Fired up my 7.4 MPI today for the first time after a total tear down. Runs great, gets right to operating temperature on the hose and stay there. Only issue is that the starboard side exhaust riser gets substantially hotter than the port side. The water flow from the through hull is equal. I checked the riser hose, not clogged. Took off the thermostat housing no clogs there good equal water flow. It has new Head gaskets, raw water impeller, thermostat, exhaust manifolds and the risers were replaced last year. I'm kinda at a loss at what it could be. Tomorrow I am getting infrared thermostat to see what the actual difference is but it's almost too hot to put your hand on while the port side riser stays nice and cool.
Any ideas I'm really hoping to straighten this out and get out this weekend its been a busy off season 2 total rebuilds.

My twin 502's do the same thing. Infrared thermometer found a 30 degree difference from starboard side to port side. Port side runs approx. 30 degrees cooler. Everything seems to be operating normally. I have new impellers, new water circulating pumps and I also removed a starboard riser to check for clogs or corrosion and it was fine. Maybe this is normal....Not sure though??

My motors have been the opposite. Port side is usually warmer. I've verified the temps with an engine scane and the port side usually runs approx. 10* warmer.

Diggin- I checked it today and I have the same 30-35 degrees difference with an infrared. But my portside motor has no difference in riser temperature. Engine stays at operating temp I am just going to put it in tomorrow and hope that it does what it is supposed to.

Mine has seemed to operate fine even with the difference.

Are you running a circulation pump or a crossover? A friend of mine had that issue when he switched to a crossover - it introduced the water at an angle that sent substantially more water to one side versus the other. I think he had to put some type of restrictor in to limit the amount of water to one side.

I am running a circulation pump.