I recently bought a boat with a 1981 - 115 johnson, i got it right because the previous owner said the "buzzer keeps going off within a minute or so", he had the t-stats replaced, did not solve the problem, my first thought was an impeller kit, being as it sat in his garage for six years, after checking the compression , each reading 120, i bought it. well, now that i own it, i cant stop it from overheating. new impeller, t-stats(again), deflectors in block, head gaskets, carb kits, head gaskets, the darn thing still overheats to over 220* in less than a minute , maybe two. water comes out the tell tale strong and steady, when revved up, it comes out of the two relief ports in a good solid stream. when i pulled the heads, i noticed that the cylinders still had the crosshatch in them(good), any help is appreciated!!!
When in doubt, use the sledge! Are you on the water or running muffs when overheating?? You said when revved up it comes out of the relief ports, so I am going to assume you are on the water. I think we may be getting somewhere when you said the water entering the stat area is HOT! Might be grasping at straws, but out of ideas, could you somehow have an exhaust leak superheating the cooling water? Im not even sure that would cause the overheating that you are talking about, but like I said, grasping at straws.