4.3 merc running cool?

[ccyoder]

Hi all. Long time lurker, first time poster.

I recently purchased an 89 Glastron I/O with a 4.3L merc, 2 bbl, thunderbold ignition. It's freshwater cooled.

The boat runs great, but the water temp doesn't get much above 120, never higher than 140, even when cruising or near WOT. Is this too cold? The boat came with no manual and I haven't been able to find the normal operating temp by searching these forums or elsewhere. I seem to remember reading it should be around 175, but can't find that source again.

Will this cause problems/damage if engine continues to run cold?

By the way, the only other issue I've had, and believe to be unrelated, is that in about 15 hours of lake time, I've stalled twice going from gear to neutral. Suspect a sticky shift cable and will have that replaced.

Thanks!

 

[Don S]

Re: 4.3 merc running cool?

You probably need a new thermostat. It should start opening at 140?. The engines then run at 160 to 175?.
The engines run better at that temp than they do at 120.

 

[ccyoder]

Re: 4.3 merc running cool?

Thanks, Don!

 

[Magik]

Re: 4.3 merc running cool?

I have a similar issue. I replaced the thermostat and that didn't really do much (although average temps did raise slightly). I also checked the temp sender sensor and it was fine.

At least with mine I think that for some reason cold water is being circulated through the engine event when the engine is cold.

It could be clogged bypass passage in the thermostat housing causing cold water to be pumped into the engine and then its forcing the thermostat open on its way up or just too much water being pushed by the raw water pump in the first place and some goes through the bypass and the rest goes through the engine.

 

[180shabah]

Re: 4.3 merc running cool?

Magik - Start a new thread.