M25XP seawater pump will not pump - SailNet Community

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Old 04-18-2010
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M25XP seawater pump will not pump

I started my engine at the boat yard today and the seawater pump would not pick up water with the hose hooked to the riser. Disconected it pumps like mad all the way thru the heat exchanger and all hoses. With the hose hooked to the muffler and disconnected from the raw water pump I can blow freely thru the hose thru the heat exchanger and into the exhaust system.

Ideas?
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Old 04-18-2010
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Did you try it again afterwards? The reason that I ask is that if you have airlocked the pump, the riser can add just enough backpressure so that the pump can't push the air bubble through and get to water.
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Old 04-18-2010
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Thanks I will try again tomorrow
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Thanks I will try again tomorrow
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Old 04-20-2010
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"hose hooked to the riser?" What does that mean? You shouldn't be connecting a hose directly, but rather using a bucket of water for the pump inlet. The vane pumps can pick up only a few feet of head and should self prime.

What pump? You could have a Sherwood or an Oberdorfer. If it's the latter, check the faceplate - it needs to be smooth. The inside of the faceplates gets gouged over time and either need to be replaced or serviced to flat.
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By hooked to the riser I meant the hose was attached to the exhaust riser. I always pull water from a bucket.
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Old 04-22-2010
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Question Hours and Wear

Quote:
Originally Posted by anemoneii View Post
By hooked to the riser I meant the hose was attached to the exhaust riser. I always pull water from a bucket.
If you "uncloak" and fill in your boat model and year and sailing venue, this can sometimes allow more focused help.
For instance, I have an '88 M25XP. At about 1900 hours we replaced the entire Oberdorfer raw water pump -- not because the impeller was bad, but due to wear in the cast pump chamber. In our particular river there is significant silt present year around in the water and it is actually a very fine but "sharp" sand of volcanic origin.

Previously we once had to machine the grooves out of the cover plate, about a decade ago, and found that in the last year even a new impeller would not move water as fast as expected.
With the wearing away of the metal, the pump chamber gets a bit larger inside and the rubber vanes start losing some of their sealing and pumping ability.

Perhaps not a problem for you, but an example of why some parts (sometimes) do need to be replaced.

So, how may hours on yours? Water siltation a problem?

Regards,
L
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