[Chris Burkard]

Hmmm, vibration at idle, but not at higher RPMs? Rare, but I have seen it. I agree, engine alignment would be my first check. My second would be check the props. It is very common when props are first installed that they get hung up while they are tightening the nuts and they don't get fully seated on the shaft (this is why props should be lapped on with lapping compound and not just throw on and tightened). What happens is the prop wobbles at low RPM, but as you speed up, the force of the water on the prop actually seats the prop on the shaft. If this is your issue and you don't get it taken care of, you can damage the shafts eventually. In the future, make sure when the props are installed, they are lapped on. Good Luck.