I have a 91 four winns 170 freedom with a 3 liter OMC sterndrive. The engine is basically new and runs extremely well except for one thing - when it's opened up to 3500 rpm or more, it sounds like there are 2 BB's bouncing around the rocker compartment - except I'm not sure where the sound is really coming from. There is no loss of power and it's not really during acceleration, just when it hits a certain rpm and then it's constant. It's NOT an even tick-tick-tick, but really like something is loose and flying around randomly. When I take the power down, the sound goes away. At low rpm, it runs perfectly smooth with no such sound. I replaced the head (to solve a different problem) but that didn't affect this issue at all so I really don't think it's anything actually loose or in the head and the pistons were clean. A few mechanics have looked and listened but couldn't figure it out. Last fall I saw a post somewhere that discussed something similar and the cause was the starter. In fact, it does kind of sound like the starter splines bumping against the flywheel or something and bouncing back. Has anyone ever heard of this? Any ideas? Based on some other threads, I need to check timing/advance, octane, coil, exhaust flapper and plugs but the big difference is this doesn't really sound like a misfire/detonation to me, it's not rythmic in any way and there is no loss of power when it occurs. I would really appreciate any help.
