[aquaslav]

had the same kind of problem on one of two 2gmFC's on my FP catamaran. Yanmar repair guys spent lots of time on it (time=$s). Eventually removed the in-line strainer and the water began to flow! Replaced the strainer and it still works fine.

[NoQuarter79]

We were having such a good trip from Ocracoke to here. The boat was running beautifully until now. We just want to get back underway. I would love to run aground right now.

[LLizzard]

I don't claim to be an expert, but it appears in the pic to me that your pump is clearly worn. There looks to be a wear pattern in the body beneath the impeller. Also, where the body compresses the impeller should be a concentric arc to create vacuum. In the pic, yours appears to go up and down like a roller coaster, probably inhibiting performance.

Also, I see a nick in the machined surface where the gasket and cover plate seal. Looks like it could have been caused by someone using a screw driver to try and pry out the impeller. NEVER remove an impeller in this manor as it damages the surface of the pump impeding proper seal. Instead you can use an impeller puller, or use pliers or vice grips to pull straight up.

If I'm you, I'd either try buying a new cover plate or smooth the outside of the existing plate and flip it. But you have that nick in the sealing surface, so perhaps you add some gasket sealant/ silicone, in addition to a new gasket. If that fails, I think a new pump is in order IMHO. Even if you get it to work marginally, it could stop anytime given the above. $200 is cheap compared to a new engine. You could also take it to a pump rebuilder to see what they think, but the new pump might be cheaper.

Good idea on the zip tie to compress the impeller. I've been using a hose clamp for 20 years to do that but a zip tie sounds easier to put on and cut off.

[01kiwijohn]

Pump looks pretty good here. To close up the two lugs, on the shaft end, pull the impeller. Squeeze the end, carefully , very carefully, until the fit into the impeller is just snug. I've salvaged an owner's pump just like yours, before, using vice grips. Reinstall the impeller, using the 'zip tie' method mentioned previously. Coat liberally with lube (Vaseline works fine too).
Check output with hose disconnected, briefly.
Then move downwards to the exchanger output.
Next, the fitting and hose to the exhaust elbow.
Finally, take the exhaust hose off and scratch around up inside to clear the water discharge port there. Use a coat hanger, cycle spoke, piece of wire cable, whatever you can improvise.
That pump generates very little pressure, and will not 'blow ' the passages clear. Must work then.

[jhulmer]

Originally Posted by NoQuarter79

Would we see the collapsing of the hoses? Because we don't see anything like that and they all feel very strong.

Not really, we couldn't tell, but we decide to change the hoses because we could find anything else. They weren't expensive and after this solved the problem we started examining the old hoses. The raw water hose from the seacock had the inside lining of the hose separate from the wall of the hose and would flap down when the flow increased.

Yet another lesson learned: change old hoses regardless of how they look outside.

You could test this by disconnecting the output hose on the raw water pump while the engine is running and rev up the engine to see if the water increases flow or slows.

Hope this helps
Jim

[jamhass]

Thanks for posting the solution.

[jhulmer]

OH AND I ALMOST FORGOT!

I had that engine for 15 years (2GM20f) and one thing that I had a problem with as it got some age on it was the v-pulley on the raw water pump would come loose form the vibration.

There is a "D" hole in the pulley that fits the shaft that has a flat on one side.

When the pulley gets loose it will work on that "D" hole until it makes it a round hole and the pulley will spin and the impeller won't turn.

Happened to me on a long coastal cruise and I had to improvise by putting a thick washer on and tightening the hell out of the nut to provide a friction lock until I got to a Yanmar dealer. it worked for the remainder of the trip.

You will have to remove the pull nut to check that the "D-hole" is good or bad.

[Sailorman Ed]

Does anyone have a pen and inexpensive source for a replacement Johnson pump?
The F4b903 appears to have a slightly different flange. While I have rebuilt both of mine, I would like to carry a spare.
Also, a pen for the pump pulley as mine has been bent.

[DeepFrz]

Any progress on this problem that you would like to share with the forum?

[lockie]

I have the same pump and have successfully refurbed it myself. But I was still stumped a couple of years ago by an overheating problem that I could not solve despite doing all the right things. Finally I removed the inlet hose and shoved a long screwdriver down it, and out fell some hard marine growth that had proved impossible to otherwise detect. So replacing all the hoses, even if they look fine, can be worthwhile.


Cheers, Graeme