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Discussion Starter · #1 ·
I’ve noticed on my new (to me) boat that the raw water pump doesn’t prime unless I really rev up the motor. After that, it belches water at regular intervals at idle and there seems to be a steady stream of water in the exhaust at 2000 RPM and above. The idiot light for overheating is not coming on.

Here’s what I’ve done so far.

The engine is a 2010 Yanmar 2YM15 SailDrive

I replaced the impeller, although the old impeller looked fine.

I removed the hose from the pump on the intake side and blasted water through it (toward the saildrive intake) - there was no back pressure, so there doesn’t appear to be any obstruction on the inta.

I connected a length of hose to the intake side of the pump and dunked the other end in a bucket of water. The pump still didn’t self prime until I revved up the engine. After that, I got the usual belching of water, but it didn’t seem to be emptying the bucket very fast; (Although I really don’t know how much water it should be moving).

It sure seems like it’s the pump, but I thought I’d seek a bit of advice before dropping 3 Benjamins on a new one.

Any information is appreciated.
 

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The raw water pumps are a wear item. It just may be shot. Is the cover fairly scored inside, where it contacts the impeller?
 

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Discussion Starter · #3 ·
I’d say the inside of the cover looks more polished than scored, but I guess it’s a fine line between polished and scored.

Does 10 years sound like about the right lifespan for a raw water pump?
 

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Saildrive pumps usually won't prime using a hose. The boat must be in the water for them to work correctly. Check the owners manual. They need positive suction.
 

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Does 10 years sound like about the right lifespan for a raw water pump?
I'm sure different pumps and hours will vary that answer, but I've never had one come close. 4-5 years more likely. I carry a spare, for that reason.
 

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Discussion Starter · #6 ·
Saildrive pumps usually won't prime using a hose. The boat must be in the water for them to work correctly. Check the owners manual. They need positive suction.
Thanks for this info. I’m having trouble figuring out how to create positive suction each time the motor is started and when winterizing. Since the pump is on the engine and not in the lower unit, the hoses in the path from the saildrive to the pump won’t always be filled with water, particularly after the boat has been out of the water.
 

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Sure sounds like wear in the pump housing/cover. Sometimes filing the cover smooth will close the clearances up enough for the pump to work better. if that plus a new impeller don't fix things, then a new pump is probably the way to go.
 

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There's a vacuum valve on top of the hose loop that might be sticking. Regardless of the current situation it should be always checked and lubed if not replaced. If stuck, it can suck water back into the engine when started again. But ten years is a lot of wear only if it saw a lot of use. Love Yanmars, but the Sweds make a raw water pump that can leak. It's not relative but worth a look and see. Look also at the recommended lift of volume and how high the water goes in the loop. Look at the strainer and know it's clean and no check valves were installed be Elmer which are a variable.
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Discussion Starter · #9 ·
There's a vacuum valve on top of the hose loop that might be sticking. Regardless of the current situation it should be always checked and lubed if not replaced. If stuck, it can suck water back into the engine when started again. But ten years is a lot of wear only if it saw a lot of use. Love Yanmars, but the Sweds make a raw water pump that can leak. It's not relative but worth a look and see. Look also at the recommended lift of volume and how high the water goes in the loop. Look at the strainer and know it's clean and no check valves were installed be Elmer which are a variable. View attachment 140755 View attachment 140755
Can you explain that a bit more? On mine, there's a hose from the SailDrive seacock to the strainer, then there's a hose from the strainer to the intake of the pump. I don't see a valve in there anywhere. Should there be?
 

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Discussion Starter · #10 ·
Well, I ended up replacing the pump. It seems to have done the trick, but I'm wondering...

Since the boat is drysailed, the strainer and the hose leading to the pump will always be empty when first starting the engine. Even if it does prime, won't it be subject to undue wear while running dry until it gets water? I'm wondering if I should concoct a way to release the air in the intake path before starting the engine. Thoughts on that?
 

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If I was worried about it running dry, while priming, I'd dose it with a shot of glycerin or dish soap. Pull the top hose to do it.
 
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