4.3 mercruiser should i change thermostat ?

[vernonbluewater]

Currently runs at 175 degrees , specs say it should be 160 degrees. Overheat alarm goes off when I slow from 30 to 5 mph but turns off when it goes a smidge under 175. Any special tips on changing the thermostat would be appreciated.

 

[Bt Doctur]

Re: 4.3 mercruiser should i change thermostat ?

When was the impeller serviced last?

 

[swcolorado]

Re: 4.3 mercruiser should i change thermostat ?

It's pretty straight forward. You will need a gasket. I generally like to spray the paper gasket with adhesive gasket coating (kind of a copper sticky spray).

You may want to use a wire brush to clean the mating surface. Pop it in and bolt it back up. Check for rubber impeller pieces in the hose ports while you're there.

 

[fossill]

Re: 4.3 mercruiser should i change thermostat ?

Absolutely no gasket spray on that thermostat gasket as per the merc manual if the gasket has bonding tabs on it.

 

[vernonbluewater]

Re: 4.3 mercruiser should i change thermostat ?

Bt Doctur - I have recently purchased boat so I don't know if or when impeller has been serviced. Any advice on this greatly appreciated.

 

[extreme76]

Re: 4.3 mercruiser should i change thermostat ?

I suspect the impeller also, not the thermostat. My 98 4.3l has a 160 degree thermostat and normally runs up to 170 on my gauge maybe a little higher when run hard in warm water. I believe that it is normal to run a little above the thermostat temperature, I am assuming yours is rated for a 160 degree thermostat. It could be your thermostat not opening quite all the way, but the temperature alarm going off when slowing screams impeller to me. When you slow down it isn't supplying enough water flow. I would change that before I did anything else.