engine sea water pump not priming

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superboots

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After launch sea water pump had to be primed from strainer with sea cock closed to get it to flow. Same problem re-occurred after exhaust elbow replaced only this time mechanic revved engine for some minutes and then when primed pump started to leak from seal. I had changed the impeller - which was not damaged but that was not the problem. No leaks from any of the pipe work. Any ideas why this is happening? If I have to replace pump should I fit a larger capacity pump just to be on the safe side. Engine is VP tmd22p
 
The clue may be in your question. If water leaked out from the shaft seal, air can leak in. This will prevent pump priming, as will any air leak on the suction side, e.g. Lid seal on the strainer, hoses onto hose tails not tight, pump cover plate gasket/O-ring.
 
I had this problem after I fitted a new plastic strainer above the waterline - Vaseline around the threads on the screw on cap sorted it + making a wooden 'spanner' for the lid to make it easier to close and open easily.
 
Blipping the throttle a couple of times should be sufficient to get the exhaust flow going if the water lines have been drained down e.g. after lifiting out, and will not do the engine any harm.

Revving the engine for some minutes is not a great idea, even with a Speedseal Life fitted, and if this is necessary you need to find the source of the air leak sooner rather than later. Vyv has already nailed the likely issue.

Richard
 
Always grease the impeller vanes and especially ends with waterproof grease before fitting.
It seals those tiny gaps and enables the pump to prime without difficulty.

Before anyone says, no the grease doesn't do the vanes any harm at all as they're made of a rubber (neoprene IIRC) that isn't affected by it. No need to use vaseline.

I've been doing this for years with no ill effects, after experiencing a similar problem with priming after replacing with a new impeller. Nothing else worked. I tried part filling the system with water, coating the blades with fairy liquid etc but only grease sorted it in the end.
 
Thanks for the advice. Will use plenty of grease when the pump is returned with new seal. It would not suck before the seal failed so don't think that was the main cause. Maybe just wear on pump surface or end plate.
 
superboots said:
After launch sea water pump had to be primed from strainer with sea cock closed to get it to flow. Same problem re-occurred after exhaust elbow replaced only this time mechanic revved engine for some minutes and then when primed pump started to leak from seal. I had changed the impeller - which was not damaged but that was not the problem. No leaks from any of the pipe work. Any ideas why this is happening? If I have to replace pump should I fit a larger capacity pump just to be on the safe side. Engine is VP tmd22p
Click to expand...

I had this problem after doing any job on the raw water circuit. Turned out it was the Volvo Penta black screw-lid on the water strainer not sealing well. I fixed the problem by fitting a clear perspex cover to the VP strainer which seals much better and i don't need to remover the cover to check the strainer which avoids introducing air into the system.

Www.solocoastalsailing.co.uk
 
Don't know about Volvo but had similar problem with a Yanmar 2GM20f pump tried everything to cure it, impellors, speadseal, moved strainer lower down into bilge, flatted the face plate etc eventually found that the back of pump housing had worn unevenly mainly around impellor hub. Reluctantly I had to replace the complete pump but it cured the problem immediately and no further trouble for the last 2 years.
I dry out on most tides which doesn't help.
Pete
 
Once the pump has primed, how good is the exhaust water flow?
I spent months tracking a system with poor priming and poor water flow once primed. Every part of the water system was apart at some point with two raw water pumps, Strainer, Speedseal, impellers, pump shaft seals.....
Finally bought a new pump -problems all solved immediately.
24 year of VO MS31A
 
I had this problem and as someone else said the problem was a worn faceplate, solved immediately by reversing the plate and long term by replacing it with a speedseal cover which has a bearing within it that prolongs the impeller life too.
 
I'm a bit worried about the cooling system. Previously ovrrheated at high rpm. Assummed this to be a slipping belt -it was loose and burned so now replaced. Also flushed heat exchanger but no sign of blockage or dirt. Exhaust elbow now replaced. When the pump comes back with a new seal will have a sea trial but I suspect pump needs replacing. Wondering whether the fit a bigger pump or would this cause a problem for the water lock? Previously I through water low was low.
 
superboots
Assuming that the pump was fitted as standard by the engine manufacturer it should be man enough for the job (if it is working to spec). When I decided to replaced my water pump as it was badly worn I could have cobbled in a different pump or even fitted an electric one much cheaper than the real thing, but keeping it standard saves experimenting with a different system and when I eventually sell the boat it's what a new owner would expect to see.
Can you compare the output from your pump with another boat fitted with the same engine ?
pete
 
Last edited:
pete said:
Don't know about Volvo but had similar problem with a Yanmar 2GM20f pump tried everything to cure it, impellors, speadseal, moved strainer lower down into bilge, flatted the face plate etc eventually found that the back of pump housing had worn unevenly mainly around impellor hub. Reluctantly I had to replace the complete pump but it cured the problem immediately and no further trouble for the last 2 years.
I dry out on most tides which doesn't help.
Pete
Click to expand...

Same here! Tried all the usual solutions till it let me down completely in the Harbour enterance and I had no choice but to push on to the mooring with steam pumping from the exhaust and the overheat alarm ensuring every on the dock didn't miss the show.
After that a new pump was the only answer. Could have damaged the engine but no problems since.
 
I normally prime the pump by filling the strainer. These pumps are great for water, not really designed for air.
They can take ages to fill a big strainer, even if working perfectly.
Unless I get a drying mooring, I can't see it as an issue.
 
Pump refitted after seal changed. No improvement in performance checked hoses and strainer but at low revs not chucking much water out the back so will get a new pump. How can I find out the non-volvo pent a replacement item. I've been told its not a jabsco so could be Johnson. Here in turkey the VP replacement is astrometically expensive -has to be ordered specially from abroad as not in stock and is likely yo take 6 weeks. Cheaper to fly back to the uk and buy there!
 
You could check it's not a blockage of heat exchanger, exhaust elbow etc...
Can you test the pump disconnected from the output hose, driving it with a cordless drill or something?
 
superboots said:
After launch sea water pump had to be primed from strainer with sea cock closed to get it to flow. Same problem re-occurred after exhaust elbow replaced only this time mechanic revved engine for some minutes and then when primed pump started to leak from seal. I had changed the impeller - which was not damaged but that was not the problem. No leaks from any of the pipe work. Any ideas why this is happening? If I have to replace pump should I fit a larger capacity pump just to be on the safe side. Engine is VP tmd22p
Click to expand...

The jabsco manual says its a 29540-1001 For the VP TMD22/SX which is the nearest in my manual

Which is this pump

https://www.jabscoshop.com/spare-parts/default.aspx?code=29540-1001
 
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