'97 Merc 5.7LX...140 vs 160 Thermostat??

[Have Fun Today]

Does it hurt to replace a 140 degree thermostat with a 160 degree thermostat? Which one is required by Mercruiser?

I have a 1997 Mercruiser 5.7LX with Alpha One drive. I thought the OEM manual called for a 140 degree thermostat but my Merc repair mechanic put in a 160 degree thermostat. To be honest, I don't remember how hot the engine ran on the old thermostat when it was working, never paid that much attention to it. The repair man, who is quite experienced and practically lives in his repair shop, said to use the 160 degree thermostat. The boat runs great now, temperature climbs to 170 before thermostat opens, then it operates right around 160.

 

[Don S]

Re: '97 Merc 5.7LX...140 vs 160 Thermostat??

The 160? stat is the one that should be in your engine.
It will start opening at 160? and usually the engines run at 175? under load.

 

[Searay260cc]

Re: '97 Merc 5.7LX...140 vs 160 Thermostat??

This thread is old but im having the same issue. West marine said to put a 140 on my merc 454. I have an 89 searay 260. The mechanic has been doing this for a very long time and he said to put a 160.

But is there is difference in length between those two. When he put the 160 in, there seems to be a space on the top so there must be something missing in there that will hold the thermostat down and press it firmly once the cover is put on?

Do i have a sleeve missing? Or does it need a thicker o-ring?