1990 sr sd 350 exaust steaming

[remarley]

I have a 1990 Sea Ray SD 350 with twin merc's bluewater 454's / V drive. The original engines have about 650 hrs. When I run her over about 2800 + RPM the starboard engine steams a little compared to the port engine. She doesn't run hot and there is no other effect on performance that I have noticed. Is this normal or is there a possible exaust manifold or other problem that any other owners may have experienced with this type of issue? Any advise will be appreciated.

 

[RaySea Girl 2]

Not sure if this is the issue (if there even is one. My 91 370 SB always had a little steam in the exhaust as well) but check the small poppet (sp) balls, shaft, and springs inside the t-stat housing that direct water to the exhaust manifolds. If those get stuck or corroded you can experience overheating in the manifolds.
Just a thought. I replaced mine after a dock mate with a former salt water boat experienced problems with his.
Ray

 

[fwebster]

Exhaust steam happens when hot exhaust gasses are near cooler water. The fact that there is a slight difference from one side to the other isn't cause for concern, unless there is a huge difference and engine temps are not normal. The reason there is a little difference is because there are plumbing differences between sides and one side has several gallons more coolant in it than the other due to the heat exchanger in the water heater. To be sure, check the manifold surface temperatures with an infrared thermometer and diagnose any reading that seem high when compared to the opposite side.