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post #1 of Old 07-23-2008 Thread Starter
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Yanmar 2QM15 raw water pump problem

Hi, I am new member and I have learned something good from SailNet member: put the starting key into the raw water intake valve.... yes if I can remember to put it there.
My boat is 1980 Spencer 34 Sloop, flat bottom U shape hull and the engine is forward under the V berth,because of this the raw water intake was only about 16 inch below water line. The Yanmar 2QM15 (raw water cool ) has about 2300 hours since new. She sailed beautiful and the engine run faultlessly in any sea conditions for over 27 years until this summer. In the pass few years the raw water pump has been dripping water from the pump shaft seal, so last winter I replaced the seal and put in new impeller put in good grease to lubricate but notice the housing wall and the cover plate were worn. This spring I took her out sailing in Gulf Island for about a week, had a good sailing in strong breeze and the sea was choppy but not really disturbed and the engine run smooth no problem. Under the engine was dry no more water dripping. This Summer I sailed up to Desolation Sound for about 4 weeks, used the engine often when calm no problem. On the way back, very strong Northwest wind was blowing 26 kt behind me running with jib only (engine not run) doing well over 6 knot, 3 foot sea from behind white caps all over the boat get toasted around. When arrived at the entrance of Pender Harbor, drop sail start the engine and within minutes the temperature alarm went off. Shut the engine off, rehoist the jib and sailed into the Harbor good thing the wind blow right into the harbor. After drop anchor, inspect the intake water filter no water in it, released the top screw air came out, water came in to the filter disconnect the hose to the water pump, water came out of the hose, water dripping out from the pump (from the engine). inspect the impeller looks OK Put the system back in, did few minutes of hand cranked (decompress the engine) to make sure the water pumped into the engine and start the engine runs OK water came out of the exhaust. Next day flat calm motor all the way to Gulf Island all day no problem. Sailing and motoring for several days in Gulf Island no problem. On the way back to home port (up in Fraser river in Landner BC) motor to Pollier Pass ( inside was flat calm, 16 kt NW wind out side in Georgia strait) 70 minute after slack water, flood water was about 4knot. The tide rip out side was big 3 foot waves white caps all over had the mainsail up. As soon the boat bouncing up and down the water temperature alarm went off . Shut the engine off and sail with main only, tried to hoist the genoa but the halyard got wrapped in to the top spreader took a while to get it off and hoist the gene and sail on up to the middle of the strait before the wind died. The sea still had the NW swell and boat was still bouncing some what but no more white caps.Went down to the engine room and bleed the water intake system (I became expert by then) started the engine everything was OK motor to Sand Head and all the way to Captainís Cove Marine in Ladner no Problem. I took out all the intake hoses and inspect, found no damage no soft spot no kink all the clamps are OK.
What I think was these:
The water pump was no longer self priming (the ability to create limited vacuum in the hose of about 4-5 ft length to pump the air out so water could get in) because of worn housing and cover plate, but as long as water in the intake hose and no air in it, it will pump the water.
With only about 16 inches deep from the sea surface, the water in that layer of sea was very well air rated especially in choppy confused sea. That is how the air got in even the water intake was not exposed above the water line (as all builder claim).
Yanmar does not sell the pump housing only the complete pump for $800 CAD. and have to order form Chicago.
I intend to replace with other make pump of similar size or even electric pump.
Before replaced the bad shaft seal and the water was dripping, probably it act as air bleeder, that was why I had no air lock problem before. So I intend to build air breathing system with a little tank for experiment until I found water pump replacement (not the :confused:$800 one).
Any comments and suggestions and advice from all member are welcome and appreciate.
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