I had the coupler go bad on our 86 SeaRay Mercruiser (Alpha 1).
I pulled the motor and changed the coupler, no problem. I've pulled the Ujoint from the shaft and using the shaft for alignment (yes, the shaft fits correctly in the coupler).
I can get the shaft to go into the coupler, but it's tight. Grease on the shaft shows that it's high and to the right. I have a dowel that I'm also using as an alignment tool.
When I peer through the bearing to the coupler, it also appears that it's too high and to the right a little (1/16th inch, perhaps a bit more). The bolts on the back of the motor to the drive housing has no side to side give.
Because the coupler is too high, I removed the "double" wound lock washers that were under the rear motor mount (I could see light between the fiber washers and the bottom of the rear mount with a light and mirror) so I changed the "double" wound lock washers with a single wound (standard) lockwasher. This appears to help the height problem somewhat, but it almost seems that it needs to come down more and still needs to move the motor to the left.
I've searched the archives and there was one comment that suggested putting the alignment tool in the bearing, that there was some adjustment there, but it seems to be very rigidly mounted (even the drawings in my manual show this).
Is there something that I'm missing here? Could it have been out of alignment from the factory?
Incidentally, I pulled the plugs and turned the motor over to make sure that the coupler isn't misaligned (turns over smooth), it's OK.