overheating on Tri Cabin engine

[dmatz]

My boat has 350 mercruisers with a MC552-SB-C or GLM13230 thermostat housing. It has a 140 thermostat but has been running at 180. It recently started to peg the temp gauge. I checked the sea pump it is ok. The water pump is only a couple of years old. I replaced the thermostat with another 140 stat. During troubleshooting I discovered that according to the pictures I have of this thermostat housing I have a couple of parts missing or different. Missing is the U shaped bracket. and the cover gasket does not have a hole in the tab like the picture. Also pictured is a gasket with holes in the ears and 2 brass?? small holes on each side, everything else is there.
http://bpi.ebasicpower.com/c/MER8B/Ther ... Mercruiser
I also discovered that the block is where the heat is and the manifolds are relatively cool 155 compared to the block. 260 This leads me to believe it may be the water pump but I wanted to find out about the thermostat and housing before I change the water pump since it is fairly new.

[rickalan35]

Geez Dave, I sure can't help you out. My Tricabin runs at about 110 degrees.

Three years ago I overheated both engines after going thru a badly weeded area and subsequently fouled both intakes. As long as I limped along at idle the temp stayed down but if I increased the rpms even a little both engines heated up.

To my horror, our trusted mechanic disconnected the intakes and gouged them out while the boat was sitting in 30 feet of water. As she was sinking (in my opinion) he calmly and successfully removed the plant life and reconnected the rubber hoses. "you're as good as new, Mate," said he.

Good luck with those thermostats.

Rick