I recently purchased a 1985 Hunter 34. The deisel smokes at 2800 rpm and then stalls. I read that black smoke was caused by lack of air. The air filter was clean and there were no rags nor dead rats in the air intake. I opened up the engine hatch and found that the engine would run at 3200 rpm at full load (15 x 15 prop) and at 3800 rpm with no load. The only vent is on the port side near the stern of the boat and I am not sure it was furnished by the manufacturer. It is used by a fan to furnish air to the generator. What was the original design intent to provide air to the engine? Did any one else have this problem and what was the cure? All answers will be appreciated, even smart allec ones. Charlie