Martin
Are you by chance thinking that the oil coming out of the exhaust shouldn't? Two stroke engines that are running properly will have oil coming out of the exhaust. If there is very little or none the engine is too lean. Boat engines usually need to run much richer than aircraft engines. Some of the oil carries some of the engine heat away too. If it is oil all over the inside of the hull from the exhaust just pipe it outside of the hull with a metal or silicone tube.