MerCruiser 350 Cooling question

[RoseMan806]

Here we go. I've got a 350 MerCruiser alpha one with the raw water pump in the drive and a raw water cooled system. This past season the raw water pump, manifolds, risers, circ pump, themostat + housing have been replaced. I have noticed that at idle the engine is running at 160*, the port manifold and riser are about 20* cooler than the starboard side. Port would be 80* and Stbd. would be about 100*. When up on plane, port runs at 105* and stbd runs 165* Has anyone run into a temp spread like this? I'm also not sure which temp is the correct one. I have checked the restrictor gaskets and they are installed correctly. Also when I pulled the risers off I noticed rust marks where water was and had been sitting in the exhaust side of both manifolds. Any help would be great.

 

[Don S]

Re: MerCruiser 350 Cooling question

Gonna need some engine Serial numbers, Years, thermostat housing types etc. There shouldn't be a 60? difference while on plane.

 

[RoseMan806]

Re: MerCruiser 350 Cooling question

This might be the correct serial number "OK024984" I'll have to come up with the other info later.

 

[mt375hp]

Re: MerCruiser 350 Cooling question

What would be the proper temp difference. or average temp. difference in the risers while up on plane?

 

[JustJason]

Re: MerCruiser 350 Cooling question

10 to 20 difference... but no more than 20. it's normal for 1 side to run a few degrees higher, but not 60.

 

[krisnowicki]

Re: MerCruiser 350 Cooling question

are you sure you were running at 105? how did you measure it? Also, how cold is the water you are in?

 

[RoseMan806]

Re: MerCruiser 350 Cooling question

are you sure you were running at 105? how did you measure it? Also, how cold is the water you are in?

I was using a infared temp gun. The temp of the water was roughly 70*.