Yanmar water pump woes

[snowleopard]

the water pump on one of my raw-water cooled 3GM30s refuses to suck. if i prime it by pouring water in and reconnecting the hose, all is well but if i start it dry nothing comes through. also it occasionally stops pumping at sea in rough conditions. i have tried a new impeller (genuine yanmar) and the speedseal cover is not worn.

does anyone have experience of this problem and how to solve it? i understand a replacement will leave no change from 300 beer vouchers.

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[claudio]

I know it sounds obvious but have you checked the inlet hose to make sure its not leaking and letting air in ?
Has the route of the hose been changed, is it blocked ?
It sounds to me that there isn't enough suction to prime the pump.

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[claudio]

I know it sounds obvious but have you checked the inlet hose to make sure its not leaking and letting air in ?
Has the route of the hose been changed, is it blocked ?
It sounds to me that there isn't enough suction to prime the pump.

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[claudio]

I know it sounds obvious but have you checked the inlet hose to make sure its not leaking and letting air in ?
Has the route of the hose been changed, is it blocked ?
It sounds to me that there isn't enough suction to prime the pump.

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[claudio]

I don't know what happened there, we've somehow got the post in triplicate ?

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[bob_tyler]

Posting replies is now very slow. You probably thought that it was not going through as you had to wait so long and clicked three times.

You have to be very patient these days

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[claudio]

Thanks, I'll be more patient in future. /forums/images/icons/smile.gif

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[paulrossall]

I have had a similar problem with my 2GM20 (raw water cooled) this last season which has the same pump as your engine. I had the overheat alarm come on in rough weather on a number of ocasions. Once or twice there were small amounts of sea weed in the strainer which is screwed onto the seacock, but I don't think that caused the problem. Impeller was new at beginning of season and engine has only done 1000 hours. If I take the water intake pipe off the bottom of the pump water pours out so my problem must be the pump onwards. I intend to dismantle the pump and inspect it to see if I can find any undue wear, but did so last year and did not find any. I also intend to take out and test the thermostat.I will also measure the volume of water being pumped.
When you assembled the pump did you smear the impeller with grease as the manual instructs? I suspect this helps to make a good seal which should aid priming. Have you looked on the Yanmar help web site as I suspect the problem has been discussed there?
<A target="_blank" HREF=http://yanmarhelp.com/msgboard.mv?>http://yanmarhelp.com/msgboard.mv?</A>

<hr width=100% size=1>" there is nothing-absolutely nothing-half so much worth doing as simply messing about in boats".

 

[Birdseye]

assuming you have checked for air leaks on the inlet side, problem most likely is wear to the face and back plate which allows air to be sucked in through the engine block and exhaust. you might make some improvement by turning the face plate so the unworn outer face is inside - make sure its clean and smooth etc. however, if wear is the prob then it is likely that the back is also worn. options are a new pump, or get the old one machined back to tolerance. cellar marine at porthallow did the latter for me and made a good and economic job of it. talk to john skewes. he deals with too many fishermen to survive taking the "bolt on a new one approach"

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[Hunter34]

I had very nearly the same problem on my 22.5hp 3GMF.
After much messing I discovered it was a blockage in the raw water strainer which on my boat is midway between the thu hull and the pump.If air was allowed into the hose ie when engine stopped or heeled over, the pump couldnt generate enough suction to prime itslef because of the blockage in the strainer.If I primed it myself it worked.
Might be worth bypassing the strainer and seeing if it helps.
I hope your problem something as straightforward as this.

Andrew

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[aod]

It's just a thought but could it be that the anti syphon air brake hole has become clogged with salt? If it is the engine will syphon itself emply of coolant and then on start up it cannot generate enough suction to fill the system again. You can easily check it and it won't cost you a bean!

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