Mercruiser Normal Running Temp

[FreeBeeTony]

I rebuilt a '67 Mercruiser 160. It seemed to be running hot. I removed the thermostst and it ran cooler but still looked like it would go past 200 if ran towards WOT for too long. After a few short outings it is running much cooler. Now at sustained high RPM's it is running at ~ 150 deg. While ideling through no wake zones its barely 120 deg. I think I must have had some kind of restriction in the manifold and passed it. The engine sat for a few years before I bought and rebuilt it. My question is this: Is it a problem running too cool? It is raw (salt) water cooled, I heard that the salt does more (quicker)damage to engines running on the hot side. I trailer and flush after each outing. So, should I put the thermostat back in or leave it out?

 

[FreeBeeTony]

Re: Mercruiser Normal Running Temp

bump

 

[snapperbait]

Re: Mercruiser Normal Running Temp

Yes to putting the thermostat in... <br /><br />Probably the reason it was heating up on you was because there was some trapped air in the cooling system..<br /><br />Just guessing here, 160 or lower degree thermostat..

 

[magster65]

Re: Mercruiser Normal Running Temp

My Merc. manual recommends a 140 thermosthat for RWC engines. FWC can run 160 and up.

 

[TedCT]

Re: Mercruiser Normal Running Temp

140 degree thermostat for raw water engines. Also, I read that not having a thermostat causes uneven heating and cooling which is not good for the engine.