Yes zero vibration below the 3400 rpm mark. While on the boat last week for attempted impeller change I did notice the vertical motor mount bolt (into stringers) washers loose. That will be my first adjustment then hit the water again and see what tightening nets vibration-wise.

Thanks for everyone's input to date, very helpful and gives me a lot of points to check.

I guess I have my answer. SB engine 3 of the 4 vertical forward mount bolts will not tighten, just spin. Port 1 of the 4.

Keith