SCW pump issue

[Ken13559]

Had a small leak at shaft of Sea Cooling Water pump (Johnson). Took it out to change the lip seal, impeller and cover o-ring.
Just today run the engine and the exhaust (underwater) sounds very funny.
Spent hours tracing cooling water from intake thru to Mixing Elbow. Everything looks right just that water isn't flowing to Mixing Elbow. Even open up heat exchanger and mixing elbow to check! Last straw, put in a spare complete pump and it works! Had a relook at the old repaired pump and now suspect the pump cover is wore such that a new o-ring created a gap between cover and impeller thus short circuiting the pumping action.
What's your thought on this?

 

[SG]

Our raw water pump body after about 2000 hours showed noticable erosion on the surfaces where the impeller rubs. You could be correct.

 

[Ken13559]

What if I order a new cover to replace the wore out one?
Would that work?
I do see some wore surface on the cover.

 

[SG]

Can you flip the cover over? We did that to turn the smooth side toward th impeller.

 

[Ken13559]

Can you flip the cover over? We did that to turn the smooth side toward th impeller.

Ah ha! Why didn't I think of that!? Thanks! Will give it a try.

 

[LeslieTroyer]

If you can’t flip - some have stamped #’s on the outside, you can resurface the cover with a piece of glass and wet dry sanding paper. Start at 220 and work up to 480.

 

[Ken13559]

If you can’t flip - some have stamped #’s on the outside, you can resurface the cover with a piece of glass and wet dry sanding paper. Start at 220 and work up to 480.

If flip works, I'll send down the scored / impeller side. Thanks.

 

[SG]

You would just use the cover plate upside down?

 

[Ken13559]

You would just use the cover plate upside down?

Yes did that and it works!! Doubt I'll sand the wore side as it looks to need slot of sanding to flatten it. So flipping the cover over is good. Thanks all

 

[MitchM]

if it's just the cover --- check out the Speed Seal pump covers which are designed to replace the stupid yan mar design: trapezoidal non flippable raw water pump covers, held on with 5 teeny little weird pitch acres that cannot be retired by a magnet when you drop them into the bilge. i think speed seal makes them for other brands of pump. the speed seal has beautiful big knurled knobs .

 

[Ken13559]

On 2gm20f the pump cover faces the engine hence Speed Seal does no good in such situation.
I could mod the pump by using the 3YM30 bracket and turning the pump to face out but that'll be more work than I plan to do now.

 

[Ken Cross]

I once had an impeller where the bronze center part delaminated from the rubber. Net result the vanes didn't spin with the shaft. A new impeller fixed it.

Ken

 

[WayneH]

Pulled into a marina for an overnight stay. Engine running fine, water puking out the exhaust. The next morning, no water in the exhaust. I suspect the the water pump isn't working because that's what is usually the problem. Get the cover off the pump and see little nubs where the vanes are supposed to be. Evidently, it was just failing when we came in and the pump was moving enough water to keep everything cool. But not enough vanes to pick up suction again. Getting all the pieces out of the hose to the heat exchanger was fun, NOT.