fresh water intake problem -impeller already changed - Help!

[rustybucket]

Yes it would..

Yes, it absolutely would.

[brico]

If you have fuel cooler fitted just after the raw water pump I would check that there is no bunch of old broken off impeller blades blocking the flow of raw water through that cooler and into the heat exchanger.

I have exactly the same engines on my 1980 built 37 convertible and when I bought it back in 2014 one of the engines was steaming when run at WOT. When I opened up the pipes, I found 6 or 7 impeller blades stuck there and couple of zinc anodes.

The 'mechanic' that maintained the engines for that owner only replaced impellers, but never thought of looking where broken off impeller blades are. They are too big to pass through either of the fuel cooler or heat exchanger.

[Captain Ralph]

The 'mechanic' that maintained the engines

Dangerous guy with a wrench in his hand, not a proper marine tech.....
I would be aware of any other work he did on this boat.

[Captain Ralph]

Air coolers (TI's), main heat ex-changers, remote clutch oil coolers, TA air box coolers and more can restrict the raw water flow after the pump. But the smallest air leak before the pump will make you mad. Worse than clasping hoses before the pump (well almost).
Padded cells would be welcome sometimes.

[hack]

ok went down the 28th took hose off seacock ,removed strainer all plumbing , cleaned , installed new gaskets at all
fittings ,checked all clamps , reassembled strainer and plumbing in one piece put back in boat .
fired main up ,stainer filled in couple seconds (heck ya) took 20 mile cruise all performed well.
thanks for all advice ,everybodys time .

[dottieshusband]

Just my recent experience. I started my new Generator Thursday (50 hours on it), and the coolant belt immediately broke. Not to worry, NAPA matched it up and I fitted it. Started the Generator up, and the Sherwood GP910 squealed in horror... I could turn it by hand, but under the engine load, would slip terribly... long story short, the inlet grate had sucked up a Kroger bag..

[rwaldrop13]

Just my recent experience. I started my new Generator Thursday (50 hours on it), and the coolant belt immediately broke. Not to worry, NAPA matched it up and I fitted it. Started the Generator up, and the Sherwood GP910 squealed in horror... I could turn it by hand, but under the engine load, would slip terribly... long story short, the inlet grate had sucked up a Kroger bag..

When we bought Pau Hana last August, the Onan 20KW generator ran like a champ thru the survey, and Okeechobee transit. But while going into the first marina we had signed a lease with (and broke immediately on arrival, but that's another story) we sucked a strainer full of mud so the impeller ran dry for several minutes. We cleared the strainer and restarted the generator and it ran thru the weekend at our second (long term home) marina but would not restart after we shut it down. I pulled the impeller cap and it was missing ALL the vanes. I cleaned it out, replaced the impeller and ran water thru the generator. Still no joy on starting. Had to apply 3 shots of Ackroil to the heat exchanger cap to break thru the 20+ years of paint/rust to get it off and found all the vanes right at the cleanout end. I was able to flush with freshwater but nothing else came out. Just a learning process - and in the long run an easy fix once I knew where to look.

[yvella]

I had same issue come to find out the only difference was old had more vanes than the one I replaced it with. May have been your issue also.

[SEVEN]

ok went down the 28th took hose off seacock ,removed strainer all plumbing , cleaned , installed new gaskets at all
fittings ,checked all clamps , reassembled strainer and plumbing in one piece put back in boat .
fired main up ,stainer filled in couple seconds (heck ya) took 20 mile cruise all performed well.
thanks for all advice ,everybodys time .

Congratulations

[spartonboat1]

Sucking air is the normal issue. Even if you put the vanes in backwards they will quickly re-align the proper direction.

I'm guessing one of the hoses/fittings you took off is not sealed up good. For rubber hoses I like to heat them up nice and hot to soften them and then clamp the hose clamp down pretty hard on them. Old rubber hoses get hard and the hose clamp just doesn't have enough arse to clamp down on them.

Any pipes you took apart may need new gaskets and/or sealer.

Also, be sure to load the impeller up with soap or appropriate grease. If you put it in dry and have ran the engine you probably need to change the impeller. It takes about 10 secs of running dry to fry them.

Coat impellers and cavity with lube, before installing the impellers. Can use Dawn Detergent, but maybe better yet, go to a swimming pool outlet and purchase Alladin brand "Magic Lube", which is intended for swimming pool pumps, aka your impellers. [ #630-1 oz ] (other sizes?)

That's in reference to impeller lube. I use the Magic Lube for my impellers.

P.s., I boat on the Great Lakes, so store in the winter. I pull my impellers, shortly after hauling and when on the hard, every year. I inspect the impeller or impeller body for cracks, then store the impellers(s). Pulling the impellers avoids the impeller vanes taking a "set", while confined to the pump cavity.