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Hi all -- We were running my 1974 13 Sport w/ a 1996 Yamaha C40 on Saturday. 3 guys and a surf board running through ocean surf to get through an inlet and then some island exploring for a couple of hours. On the way back, with WOT, the alarm would go off. We throttled back down and the alarm quit. We ran at maybe 3/4 throttle for a while with no issues. Throttled back up and the alarm started again, so we backd off until it stopped.

Any ideas what might be causing this? The pee water coming out of the engine was warm. Not hot, but warmer than the water we were running in. Was the engine overheating? What could be the cause?

One other thing that happened was when we started back up to go back to the marina, the engine kept cutting off when we threw it in to gear. Turnes out, the anchor line had wrapped around the prop. Once removed, the engine went in to gear fine. Did we damage something in the effort to put it in to gear with the prop bound by the rope that may be causing the alarm to go off? Just wondering if there's a connection...

Thanks!!!

Bruce

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Bruce, I cannot see how there would be a connection between your situation with the anchor line and overheating at WOT.

As far as the overheating goes, there are a lot of possibilities, from water pump or thermostat needing replacement to running lean. The configuration you were in (fairly heavily loaded, WOT) is the most prone to overheating - remember these motors are cooled by water and by the air / fuel mix passing through them, both of which are affected by RPM. Are you sure you a propped correctly? Overpropping would exacerbate this condition.

Tim

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Not sure if your Yamaha has this but on the Johnson/Evinrude engines there's a sensor in the fuel line just before the pump that measures vac and sets off the alarm if it gets too high, indicating a restriction in the fuel line. This usually happens at WOT when the draw is largest if there's any kind of restriction. So check the fuel line for a kink and also the tank vent to see if it was open fully. Given that the alarm stopped as soon as you throttled back, it doesn't sound like an overheat.

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Thanks for the help, gents. As far as the prop goes, Tom W. guided me through prop selection not too long ago. I went w/ a Yamaha 14 pitch based on the data we plugged in to the calculater he recommended and that's what we came up with. From others on this forum, that seems to be about right for a 13' w/ a 40hp hanging off the back. I know there are other factors that play in to prop selection, but I think a 14 pitch should be in the ballpark and not be the cause of overheating. But, who knows!

As for a possible kink in the line, that is indeed possible. We were stacked w/ "crap" including a 7'8" surf board :) so something pressing up and restricting the fuel line is certainly within reason.

The interesting thing (to me, anyway) is that the condition went away once we throttled down and ran her at 1/2 to 3/4 throttle. I'll see if it happens again next time I take her out -- but this time w/ less load!

All of that said, replacing the thermostat at season's end isn't a bad idea, either way.

Bruce