4.3l engine overheating at idle.

Old 08-10-08, 03:24 PM
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4.3l engine overheating at idle.

I have a Regal medallion with a Mercruiser 4.3l engine and an alpha gen 1 outdrive. it was given to me by a co-worker. he told me that the engine over heats while idling, and that the Risers needed replacing. it doesn't make sense to me that the engine should overheat due to the risers. I got it started this weekend, and it does indeed get hot after idling (for quite a while I might add 15-20 mins) but give it some throttle, and it cools right down. does anyone have any ideas as to what the problem might be? could this be normal since the drive has a lower gear ratio, and thus not turning the waterpump in the outdrive fast enough to provide enough water to cool the engine at idle? I don't know the gear ratio of the outdrive. I do however, have another boat with a mercruiser 5.7l vortec v8, alpha gen 1 outdrive. no overheating issues at all. any ideas / help will be appreciated..

Thanks, Craig..
Old 08-10-08, 04:18 PM
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I'm not a boater, but my first thought would be to remove the water pump and make sure the impeller blades haven't corroded off.
Old 08-10-08, 04:22 PM
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The gear ratio of the transmission has nothing to do with the water pump, so that's not a likely cause.

The impeller in the fresh water pump could be compromised. Many techs recommend changing them every two years. They get damaged easily, even by running the engine for a little as 20 seconds with no water.

The impeller is nothing but rubber tines and friction.

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