Yeah, thermostat occurred to me but exhaust elbow is also a good idea, we've come full circle on this thread. I am going to replace both I suppose, couldn't hurt and the engine is old enough. Really paying for my sailing days this year. Thanks for all your advice.
Pulled the old thermostat, definitely rusty and corroded. New one is in and didn't overheat on the short trip back to the mooring. I'll put her through the paces on friday, hopefully this was it.
