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'89 Sunsetter Thermostat


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Changing my thermostat...It won't fit into housing, Double checked part number three times. Ordered three different ones. None will fit. Everything on engine is original. 

1989, Ski Comp. Any advise to find the correct size?

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Thermostats are standardized dimensions for any particular brand.  Here are a few things to check:

1.  Verify base engine brand as I am not sure if Malibu was all GM in ‘88 so could be a Ford.

2. Verify specifically on a Mercruiser that you are correctly assembling the thermostat / spacer housing setup as that can be an issue.  Google Merc or Marinizer cooling system diagrams for reference.

3.  Make sure corrosion / gunk buildup etc isn’t the problem.

4. And don’t buy an automotive part as they corrode in raw water.  

Hope this helps.

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  • 2 weeks later...

Try this link:


My 1990 had thermostat housing design #2. Thermostat part # 805273 1 , also part # 8M0089715

Mercury Quicksilver Thermostat-140 8m0089715 is equivalent to parts:

18-3551 Sierra Marine

18-3551 Sierra Marine

508717 Evinrude Johnson OMC BRP

508619 Evinrude Johnson OMC BRP

508566 Evinrude Johnson OMC BRP

508562 Evinrude Johnson OMC BRP

807252Q4 Mercury Marine

807252Q 4 Mercury Marine

9-43013 Mallory Marine

9-43013 Mallory Marine

13030 GLM

13030 GLM

MC-29-59137 Barr Marine

MC-29-59137 Barr Marine

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