2004 yamaha 225 four stroke overheating???

My 2004 yamaha 225 four stroke is overheating. I replaced the water pump a month ago (for precautionary reasons only)...fished a couple of times...no problem. I took the boat out last weekend and noticed no water pressure reading on the guage although th motor was "peeing" fine. I went back to the dock thinking it was a simple blockage in the tube going to the guage, which it was. After spending about 20 min. cleaning the blockage the overheat alarm went off. I replaced the t-stats...port side was stuck closed - starboard side was severely corroded. Problem solved right....WRONG....the motor still overheats at idle and the pee hole barely drips at the dock. I disconnected the alarm sensors one at a time to determine if it was one side of the block or the other...it is the starboard side that is overheating. When I flush the motor with a hose no water comes out the pee hole...it appears the majority is coming out the exhaust. The motor does not overheat while running..only at idle. A friend told me this particular motor was having problems with an adapter plate causing it to overheat at idle? Can anybody help?

[boats.net]

Start by checking water pump to make impeller and housing are not the problem. Next you can remove exhaust plate covers to see if any blockage or corrosion present to get an idea if needs to disassembled for more cleaning..