Mercruiser 454 Overheating after 1 -2 hours~

[illinoisbigwheel]

I have a 1990 Baja twin 454's. 1 motor is overheating. It has a new seapump, water pump, thermostat & temp gage.

The motor runs about 180 degrees for about an hour and half. When speed up, the temp climbs. The motor kind of "bogs down" then temp gage shoots to 220 degrees. This past weekend we were able to run almost 2 hours until we had a problem.

The other motor runs just fine!

Any suggestions as to what might be going on with this motor....I am stumped!

Thanks for all suggestions!

 

[maxxman04]

Re: Mercruiser 454 Overheating after 1 -2 hours~

bad thermostat, water pump. are engines injected or carbed?

 

[illinoisbigwheel]

Re: Mercruiser 454 Overheating after 1 -2 hours~

I've replaced the thermostat two times, but it continues to overheat. It is carb.

 

[maxxman04]

Re: Mercruiser 454 Overheating after 1 -2 hours~

check impeller in that motors outdrive. also, you may want to pull the plugs and note each ones condition, check to see if they all look the same. there is a slight chance you may have a head gasket problem.

 

[flargin]

Re: Mercruiser 454 Overheating after 1 -2 hours~

Pull off the water line connecting the in-side to the oil/PS cooler. check for pieces of old impeller in the cooler, jammed there.

impeller parts do not make it out...

 

[gaiter]

Re: Mercruiser 454 Overheating after 1 -2 hours~

Curious as to the outcome of this problem, my boat did the same thing to me today - ran fine until I cornered it for a bit, then sounded the alarm and spiked up to 220 degrees. Once I came down off plane, the temp went almost immediately back to normal around 170, but the engine would not run for about 10 minutes or so. Then started up and putted home with no issues. Any comments are appreciated. BTW motor is a 99 7.4L MPI.