bad vibration when turning or with the drive tucked in all the way?
 

Out for the 4th of July and was coming back after watching fireworks. I was idling along about 1500 RPM when the ass end of the boat started to drag on something. I immediately clicked the boat into neutral and raised the drive. It seemed OK after that but when I went out today the boat vibrated badly when turning and when getting on plane with the drive tucked in all the way. I am going to check the motor mounts to make sure they are OK. The prop looks OK except for some small nicks to the leading edge. The prop spins freely in neutral. It is a 2006 350 MPI magnum/ alpha setup and it has 227 hours on the engine and drive. The gimbal bearing still feels tight. what should I check next and what are the signs to look for?

universal joints.

Bingo...

Ding, ding, ding. We have a winner. Whatever you hit probably nudged a very well worn joint over the edge. I'd be willing to bet that it shakes pretty well when you trim it up too.

while your in there replacing your u-joints, change the gimble bearing also, it's time.

While you have it all apart its a good idea to do an engine alignment, you can get the tool on ebay for 45 bucks.

I am suprised that gimbal bearings would be bad after 227 hrs! What is the best way to check the slop in them? I am susposing that once I get the drive off it would be easier to see if they were worn.

The u-joints are what is bad. The gimbal bearing replacement is preventative maintinence.

Ok I just pulled the drive off and the u-joints look OK, no rust. they swivel freely. the splines on the shaft are straight, and the gimbel bearing spins smoothly and does not have any play in it. I am going to order new u joints and try that 1st.

I may as well change the gimbel bearing while I am in there too. Can the u-joints be changed without taking the whole u-joint assembly out of the drive?