I just purchased a 15' fishing boat with Johnson 48 HP outboard. The thing sat for a couple of years. I drained the gas and replaced it. It starts and runs just fine (a little rough at idle, but acceptable).<br /><br />When I rev the idle throttle, the engine revs to high RPMs as it should. In the water, when I put it in reverse and nail it, it revs to high RPMs. Of course it does not go very fast in reverse, but the engine is revving properly.<br /><br />When I go forward (full throttle) the engine only revs to about half power. I can only go about 7-8 mph at full throttle. But it sounds like it is running ok. I took off the engine cover and observed that when doing this, the little arm that swings when throttle opens is swinging the appropriate distance, same as when I rev the idle<br />throttle. Yet, it behaves and runs as if I only have the throttle lever half way down.<br /> 
<br />What gives?
<br />What gives?