Engine Running Hot

[IRS]

Have a 2004 4.3L Mercruiser. (not sure of the outdrive it is on the boatlift and is raining) The thermostat shows that is starts to run a little hot when running it a little harder( eventually the alarm goes off). But if I run it at quarter or half throttle, it does heat up a bit but alarm doesn't go off. People have told me that the easiest thing to change is the impeller. Also that junk (sand etc) can get jammed in there and will limit the water circulation. From what i have read it sounds pretty easy. But am looking for for more detailed instruction or suggestion. Also looking for a exploded drawings for assembly. That is what saved me with me sled's (snowmobile).

Thanks

 

[Don S]

Re: Engine Running Hot

Need to know what outdrive you have, Bravo or Alpha. The impellers are NOT the same, and are not even in the same place. The Bravo is on the engine, the Alpha is in the outdrive.
An engine SN would be VERY helpful.

 

[IRS]

Re: Engine Running Hot

yeah i figured that it stopped raining so went and checked.. It's an Alpha One....

 

[Don S]

Re: Engine Running Hot

Here is a link to the OEM service manual for your drive.
http://www-alt.mercurymarine.com/mnetdata/SERVICE/CRUISER/Servmanl/14/14cover.pdf

The thermostat shows that is starts to run a little hot when running it a little harder( eventually the alarm goes off)

I'm assuming when you said thermostat, you meant the gauge, since the thermostat will tell you nothing,
But with the alarm going off to, you do have a problem, and the FIRST place you check on an overheat problem on a boat is the impeller.
They can be damaged in so many ways, that time alone is no indication of a bad or good impeller.

 

[IRS]

Re: Engine Running Hot

Thanks.. I'll see what comes out of this