One side of motor runs hot

H

Hugh H

Cadet
Joined
Jul 20, 2008
Messages
29
98 MerCruiser v-6 carb. alpha drive. riser on one side of engine gets hot to the touch and the other cool. I'm running it out of the water and can see the cool side of the engine has much better water flow out. Moved the trailer and the situation has reversed. Circulation pump is not leaking ( so it's good? ) Thinking my water P/U impeller isn't moving as much water as it should. Thanks for your help.

Hugh
 
bomar76

bomar76

Lieutenant Commander
Joined
Jun 27, 2002
Messages
1,963
Re: One side of motor runs hot

What you see coming out of the idle relief ports is meaningless. You saw that for yourself when you repositioned boat.
One side normally runs hotter than the other, just the way they work, but unless you actually shoot it with an IR gun it's just subjective on how much hotter one side is than the other.
A partially blocker riser or mainfold can do that, but before I threw parts at it I would actually measure the difference.
 
H

Hugh H

Cadet
Joined
Jul 20, 2008
Messages
29
Re: One side of motor runs hot

There is a direct correlation between the volume of water coming out of the idle relief ports and the temp. of that side of the engine.( as in ouch!!! don't touch and the other side i'll hold this all day) I'm thinking if it was a blockage it wouldn't bounce from one side of the engine to the other. In moving the trailer it seems to be a gravity thing as to which side the water exits. Boat/trailer not level.
I boat in fresh and salt, and always flush motor coming out of salt. Almost always :)

Thanks
 
bomar76

bomar76

Lieutenant Commander
Joined
Jun 27, 2002
Messages
1,963
Re: One side of motor runs hot

Answer:
Don't boat in unlevel water.
 
achris

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: One side of motor runs hot

As soon as you put the boat in the water and run it all will be back to normal.... What you are seeing is nature taking the 'path of less resistance'. Completely normal and nothing to be concerned about... Yes, an exhaust elbow with little water flow will get hot, very hot... As Bomar said, find a level lake. :D

Chris.....
 
tkrfxr

tkrfxr

Petty Officer 1st Class
Joined
Nov 10, 2009
Messages
313
Re: One side of motor runs hot

Check the water flow through each manifold and riser. I noticed one out of four of my risers was hotter than usual last season. I then noticed rust bleeding through the joint...I could not leave it alone... I had to take them apart and found all kinds of rust flakes, Neutra-Salt residue and had to do a cleaning job, like a chimney sweeper....

I ran the engines a few days ago and now all four risers feel the same warmth....here are the pics...

http://forums.iboats.com/showthread.php?t=381272
 
H

Hugh H

Cadet
Joined
Jul 20, 2008
Messages
29
Re: One side of motor runs hot

I suppose i'll just run it and see what happens. 10th year with this boat first time seeing/noticing this condition. Thanks for your time and thoughts. Bomar i've never seen unlevel water.
 
bruceb58

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,478
Re: One side of motor runs hot

If you run in salt water, one of your risers could be clogged more than the other. The difference in temp should be no more than 20 degrees if you measure with an IR meter.
 
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