View Full Version : 1991 4.3 L Mercruiser problems

07-07-2010, 10:44 PM
I have a 1991 BlueWater with a 4.3 L mercruiser motor in it. Recently I have noticed the smell of antifreeze when I turn over the motor. It also has been missing once in a while when I am over 3000rpm. No leaks in the hoses but am wondering if this is a sign of leaking head gaskets. The temp gauge has also be jumping all over the place. Any suuggestions?

07-08-2010, 12:28 PM
The antifreeze pressure cap could be weak. Pressure test it at an autoparts store or just replace it. You can also pressure test the cooling system and watch for a leak. Pour some antifreeze dye into the system and search for the leak w/a black light. Look under the circulating pump w/a mirror. There is a weep hole to allow fluid to seep out when the bearing seals are worn.

Pull the spark plugs and read the color of the electrodes. You should see tan to medium brown color. Any other color means there is a problem; i.e., bad plug wire, worn dist. cap, bad plug. The plug will be clean looking if there is antifreeze seeping into the system.

Peter Maile
07-08-2010, 05:21 PM
the last post was good advice,

after doing all that, if it still "smells" and the temp gauge jumps all over still.

My question is does the temp go up "and jump all over" when under load:

While you are under way @ part to full throttle?

If so it is more than likely a head gasket.

I hope this helped.