Virbation problem, Gimbal Bearing?
 

I put a new gimbal bearing in my boat this spring. 21' Scarab with 350 and alpha drive. I've just started to notice that when I start the boat up when it's sitting in the water on the trailer and the drive is trimmed all the way up, if I rev the motor to around 2000rpm a vibration starts in the back of the boat, then when I trim the drive lower it goes away. Is that a sign that the gimbal bearing is bad, or is that normal when the drive is trimmer up all the way. Is it just because the shaft it not straight and the u-joints get out of balance? When the boat is running at WOT (around 60mph) ther is no vibration at all. The u-joints looked good when I put the drive back on in the spring. I did'nt use an allignment tool when I put the new bearing in, but I didn't think I had to since I never touched the motor or moved the position. Is that vibration normal at high tilt angles.

This is normal it also will make a strange noise when it is in that position from the u joints at a bad running angle.

Yea, what thunder said, and you should really not run it over idle when trimmed up over the stops. It doesnt do the u-joints any good.

vibrator
 

like others have said it is not advisable to start let alone get above idle when in trailer position
I always drop the drives below full trim BEFORE starting.
Now then again with my cat I am able to leave the drives in full down position on the trailer without any trouble.
But if you are in the water already you sould be able to get at least at if not below full trim.

Keep doing what you are doing and you will learn how to replace u-joints :) The hard way :(