I have a Johnson 115 (2000) that has a knocking noise. The knocking is in sync with the rpm and gets louder as I accelerate forward in gear. However, it is unnoticeable if idling or reved in neutral or reverse. Out of the water, however, there is no knocking noise; instead it sounds like a car without a muffler. The sound comes from the center of the prop where the exhaust exits. I know that outboards do not have mufflers and that when in water, the water acts as the muffler. I've previously heard this motor running in and out of the water and this noise is quite different, it's much, much louder than I remember; like a car with no muffler. I have taken it in to be assessed but the certified Johnson mechanic can't figure it out and to get a diagnoses may cost a lot more than what I've already spent as he continues to look. He put the computer on it and everything checks out OK, also the compression is fine. He doesn't think it is a rod or bearing. Any ideas out there before I have to spend more $ on finding the problem? Could it still be a rod or lower bearing? Could there be a blown gasket? Please help - thanks much!
