4.3L mercruiser overheatig; starboard manifold hot

LoriJohn

Cadet
Joined
Jul 24, 2011
Messages
9
2001 4.3L mercruiser temperature intermittent alarm, moslty at higher rpms. Replaced impeller in foot last week. Replace thermostat last season. Noticed Starboard manifold hot and thermostat and port side manifold cool. Removed and cleaned manifold and elbow. Cleared some metal, and all water channels are clear. Starboard side still hot. Should one side be hotter than the other? I'm thinking about running test without thermostat to see if thermostat is not feeding water to starboard sie. Any ideas? Thanks.
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: 4.3L mercruiser overheatig; starboard manifold hot

If the manifolds and elbows are plugged up, you replace them, not clean them out.
They are plugged up with rust from inside the manifolds and elbows and getting hot is a warning.
If you just clean them, the next thing you get is water in the engine and if salt water, probably you will need a new motor.
 

LoriJohn

Cadet
Joined
Jul 24, 2011
Messages
9
Re: 4.3L mercruiser overheatig; starboard manifold hot

Thanks, but I don't know that they were actually plugged up. There doesn't appear to be any change in temperature since I "cleaned" them.

Just did a water test. Looking at temp gage, the thermostat is obviously doing something because it gets up to 175/180 degrees then drops back down to about 170. Warning horn goes off and on as that happens.
Also, noticed during fresh water flush more water coming out of starboard side than port. Should that mean anything to me?
 

Dshow

Petty Officer 1st Class
Joined
Jan 1, 2007
Messages
313
Re: 4.3L mercruiser overheatig; starboard manifold hot

That's been an age old discussion regarding the starboard exhaust manifold getting hotter than the port... From the thermostat, it feeds both the manifolds. With some adapters, connect the port manifold to the starboard thermostat output and starboard manifold to the port thermostat output. If the issue changes sides, you know it's the thermostat output.

The temperatures you mention don't seem that hot to me...
 
Top