View Full Version : Engine overheating

the dog house
05-30-2010, 08:20 AM
I have a 1995 Marine Power 350 gas port motor that is overheating. I've tried the following items to fix the problem:

1. replaced impeller on raw water pump
2. checked heat exchanger for clogging - it was clear
3. replaced the water pump on engine
4. replaced the raisers
5. checked sensor on manifold with starboard motor - not the problem
6. replaced thermostat
7. cleaned strainer
8. cleaned intake strainer on bottom of the boat
9. checked flow of water through the oil and transmission cooler

The motor use to run at 180-185 at 3400 rpms. Now it climbs to 200 and shuts itself down. At an idle it runs cooler than my starboard motor, below 2000 rpm my motor runs at normal temperature.

Is there anything that I am missing at this time to check?

05-30-2010, 08:51 PM
Crud inside the block?

I would be doing Compression Checks to rule out a blown Cylinder Head Gasket, plus doing a CO test on the water within the engine to test it for Carbon Monoxide in the Coolant. This would indicate a leaking Gasket on the Combustion side, only occurring when the cylinder pressures are higher when the engine warms up.

Plus, something is causing the engine to shut down well below boiling point.


the dog house
05-31-2010, 07:26 AM
Thanks for the suggestion. I'll bring my compression tester next time I come to the boat. I keep the boat in the Florida Keys but I live up north orf the Keys.

I ran the boat yesterday for about 1.5 hours at 2800 rpms and the boat didn't get hot but again if I try to go at crusing speed it increases the temperature. I thought with that amount of time it would get hotter but it

Do you know of a second heat sensor on the block for engine temperature? I noticed they have it in my Owner's Manual but I can't find it on the engine? I found one off of the manifold.

Thank you for trying to help me figure out this problem.

06-14-2010, 08:11 PM
Other less likely causes:

Leaky strainer gasket. Worn raw water pump cam. Leaky raw water pump gasket. Sea cock valve partially closed. Collapsed hose section. Faulty heat exchanger cap. Low coolant level (if FWC).

06-16-2010, 05:41 PM
iam haveing same problem same engine done all you did . had the timeing set also was told to put a clear hose from cooler to riser to check to see if it has air bubbles in the water .got the hose today will put on tomorrow to check. have you found youre problem?