Perkins Loses Prime

[Janice]

Our T37 has a 4-108 perkins and we are having an intermittent problem
I am hoping one of you has experienced. Every once in a while it
looses is prime from the sea water cooling pump. Steve has to lossen
the front cover and bleed the air out to get the cooling water flowing
again.

Janice & Steve
Sailacious.com

[S/V_Surya]

Does it do this during operation or after having sat for a time? I go all winter out of the water and when relaunch it primes right away. Is this a new problem? All points to a worn impeller but still pump should be below water line and no prime required.
Hmmmmmm........

[Janice]

We are on cruising on the boat so the engine is run almost daily. It always happens while moving and this sometimes happens in rough seas, but not always.

[zeehag]

got an airleak somewhere......or impeller.....gooodluck

[jrd22]

"While moving." Do you mean sailing or is this happening while the engine is running. Have you changed the impeller since the overheating problem started? How old is the pump itself, could be worn?

[onestepcsy37]

also make sure there are no leaks coming into the pump - meaning the intake hoses or, more likely, the raw water filter. have you changed the seal on the raw water pump?

some boats 'bounce' the intake thru hull out of the water in mild or heavy seas and that would possibly inject some air into the system.

[shakey doug]

Face plate might have excess wear turn over or replace also check gasket thickness if not genuine one, newspaper thickness works well also put a smear of siicone or grease over cam securing screw.

Cheers, Shakey.

[jzk]

She said it always happens while moving and sometimes in rough seas. Where is the location on the hull of the water intake seacock? I bet that it comes out of the water when you heal and you loose the seal. Our rear airconditioner does this.

[s/v Jedi]

First step is to replace both impeller (again even is done recently) AND face plate. If the plate is thick enough, sand it flat again or turn it to use the other side after sanding any marks or text off it.

If that doesn't help, replace the pump and have the old one overhauled and add it to the spares locker.

Every impeller pump is self priming with very good lift capacity so when it doesn't something is worn or broken.

cheers,
Nick.

[Randyonr3]

Mine started giving me trouble and showed up on the tempeture guage in an over heating problem.. changed the impeller twice without any difference.. went to British Marine in Oakland and after they inspected it, found the shaft and housing was worn.. didnt like the price of the new unit but after installing it, the problem was gone......

[s/v Jedi]

Originally Posted by Randyonr3

Mine started giving me trouble and showed up on the tempeture guage in an over heating problem.. changed the impeller twice without any difference.. went to British Marine in Oakland and after they inspected it, found the shaft and housing was worn.. didnt like the price of the new unit but after installing it, the problem was gone......

Wow... that means you have been using the pump for a long time with less than optimal flow. I say that because the compression-block inside (that compresses the impeller blades as they pass) wears out way before the shaft or housing!

cheers,
Nick.

[OTG263]

I would like to continue this thread if I may. You all are describing a problem I have with my Perkins 4108.

When motoring in rough conditions or even moderate swells, my raw water intake sometimes sucks air, so that I end up with an air bubble in the raw water strainer, which the raw water impellor will not suck thru. Resulting in the engine overheating.

To get her running again, I close the seacock, open the lid on the stainer to bleed the air out, then close it up again. At this point I usually prime the impellor with soapy water just to get things moving.

In rougher conditions, this is a bit of a pain. And likely only resolves the issue until the next time it sucks air.

So what I'm wondering is, is there a way to permanently resolve this issue? Should my impellor be capable of sucking the air thru? I'm at a loss. The only thing I can really think of is to move the thru-hull to another position in the hull, something down lower. But I can't imagine that the boat, a Morgan 38, would have such a design flaw.

Any thoughts?

[Dynamo1181]

I would think that you have excessive wear on the front cover as well as the rear wear plate of the Jabsco raw water pump. When mine begins to wear, I can have the same issues. Rebuild that pump and I bet your problems will be solved.
A

[GordMay]

Greetings and welcome aboard the CF, OTG263.

[OTG263]

Dynamo, I'm running a Sherwood pump, but your point is well taken. Although I have replaced several parts of the pump over the past 2 years (bearings and cam, and have polished the outer wear plate), in the end I have to admit that I don't trust it to perform. I think at this point I shall install a new one, then completely rebuild the old one for the experience and use as a spare.

As you can see, I've been dealing with this particular problem over the last few years. It's only been in the last few months that I realized that there was an air pocket in the strainer and the pump wasn't strong enough to clear it. We'll see what the new one does for the situation. Thanks

And thanks to you Gord for the welcome to the forum.

Cheers!