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Mariner 40 hp running hot

J

Jorho91

New member
Hi my mariner 40 hp (oil injected) 1989 is running a bit hot. I replaced the entire water pump assembly and it ran good for about a week now the tell tale water is steaming and too hot to touch. I took it apart last night to make sure everything was in order and all was well. What could be causing it to get to hot? I have a fishing tournament on the 17th so i have to get it fixed lol

Thanks
 
I took everything apart yesterday. Checked the water jacket gasket around the spark plugs and checked for any obstructions all was fine put a new powerhead gasket on as i tore the old one pulling it apart. Checked the water pump/impeller it wad all good. Checked the seal around the tube going into the power head all good. This is baffling me. Its spitting water just fine the water is just super hot.
 
There's two types of impellers out there, one of which is volume related (vs. pressure related). I had a late Merc 9.9 hp with the volume type impeller that I absolutely could not make to pump water (nor could the previous mechanic). Took apart everything in sight and eventually gave up on it.

I hope somebody else here has a suggestion that will help you.

Sorry.

Jeff
 
Thank you jeff i appreciate your input. Hopefully someone can help. Im going to tear it apart again tmrw and see uf i cant figure it out.
 
This a 2 or 4 cylinder???? If a 2 cylinder check the t-stat. If yours is 2 cylinder you have a volume impeller or if a 4 cylinder a pressure type.
 
Okay--that's the "easy" one to figure out.

You need to start with a bucket test of the LU. The photo below shows how to rig up a way to spin her over in a bucket. You should see a noticeable flow of water, even at low drill speed, and it should spray water strongly if you throttle it with your finger. If not, tear into it again.

Jeff
 
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