Well, I found my vibration! I went to check the alignment on my 170 Merc/ Alpha one drive yesterday and I reached in and grabbed the drive shaft and can shake it all around. So my coupler is shot! I ordered one last night, 226.00 with shipping. Maybe this will take care of the vibration I've been feeling since I rebuilt the motor and drive. Seems its always something! This is the ONLY thing I havent replaced!!!! Will probably take a good day ta pull the motor and drive and get it in. Gotta get it right really quick, we are headed to Nags Head in 2 weeks!! Cant wait, We need a good vacation!!

:sun:

The couplers on those are known to fail, aftermarkets are readily available for them.

Is one of your prop blades dinged or nicked? Trimmed all the way in is running the prop at an angle that will bring to life any imperfections.

Im pretty sure its the coupler. It vibrates when running on the water hose in the yard, with the drive in neutral. I can shake the drive shaft inside the coupler. Does anybody know what the torque is suppose ta be on the rear motor mount bolts and the torque on the single nut on the front motor mount ? I cant find the torque settings for these mount bolts in any of my manuals.Thanks!

I can't remember what the torque spec was on those bolts, we rarely used a tourqe wrench on the rear bolts as most engien compartments didn't allow room for a straight extension and a torque wrench. I ususally had to settle for a swivell socket and my 3/8 impact. If I had to guess, arond 45-55 ft/lbs.
you kind of lost me on your description of whats going on here. You say you can reach in and move the drive shaft? Meaning you can reach behind the motor, between the transom and the engine bell housing and move the drive shaft? If you can do that, yeah sounds like you found your problem. You should also be able to look into the coupling hub with a flash light(drive removed) and inspect the splines in the coupler, they should be uniform with square peaks, if they look sharp on the peaks, the coupler is worn out, don't forget to check the input shaft for wear as well. The splines should bear square in shape as well, if they look sharp on the peaks, its worn. When r[placing the coupling, or any time the drive is removed, use specified drive coupler grease on the splined shaft

just my 2 cents
hows the prop is it bent or damaged look at it maybe thats the problem

The prop is a new stainless prop, with no signs of damage and it vibrates in neutral ,on the hose , sittin in the yard . Ive almost ruled the drive and prop out. I can reach over and behind the motor and grab the drive input shaft and shake it around inside the coupler, so im thinking thats gotta be the culprit. This old 77 V has alot of room around the back of the motor but I think Ill just pull the motor completely out ta change out the coupling. Looks like I gotta pull off the engine bellhousing to get at the coupling bolts and ta get it out of the bellhousing hole. It won't be to bad of a job being I already had it out before. Probably can do it in a day (I hope).Thanks for all the info fellas! Ill let you all know how it turns out.

:beer:

if you can move teh drive shaft like that, I would have to agree that its teh coupler, most of yhe boats i work on you can't get back behind there. Double check the gimbal bearing while you have the drive off

Will do!!! I replaced it when I rebuilt it but Ill check it out good when I pull the drive. Thanks again!!

:hi:

I blew a coupler one time in my 165 I/O and it was also the only thing I did not fix when I pulled the motor! It was at least easier to pull the motor the 2nd time:nut: