Possible Overheating Problem?

[blupeblupe321]

Hi! I recently purchased a 1967 Cal 34 sailboat with an atomic 4 gasoline engine. I am new to this particular motor and noticed when I bought it the previous owner was using vice grips to adjust water flow from the water pump to the thermostat. I noticed when I remove them no water comes out of the exhaust but when I clamp them down water comes out pretty consistently. I have been having some problems with the motor overheating (or so I think). The motor starts up fine when cold but after running for about 5-10 minutes the temperature gauge will go to 240 degrees and the motor will shut off instantly. It’s not a gradual shut off and it doesn’t make any noises before it happens it just cuts off almost like its a electronic safety switch that prevents the motor from overheating. After cooling for about 15-20 minutes it starts up again no problem and the cycle repeats itself. I have checked all of my inlet and exhaust hoses for buildup and they are all clear. I also removed the thermostat and it was clean inside. Something makes me think that the motor might not be overheating at all because I measured the temperature of the engine block with an IR thermometer and it never got above 160 degrees. I suspect the temperature gauge may be faulty. Would a bad thermostat cause this problem? I know Moyer Marine sells an improved thermostat for the atomic 4 motor. Thanks!

[Al Schober]

Hello Blu,
Welcome to the forum. The place to come to for Atomic 4 advice - you'll have to decide whether it's good or bad.
With your temperature spiking like you describe, you have an overheat issue. A few things to try. First, remove the thermostat - let water flow through the block. Remember, the thermostat studs are also head bolts and need to be torqued. Second, put the vise grips back on the bypass hose - force the water through the block. Finally, remove the output elbow from the manifold and make sure things are clear there - that's a classic place for a blockage.
Let us know how you make out.

[CajunSpike]

Finally, remove the output elbow from the manifold and make sure things are clear there - that's a classic place for a blockage.
Let us know how you make out.

This is my vote to try.

[ndutton]

Early or late model engine? Is there a dome shaped housing integral with the head? Have a look at the drawings in this post and tell us which applies to you.

[roadnsky]

Something makes me think that the motor might not be overheating at all because I measured the temperature of the engine block with an IR thermometer and it never got above 160 degrees. I suspect the temperature gauge may be faulty.

Welcome to the forum!
I agree. IF the IR showed the block never got above 160° then you're not overheating.

It’s not a gradual shut off and it doesn’t make any noises before it happens it just cuts off almost like its a electronic safety switch...

Do you have EI or points?