engine vibration at higher rpm

[tidalwave]

I have a 4-stroke 60HP MERC BigFoot with an 11 pitch prop. At higher RPMs, (above 3500), I start getting noticeable vibration from the engine.
Below 3000 RPM there is almost no engine noise and no vibration.
Am I getting cavitation? Do I need to go to a 'longer' pitch on the prop?

[Chip Hindes]

Never heard of vibration being caused by the wrong prop; vibration is narmally caused by a bent, dinged, or unbalanced prop or a misfiring cylinder.

[Night Sailor]

I'm with CHip. Bent prop or misfiring engine. Ventilation or cavitation would be noticeable immediately with higher rpms from the engine, too.

[royntracey]

I'm betting Chip's right, I hit a small rock (ever so slight dent) then got vibration at high RPMs. A guy (with a smallfile) at the marina sorted it in around 5 mins.
Been good ever since.