Vibration in 2005 Merc 9.9 kicker

[Johnny B Bad]

I have a 2005 Merc 9,9 kicker. At trolling speeds it has a pretty significant vibration. You can feel it in the handle and if I let go the handle really rattles. The prop was slightly dinged when I got it and I filed the edges, but I do not think that is causing this. It even vibrates at approx. the same RPM when out of gear. Someone suggested that I just change the prop and change RPM to get up and out of that range, but it has a 6.5 prop on it now. Anyone have any ideas what might cause this? Thanks, John

[timinthegorge]

Don't know if the prop is the problem. I've got an 03' 9.9 Merc 4-stroke, and I hate rattles. I had a rattle I couldn't figure out. I mentioned this to Chris Sessions, who runs the same motor on his guide boat and he said it may be the cowling. There's an adjuster screw inside the cowling to tighten it. But don't tighten it too tight or you won't be able to open or close it. I tightened it, and that was the problem. Rattle gone....

Hope that helps.... Tim

[ForeverFishing]

Sounds like a bent prop or drive shaft. If the prop was dinged, this is likely, especially if the previous operator has a propensity for hitting the bottom and the previous prop was destroyed. If the vibration persists in neutral, probably its a drive shaft. If it only vibrates when in gear, you're lucky; you don't need to have the top end torn appart, only the bottom end. Id suggest taking the prop off, and running the motor at high RPM. If it still vibrates, you know its not the prop and probably is the shaft. If not, replace your prop or have it balanced.

Could also be a bad bushing. In any case, I'd not run the motor until you figure this out or you might do a lot more damage.