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I have a 2002 Vmax 250 OX66 on a 26' Playcraft triple tube pontoon boat. Last week when I took off down the lake the overheat alarm went off after about 5-10 minutes of cruising at around 4000-4200 rpms. I shut it down for a few minutes and made sure nothing was clogging the inlets and took off again. Closely watching the water pressure guage I noticed that it was fine (anywhere from 12-20 psi at 3000-3600 rpm), but when I would open it up a little (over 4000-4200 or so) the pressure would start to drop - all the way down to 5psi or lower. If I slowed down again, the pressure would go back up again to normal. The water stream was good and steady coming out of the engine.
I spoke to a mechanic at the lake who said it was probably the impeller in the water pump. Had it replaced and went out the next day with the same problem. When I got the boat home, my local Yamaha mechanic talked to the people at Yamaha who were almost certain it was the poppet valve. He removed it, cleaned it and flushed the system real good. I had the boat on the lake yesterday and the same problem persists. We bought this boat used last September with 66 hours on this engine, and it has been great up until this point. Engine has around 83 hours on it now. Any suggestions would be great. Thanks!
I spoke to a mechanic at the lake who said it was probably the impeller in the water pump. Had it replaced and went out the next day with the same problem. When I got the boat home, my local Yamaha mechanic talked to the people at Yamaha who were almost certain it was the poppet valve. He removed it, cleaned it and flushed the system real good. I had the boat on the lake yesterday and the same problem persists. We bought this boat used last September with 66 hours on this engine, and it has been great up until this point. Engine has around 83 hours on it now. Any suggestions would be great. Thanks!
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