overheating 1997 3.0L volvo GS SX drive

In Feb. I bought a 97 chris craft with an over heat problem. I have changed the impeller and thermostat, I have also resealed the lower gear case. With the thermostat removed the motor stays cool at idle, but heats up immediately under load. With the thermostat installed the boat heats up instantly. When running with the muffs on the motor stays cool. The boat has only been in fresh water. The previous owner had an old impeller that he replaced that had no fins left.

What would be the next step in detrmining the problem? Is there an easy way to know if the manifold is blocked? Could it be a blown head gasket?

Thanks for taking the time to read my thread. Any advice would be greatly appreciated.

Re: overheating 1997 3.0L volvo GS SX drive

The old FINS may be stuck in the cooler or cooling system did you look for them?

Re: overheating 1997 3.0L volvo GS SX drive

The best I know how. I removed all of the hoses and could not find any debris.

Re: overheating 1997 3.0L volvo GS SX drive

Might want to read this.

http://www.4shared.com/account/file..._Overheat_Diagnosis.html?sId=oBu9Z92igYIAkW4F