I have recently purchased a 1962 johnson 28hp engine. WhenI bought it it ran fine, but after a few trips on the lake it has started to give me a few problems. When the engine is out of gear it runs and accelerates great. However if you put it in gear and load the engine it will not accelerate to full rpm. I have cleaned the carb and changed it's seals and gaskets. I have tried to adjust the HP misture but nothing changes. Does anyone have any ideas on what might be wrong?