Uneven Heat on Manifolds/Risers

[polpaul]

After launch this spring, I noticed that the starboard manifold and riser are getting more hot than the port side. The heat is not so bad that I can't hold my hand on them, but the one side is considerably hotter. (The engine runs at normal temp.) I removed the risers and there was no obstruction or rust in the water jackets. I then removed the water hoses leading from the thermostat, and they likewise seem fine (unobstructed). The water goes straight from the thermostat to the manifolds, so it would seem to me that this could only be an obstuction (which it doesn't appear to be) or the one side is somehow producing more heat than the other. Is this possible? What else should I look at? I have a 1997 raw water cooled Merc 5.7 (carb), Alpha One outdrive. Thanks.

 

[magster65]

Re: Uneven Heat on Manifolds/Risers

The heat must be coming from the head then. Check to see that your carb. isn't leaning out one side.

 

[polpaul]

Re: Uneven Heat on Manifolds/Risers

Thanks for the reply. I'll check out the carb. Also, if it could be that, could it also be a cylinder not firing?

 

[anesthes]

Re: Uneven Heat on Manifolds/Risers

Remember:<br /><br />If the starboard side is running lean, its the port side of the carb. Most intakes are cross-flow.<br /><br />-- Joe

 

[polpaul]

Re: Uneven Heat on Manifolds/Risers

Thanks! Actually, I didn't know that.

 

[jlshields]

Re: Uneven Heat on Manifolds/Risers

polpaul, if you have a 4 bbl you have a dual plane intake manifold, not sure about 2 bbl. Cyls. 1, 4, 6, & 7 feed from one side of the carb and 2, 3, 5, & 8 feed from the other. Also on the Alpha you have a cold water bypass that dumps excess cool water to the port exhaust elbow causing it to run cooler. My '97 5.7LX B3 manifolds don't run the same temp either. john