Greetings,

Subject vessel is a 1985 Sea Ray 300 Weekender with twin 260
Mercruisers. Engines have full fresh water cooling.

My starboard engine is overheating, and at cruise I noticed that the
flow of cooling water coming from the exhaust is significantly reduced
as compared to the port side.

What I've checked/done so far:

1. Through hull water pick-up clear, valve fully opened
2. Strainer basket clear
3. Impeller checked
4. Heat exchanger serviced

From what I can tell, the only other two points of possible
restriction would be at the riser (manifolds are fresh water cooled)
or the transmission cooler. Before I break out the wrenches, are the
transmission coolers copper based? Is it more likely that the
restriction would be at the riser, or at the transmission cooler? Am
I missing another area of concern?

Thanks!