i have a 1999 200hp yamaha saltwater series efi 2 stroke. i just did thermostats and water pump about 2 weeks ago. took boat out for the first time the other day. engine ran great all day, about 45 miles.when i was coming in to my slip at idle, my overheat buzzer went off.i shut down engine immediately and coasted into my dock. pulled engine cover and felt heads.one head was warm while the other head was extremely hot.pulled stats and both are working good.the tell tale has a good stream coming out of it. i pulled the plugs and all were oily so i don't think it is a head gasket. all help would be appreciated