overheating

[operatetheboat]

I have a 1985 21 ft Sunrunner with a Volvo 225E 305 chevy 4bbl and a 175 volvo outdrive. I have owned the boat since new. My problem is that it started to over heat at high speed. As long as the boat is idlleing or moving slowly the temp stays down. I have determined that the raw water pump is picking up all the way through the transom. My problem is from the hose union down. I replaced the hose union and gasket. My next step is the guide sleeve. My question is how do I tell if the guide sleeve is bad???? The volvo dealer tells me they just replace the sleeve... Well that little sleeve is almost $600.00. If you replace it and it is still sucking air I have not solved the problem. Your suggestions appreciated ..

[Gilbert]

Have you determined for sure that there is an air leak?
If the ignition timing is wrong it can cause overheating.

[operatetheboat]

Know for sure that I have an air leak .... Its always afer the out drive comes above the water line on plane ... I have used a clear plastic connector to see the air bubbles going to the raw water pump.