'85 OMC engine overheating after 30 or 40 minutes of idle speeds

[jakesgrace]

I recently bought an '85 wellcraft boat. It has a 5.7L engine and seems to run well with the exception of the engine getting hot after about 30 or 40 minutes of idle speeds. I was thinking that it might be the thermostat but I am new to this arena and am seeking help. The boat was just summerized by a local shop and I've had it in the water twice but only at idle speeds. (The closest lake to me is a no-wake lake.) Are there any tests I can do at home with water muffs? If it is the thermostat, is it something I can do? If its an impeller issue is it something I can do? Is this characteristic of OMC's? Any help would be great!! Thanks.

 

[Don S]

Re: '85 OMC engine overheating after 30 or 40 minutes of idle speeds

The FIRST thing you check on any marine engine overheat problem is the raw water pump impeller.
Doesn't matter if it's OMC, Merc, Volvo, or you name it.

 

[jakesgrace]

Re: '85 OMC engine overheating after 30 or 40 minutes of idle speeds

Thank you for your advise. I made an appt. to have that checked/replaced in a week or so. Thanks again!

 

[KaGee]

Re: '85 OMC engine overheating after 30 or 40 minutes of idle speeds

I believe you have a "Stringer" drive. With muffs hooked up and the drive ALL the way down, you can do 2 simple tests:

1) look for the "pee" stream coming from the intermediate housing shooting a good stream to the ball gears.

2) Loosen the hose on the thermostat housing coming from the drive and inspect the water stream. You should be able to fill a 2 gallon bucket fairly quick.

If those two tests pass, then you possibly have a bad thermostat or restriction in the system from corrosion build up.