79 Sea Ray 260HP - I installed a rebuilt sea water cooled 350 engine and set it up for fresh water cooling with heat exchanger. Log type exhaust manifolds are clean and I have a 145 degree thermostat. The engine slowly heats up to 195 degrees and stays there at 3100 RPM and cools down at lower RPMs. Water pump is new but, I didn't inspect the exhaust flapper. My question is: can anything go wrong with the flapper i.e. get stuck and work as a heat riser?