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Thread: Water Pump YSM Help!

  1. #1
    Contributing Member II
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    Water Pump YSM Help!

    Hi, I just started the engine and it seems that the water pump in my YSM-8 Yanmar is not working. Does anyone know how does the pulley comes apart from the rotating pin that spins the impeller?
    I have the manual but is not very clear on how the pump comes apart and I can't figure it out.
    I think the seal around the pin has broken and its sucking in air. it has no suction power.
    Any help is GREATLY appreciated.!
    Thanks

  2. #2
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    Dear Stugy, Before tearing into your water pump, you might want to consider something I've done on several boat engines. They were all Yanmars but I suspect the same would apply regardless of maker. Find the highest cooling hose on the engine and remove the hose clamp from the end farthest from the pump. I'm looking at a photo of a YSM8 and I'd say it'd be the hose on the left, directly above the oil fill cap. Anyway, remove the clamp from the back of the hose (near twhat apears to be the bell housing), hold it in the vertical position and pour as much water in there as it takes to fill it up. Plug the end of the hose with your thumb and in one quick move, replace it and tighten down the clamp. Now start your engine and hang your head over the side to see if exhaust cooling water begins to flow. I'll bet it does. One clue that you're on the right track is that you have to pour a lot of water in there, possibly up to a quart. You might simply have an air lock preventing water from circulating. Sometimes this comes as a result of shutting the engine off when it's very, very hot, if the engine has sat unstarted for some time or if you're trying to start it just after recommissioning it after a winterization. Anyway, doing that is a lot easier than pulling the pump apart only to find out that it's just fine in there. Good luck, Glyn

  3. #3
    Contributing Member II
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    Question: Where does the suction come from? the engine or the water pump itself? I will try to fill that hose with water, you are right I had taken the hose off to replace the impeller probaly air in the system now.

  4. #4
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    Dear Stugy, The pump does the pulling (suction) but needs water on both sides in order to start moving water through it. Glyn

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