Sea Strainer won't Prime

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Triggen

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Relatively new owner. Just got her on the water (27 foot wooden cruiser with 38HP Westerbeke). I started to see high temps so checked the water flow. Initially I though I had a blocked externally strainer, but have confirmed it's clear, however, the striker is just at or above the water line and it's not pushing enough water into the strainer on it's own. Is it likely an impeller or water pump? TY!
 
if the boat has been out of the water, can get an airlock if the strainer is above the waterline. I used to get this problem on my old boat.
I used to get a container of water, and opened the trainer, added water, put top back on and restart. All was good. No problems when left in the water
 
Your impeller won't 'suck' as well when it is dry as when it is wet, especially if either the impeller or the pump is worn. If other techniques fail, before attempting starting it pour some water into the pump (by taking the inlet pipe off the pump or strainer) or removing the impeller and greasing or throughly wetting it to help it prime the system.

As you are asking whether it could be the impeller, it implies you haven't inspected it, and this is very much worth doing (and being familiar with doing) anyway. You will be removing the impellor, checking for signs of wear of the tips of the blades, any broken or permanently deformed blades, and manually flexing the blades to see if there are any cracks in the roots of the blades. Consider putting in a new impeller anyway to check, even if you don't see any problem, and keep the old one as a spare if it appears in OK condition. While you are checking/changing the impeller make sure the sealing O-ring or gasket is OK (though you will have had a water leak if the seal/gasket has previously failed or the cover plate become distorted).

As ChromeDome indicates, you may be sucking air in. The lids of strainers can sometimes fail to seal properly. Take it off, grease the thread or seal, and put back on, making sure the thread is not crossed and it is neither under nor over-tightened.
 
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chillee said:
if the boat has been out of the water, can get an airlock if the strainer is above the waterline. I used to get this problem on my old boat.
I used to get a container of water, and opened the trainer, added water, put top back on and restart. All was good. No problems when left in the water
Click to expand...
I don't understand why you would put water in your trainer. Surely you would get wet feet.:)
 
LittleSister said:
Your impeller won't 'suck' as well when it is dry as when it is wet, especially if either the impeller or the pump is worn. If other techniques fail, before attempting starting it pour some water into the pump (by taking the inlet pipe off the pump or strainer) or removing the impeller and greasing or throughly wetting it to help it prime the system.

As you are asking whether it could be the impeller, it implies you haven't inspected it, and this is very much worth doing (and being familiar with doing) anyway. You will be removing the impellor, checking for signs of wear of the tips of the blades, any broken or permanently deformed blades, and manually flexing the blades to see if there are any cracks in the roots of the blades. Consider putting in a new impeller anyway to check, even if you don't see any problem, and keep the old one as a spare if it appears in OK condition. While you are checking/changing the impeller make sure the sealing O-ring or gasket is OK (though you will have had a water leak if the seal/gasket has previously failed or the cover plate become distorted).

As ChromeDome indicates, you may be sucking air in. The lids of strainers can sometimes fail to seal properly. Take it off, grease the thread or seal, and put back on, making sure the thread is not crossed and it is neither under nor over-tightened.
Click to expand...
TY..very helpful!
 
chillee said:
if the boat has been out of the water, can get an airlock if the strainer is above the waterline. I used to get this problem on my old boat.
I used to get a container of water, and opened the trainer, added water, put top back on and restart. All was good. No problems when left in the water
Click to expand...

Just got back from the boat and this definitely worked and got some water flowing! It's still not as much as I'd like so will check the impeller and pump next. Thanks again!
 
Blocked heat exchanger.You say a new pump has been fitted . Perhaps bits of an old impeller are still in the pipes or there is calcium in the tubes - being an older vessel- which needs cleaning to allow better water flow.

Blocked exhaust elbow. I do not know the engine set up, but a build up of carbon deposits in this area greatly restricts flow; assuming the water is injected into the exhaust near the hot manifold.

Correct impeller( there could be a non stndd one fitted which is 0.5 mm thinner & air passes between it & the cover) It should touch the cover when assembled. You have a new pump, but I have had a loss of suction when the cover has worn slightly. This could suggest that if the last owner cut corners with impeller cost it may be a dodgy one. I have had this issue in the past & now stick with Volvo ones on my Volvo engine.
 
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alandalus11 said:
I don't understand why you would put water in your trainer. Surely you would get wet feet.:)
Click to expand...
They said it was just above the water line..
I should have been clearer I guess. I had a secondary strainer, before the main engine one. And because it was above the waterline, it sometimes got airlocked.
This was the one I could add water to, to prime the system
 
If it’s not the impeller, the strainer can draw air from its lid or cap. Check the seal I’d say.
 
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