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I have a Mercruiser 228 with an Alpha drive. The engine seems to run a little bit hot. If I leave it sit idling (1000 RPM) for too long eventually the temp gauge will creep up near the 230 degree point. If I increase the throttle just a little bit up (160 RPM) it will be gin to cool down. When running it at higher speeds on open water there is never any kind of a problem. I have been told by several mechanics if the problem was the water pump it would gradually get worse but it does not. It has always done this for the 3 years I have owned the boat. The problem does not get any better or any worse, its always been the same. Is the thermostat or temp gauge defective, or the water pump after all?

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  • scott_jahnke Jul 08, 2010

    This opinion agrees with my own thinking, just wanted to bounce it off someone else.


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Actually, idling this mercruiser 228's engine is like idling a car. The traffic fan in a car will go on because heat builds up with the lower rpm's on the water pump. Also, less wind to cool a radiator.

I see that you noticed a difference between 1000 rpm and 1600 rpm where it cools down and at higher speeds you never have a problem.

If the water pump had a problem like a leak or poor circulation, then this would indicate that you have to replace it.

I don't think anything is defective, based on what you said.

In GM vehicles, for instance, temps rising to 230 or so are not uncommon. If you apply this to your question, I would say that you're on safe ground. Just avoid idling for long periods of time, just like a car.

Happy boating to you.

Posted on Jul 08, 2010

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