Cooling System Ford Commander Engine

I have a 1978 CorrectCraft Ski-Tique with a 302 Ford Commander Engine and have experienced an over heating problem during the past two boating seasons.
I have replaced the impeller in the original water pump system. The problem still exists. I have also replaced the original water pump with a new brass water pump that was recommended by a CorrectCraft parts dealer. This still did not correct the problem of over heating. I have replaced the thermostat with a thermostat I obtained from a CorrectCraft parts dealer. The over heating problem still exist. Water appears to be coming out of the exaust pipes in equal quantity during testing.
Does any one have any suggestions that might correct the problem.
Thank You
momanmo

HOT HOT?

old engines get chunks of scale ( and old chunks of rubber ) into the cooling passages.

start simple and remove the tranny (and engine) oil coolers. free from obstruction? you would be amazed at the crap you'll find in there. i could make a fake xmas tree with all the pine needles, bark and sticks in the pre-strainer days.

most thermostats are made by robertshaw here in knoxville. if the work once thay are boxed and out the door. on the cars , i buy three and fire up the stove. whichever one opens first is installed and the other two are returned. take yours out and check it on the stove with thermometer. new does not equal good in thermostat land.

you could be sucking air into the cooling system from an frayed internally hose end (or a bad o-ring if you have a strainer.)

replace the two one inch hoses from the upper thermostat to the manifolds with some clear tubing. if you see air, you either have a air leak, bad head gasket or a crack in a casting. simple test.

does it run cool on the hose at the house and overheat at the lake?

take a look at you plugs. a lean condition will cause overheating also. clogged fuel fiter or carb, bad base gasket ect.


edit....damn FORDS...........

if it overheats connected to the hose and fails the air bubble test, do a compression check. it may or may not show anything.

pull the heads and change the head gasket. fel-pro MARINE gasket sets are available at your local auto parts. i can look up the number if i cam find my book.)

bills right, the head bolts on a sbf don't have much to bite onto the deck.

It's probably blowing on the exhaust side, if it was a closed water system it would be blowing back up the radiator with the cap off. Lean ,junk etc are alway's possibilites. However head gaaskets are you best bet. Lean conditions, too much timming etc would show more under a load such as running in the water. Have changed tons of them, my opinion, good luck.