Old 07-17-03, 11:22 AM
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Unhappy overheating

I have a 77 Searay 220 with an MLM228 I/O CI. When in the water at idle it runs at 150 degrees up to 10 mph but when you get it up to 20 mph the temperature starts to rise slowly and at 34 mph it climbs to 210 degrees. I can drive it about 2 miles before it over-heats. I have pulled the exchangers and cleaned them out real good and checked the water pump on the engine and it's okay. It had a new impeller installed two years ago. The compression reads facing engine left bank 8-145, 6-142, 4-137-1/2, 2-145, right 7-147-1/2, 5-130, 3-155, 1-152. I squirted oil in #5 and rechecked and the reading went up to 135. Can you explain or give me any ideas as to why the temperature keeps rising?

Old 07-18-03, 07:52 AM
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Hello Bob. Welcome to the web site and the boating forum.

Random thoughts:

Has the thermostat been checked or replaced? It may not be opening fully.

Also check the warm water exist points. Possbile restrictions in those location as well as the intake area.

Lean fuel mixture and or engine timing at speeds off idle may be part of the problem.

I haven't covered all of the potential possibilities. The forums resident boat repair professionals will have additional helpful information, suggestions and advice. Check back on your question several times for additional replies.

Check back on your question several times over the next few days for additional replies.

Regards, Good Luck & Safe Boating.
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Old 07-28-03, 08:09 AM
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The impeller should be changed annually, and i also feel
that the thermostat and/or housing may be your problem.
The manifolds can look ok but really be clogged. When you
accelerate do the supply hoses get stiff, overpressurized?
If so the you have clogged manifolds. Generally speaking,
we replace manifolds after 4 to 5 years of service.
Yours could also be a peice of old impeller stuck in the waterway
from the drive to the engine.
A very close examination of the entire cooling system is
needed to preserve an othewise sound engine.
I like the compressions! good engine.

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