Alignment issues
 

Has anyone seen a coupler that the alignment tool would not go into? I had one years ago when trying to align a '97 7.4L. I tried for days with the hoist and helpers and the tool and could get nowhere. Finally pulled the motor out and the tool wouldn't go in at all. The coupler looked fine. I put a new one on so that I could align the engine and all was well. A couple of weeks ago I was helping a friend with mainenance on a '97 7.4L and after greasing u-joints, we tried to check alignment. That tool would not even start to enter the splines, yet the drive would go on easily. Same thing that happened on mine in the past. When I brought my coupler in to the mechanic, he said he had never seen that before. Has anyone else??

Yes, happened to me, I think the splines get slightly deformed with wear sometimes, not really sure how it happens but it was like 5 thou smaller than the spec diameter

There is tolerance in the primary bore of the coupler. Thats why the stock merc alignment tool is so sloppy. I usually cut a zero tolerance tool for each coupler after I measure the primary bore. (not for those without a machine shop)

I've seen several couplers that the alignment tool would not go into. Most have been in high HP boats. Inspection revealed the splines to be worn to kind of a point. I guess they push out somewhat, preventing the alignment too from going in at all. The first one I ran across drove me nuts trying to align an engine that wasn't out. I use a spare input shaft to verify it's at least close to being aligned when I run across that situation.

Mine did that last winter. Everything looked fine but the coupler wouldn't even start. Grabbed some sandpaper and hit the outside edge for a couple minutes. Cleaned it up and the tool slid right in. It was like a couple small burrs on the outside edge wouldn't allow the tool to go in.

Did you do that with the motor in the boat?

Where can I purchase the aligment tool? I'd like to check mine during my winterization. Thanks

mercruiserparts.com

Thanks Brad.