Water Pump Impeller

[NikTheGeek]

My winter lift out came to 15k all up. Im still smarting.

My whole boat, engine and trailer only cost that new!

a few years ago now mind, but still...

[BruceK]

Well my starboard engine overheated 30 miles out. Limped back on port engine to Caernafon negotiating the Swellies and Menai on one engine and virtually no steering as the hydraulic assist pump is on starboard engine so any imput required significant effort. New impeller shredded a vane. Just one mind.. Must have picked up a plastic bag. Sods law but proof positive that no impeller means no effing engine.

[Bigplumbs]

Well my starboard engine overheated 30 miles out. Limped back on port engine to Caernafon negotiating the Swellies and Menai on one engine and virtually no steering as the hydraulic assist pump is on starboard engine so any imput required significant effort. New impeller shredded a vane. Just one mind.. Must have picked up a plastic bag. Sods law but proof positive that no impeller means no effing engine.

When did this happen ?

[BruceK]

Today.

[Bigplumbs]

Today.

Bummer not a good start to the season

[lewlew100]

Rotten luck Bruce, it just goes to show just how much plastic there is in the sea, I do hope that is the end of your problems for the rest of the season, and at least it does sound like a fairly inexpensive fix this time. -Plastic debrist is now a world wide problem - and TOTALLY unnecessary. Geoff.

[BruceK]

All sorted. Amanzi held a steady cruise of 26knts and the temps were spoton. For once I am grateful its Volvo and not mercruiser legs. Just once mind and probably never again

[lewlew100]

Good result. Geoff.

[BruceK]

It shredded again! Cant work this one out

Last year before lift out everything ran fine. Engine temps were good. Boat was on hard for 4 months now over winter. On drop in took her for a spin and everything fine. Changed impeller and checked she was pumping. Boat stood for two days and next outing she had shredded the impeller within a couple miles. Changed impeller and checked she was pumping. Ran boat and temps fine. Boat stood for 2 days and she shredded the impeller within 2 miles on next trip.

I have managed to get all impeller bits out on both occasions. When I take the raw water feed off water gushes out so no blockages between leg and pump. Impeller sits 1.5 inch above waterline so does not have to lift water far. I have removed the hose downstream from the basket and a fair amount of water gushed out then stopped. (yes it scalded my hand trying to catch any wayward impeller bits that might have got past the basket...doh!)
Now the unscientific bit. On the downstream hose I can both blow and suck reasonably freely with the sound of gurgling water from the ?transom? (difficult to be sure when working alone) I wouldn't have thought this possible with my 290 legs that vent below the cavitation plate. However there are no leaks in the cooling system.
The legs have been off for a Volvo dealer service and replaced by them, when running the engine there is no unusual exhaust note.
Pump housing looks good with some wear but nothing unusual and the impeller makes a good tight fit all round.
When opening the basket the basket cap isn't sticking on requiring lifting off with the aid of a pair of pliers which indicates some loss in vacuum.

[BruceK]

After stripping out all hoses etc and finding nothing I returned to the pump. Turned out air was leaking past the impeller shaft seal. Not a lot mind you could still hold a vacuum for a short while but obviously it was enough at high revs to cause an airlock. Replaced the pump and will have the old one resealed and refurbished as spare