Yanmar Seawater Pump Failure When Sailing

[revere]

4JH4E Yanmar
Does anyone have any suggestions on what the solution may be for the following problem.

I'm sailing at 6 kn with engine off. Need to start engine to take sails down. Seawater pump fails to draw water up into seawater filter. I checked: impeller (new), thru hull strainer, valve and hose for blockage - all clear.

Seawater pump operates properly if boat is not moving under sail. Seawater pump is only 4 years old.

I noticed inlet thru hull strainer has a scoop (clamshell) that faces aft creating a vacuum. Shouldn't it being facing forward to help assist pump. I talked to other boaters and their scoop is facing aft also. Doesn't make sense.

Any suggests would be great full

Revere

[Stu Jackson]

Why External Strainers are a Bad Idea 101 (Maine Sail) http://forums.catalina.sailboatowner...d.php?t=124964

[a64pilot]

You shouldn’t have a scoop at all. For air conditioning it’s OK but never for an engine.’if facing forward it can flood your engine with seawater, not real likely maybe cause I doubt you go fast enough to generate enough pressure, but you may.

You shouldn’t have a scoop at all on an engine, just a round disk full of holes, or no strainer at all.

[shakey doug]

Pump face plate or cam worn, try turning face plate over.

[NYSail]

Yes has to face aft so it doesn’t flood engine when under sail. Motor boats face forward as they move only when engine is in use......
I have this on the same engine and will be removing it. They fill with debris and muscles. Bit I never had the problem you are having......is you strainer tight? Could be loosing its prime



Greg

[revere]

Thanks everyone for the reply. I will be removing the scoop by grinding the slots open. Probably my pump is getting worn and not able to overcome the vacuum created by the scoop. Probably need to rebuild the pump also.

[Jackz]

I had exact thing happen on my Yanmar 3JH5E in Leopard 44. Sailing caused venturi effect draining water from strainers, and upon start up there was no vacuum so we burnt impellers. Solution was to move strainers lower and shorten the amount of hose going to the strainer, thus causing significantly less travel and lift of the water. I also replaced seawater pumps to be sure I could sleep at night! About 50 hours later no problems, even after sailing in rough seas. Plenty of water circulating.

[out42]

Same problem on my 3ym30's last year. Likely cause is a face plate leak around the impeller after a few years. Same happens behind the impeller on the base plate. You can replace a faceplate but a scored base late means a new pump body, I suspect.

[Cheechako]

Is your strainer above waterline? I guess it must be with your problem. Does it have to be? One of my boats had a slotted scoop. I had no issues at all...

[shakey doug]

Quickest, Cheapest and Easiest things first.

[Jim Cate]

Originally Posted by out42

Same problem on my 3ym30's last year. Likely cause is a face plate leak around the impeller after a few years. Same happens behind the impeller on the base plate. You can replace a faceplate but a scored base late means a new pump body, I suspect.

I don't know if this is universal, but our Johnson sea water pump has a replaceable wear plate behind the impeller. Fairly inexpensive, easy to replace.

And yes, wear in both of these places can lead to the symptoms described.

Jim

[a64pilot]

I replaced my external strainers with these.
You can Dive the boat and remove the pin and open the strainer and clean it out, then close it back up.
Sailboats should have “Round” strainers in my opinion, not scoops of any kind, sure why not a scoop for a Watermaker, but then why have a scoop?
https://www.groco.net/products/raw-w...ner/rsc-series

[blubaju]

Originally Posted by revere

4JH4E Yanmar
Does anyone have any suggestions on what the solution may be for the following problem.

I'm sailing at 6 kn with engine off. Need to start engine to take sails down. Seawater pump fails to draw water up into seawater filter. I checked: impeller (new), thru hull strainer, valve and hose for blockage - all clear.

Seawater pump operates properly if boat is not moving under sail. Seawater pump is only 4 years old.

I noticed inlet thru hull strainer has a scoop (clamshell) that faces aft creating a vacuum. Shouldn't it being facing forward to help assist pump. I talked to other boaters and their scoop is facing aft also. Doesn't make sense.

Any suggests would be great full

Revere

Similar problem: everytime sailing became fun, >7kn, an impeller died. The bowwave had its deepest point at the inlet. Moved the intakes(catamaran) below the bridgedeck and 20cm lower. No more problems since

[sailcrazy]

Our 4JH-TE has a slotted scoop on it(factory). Had a problem once....turned out the slots were full of growth. Cleaned them out and never a problem since-but every time I dive on the boat I scrap those slots clean! Oh...the scoop faces forward.