454 Merc Thermostat

[Searay260cc]

My 89 searay had a 454 Merc. It seems like it take a 142 degree thermostat. The mechanic put a 160 degrees thermostat in it. Does it matter which one it is?

- Is there a difference in length between a 140 degrees thermostat and a 160?

-When he put the 160, he put the o-ring first then the thermostat sits on top but there is a space between the top of the thermostat and the cover. Should the cover have metal piece that would hold down the thermostat or

-The 140 degrees thermostat has a higher top that goes right against the cover?

- Do I need a sleeve that sits on top of the thermostat and when i put hte cover ,it secures the thermostat firmly in place?

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[joncrisler]

Re: 454 Merc Thermostat

You need to put in a 143 degree thermostat if you have a open cooling system. The spacers etc should go in as designed or you might get odd cooling behavior, like too-warm exhaust manifolds. There are a number of websites that have microfiche of the proper setup and parts.