94 OMC/Volvo Engine over heats when first launched

[janpoe]

I have a 1994 OMC/Volvo 351 Ford. When I first launch the boat it overheats to 220-230. I can usually get it to
go down by reving the engine, turning it off a number of times, reving, etc. Last weekend it took a long time to get it to
come down to normal. Once it does come down it will run 120-140 all day long...no problem. The impeller
has been replaced twice recently. It as if the cooling system is taking too long to prime. I have not checked the thermostat yet but plan on it but again, once the temp comes down it stays down. Is the impleller driven by the engine the only one or is there one in the out drive? I know there is one in the water pump and another driven by the drive belts. Also the lower unit was replaced last year but I had this problem before and after.

 

[Don S]

Re: 94 OMC/Volvo Engine over heats when first launched

Post a picture of your drive. In 94 there was a possibility of about 4 different drives that could be on that engine.

 

[janpoe]

Re: 94 OMC/Volvo Engine over heats when first launched

 

[talon8]

Re: 94 OMC/Volvo Engine over heats when first launched

That is an SX cobra drive so you have an engine mounted water pump. I'd look for an air leak in the pump suction hose. If it is sucking air, the pump is having a hard time priming.

 

[janpoe]

Re: 94 OMC/Volvo Engine over heats when first launched

That is an SX cobra drive so you have an engine mounted water pump. I'd look for an air leak in the pump suction hose. If it is sucking air, the pump is having a hard time priming.

So I pulled out the thermastat and ran the boat out of the water with rabbit ears. Water was going but not coimng out. Eventually the motor started to over heat. i turned it off and went in the house for awhile. went back out, started up
ran it for a few more minutes, water on but none coming out. Then all of a sudden like something opened up, water started flowinf out of the out drive and the temp came down, took out to the lake and was fine the rest of the day, alomost as if there is another thermastat in there somewhere sticking and finnally opens....baffeling...