idle overheating prob

[shaenjay09]

i got an 87 3.0 mercruiser i/o with alpha 1. only when im in gear idling does it start to over heat. in neutral or any throttle its good. i changed the whole water pump, t-stat , checked risers, removed all hoses, nothings clogged. a buddy of mine said that the head gasket bolts might have loosened up alittle bit which lets the exhaust heat up the water at the low idle. and i did wide open throttle for the first time when it started. you think this might be right?

 

[Gary H NC]

Re: idle overheating prob

What water pump did you replace? The engine mounted circulation pump or the impeller in the drive?

 

[shaenjay09]

Re: idle overheating prob

What water pump did you replace? The engine mounted circulation pump or the impeller in the drive?

it only has the one in the lower unit

 

[Bifflefan]

Re: idle overheating prob

it only has the one in the lower unit

It also has one on the engine to circulate the water.

 

[fat fanny]

Re: idle overheating prob

It would be a good idea to test the circulation from the engine mounted water pump before proceeding any further, Also it's not a good idea to run a marine engine @WOT out of the water especially if water cirulation is @ question

 

[Bondo]

Re: idle overheating prob

a buddy of mine said that the head gasket bolts might have loosened up alittle bit which lets the exhaust heat up the water at the low idle. and i did wide open throttle for the first time when it started. you think this might be right?

Nope,....

I'd do a flow test from the drive, at the T-stat housing fitting 1st...

 

[littlebookworm]

Re: idle overheating prob

Were any pieces of rubber missing from the water pump impeller? If so, you need to find them; they may be blocking the cooling system. Most likely place would be in the power steering cooler. Remove it and back flush it. Check the exhaust flappers in the exhaust pipe. It/They may be bad, causing flow problems. Check the water circulation pump, as was suggested, at the front of the engine. And finally, check the exhaust manifold and riser system for rust. Hy