over heating issue

[billy boater]

Hello all ok so here is my problem. I have a 85 (I think) mariner 25 horse and it will over heat after the motor has been running for about a half hour or so. if i take it to the lake and fire it up it runs fine and has a good streem of water coming outa the pee hole. Then after about a half hour or so putting along or wot it will loose power and start spitting steam out of the pee hole after the motor cools off it will re start and pee water just fine. I have replaced the impeller and housing,t stat, checked compression and it was about 130 in both cylinders. Not sure what else to look for any tips would be greatly appreciated thanks in advance

 

[mercfixer]

Re: over heating issue

Sounds like a restriction in the water tube from the water pump to the power head. The corrode and clog over time and some even corrode nearly shut at the top of the tube under the powerhead.

 

[latin monkey]

Re: over heating issue

also check the water lines and fittings as they will also get corroded

 

[billy boater]

Re: over heating issue

Ok i will check that out. But if it was cloged would it still run fine with a good stream then as it gets hot start to shut down?? I just ran it in the drive way for a good half hour in a tub of water and it didnt miss a beat. I had good water flow coming out the weep hole. I even pulled the t stat out and ran it to make sure there was good water coming out and there was. I have a temp gun and the whole time it was running i was checking all over the motor to see if there were any really hot spots and the hottest spot on the entire motor was 165. So im thinking my issue is deffinetly under load.

 

[75TowerOfPower]

Re: over heating issue

Its completely different under load, just like driving normal versus towing your boat. The need for more power increases the heat. So you also may have a piece of something thats constricting the flow and only happens when you are under load since the pressure is increased.