I'm having a problem installing a bravo 1 drive after replacing the motor. I have checked the alignment, it seems to be good. The alignment tool inserts and removes easily. When I try to install the drive, it starts to go in then stops like it is bottoming out. I cleaned all the splines of the shaft and the coupler. I don't see any marks where it looks like it is hitting. Any ideas what else to check?

Have someone rotate the crankshaft while you try it. Possibly the splines are just not lining up. If that doesn't do it, loosen the two rear bellhousing to transom mounting bolts and try it. Sometimes even slide flat screw driver or a pry bar where you can raise the rear just a bit will do it.

I've had my engine out 3 times, and one of those times the drive just wouldn't slide in. I had left out a thin rubber flat washers, caught it soon as I loosened those two mounting bolts.

remove the 2 orings from the shaft and try it,might just be the o rings binding on the gimbal bearing,

Did you change the coupler by chance? Sometimes there can be interference between the shaft and a long sleeve coupler. How far from the helmet is the drive. If it is kind of close, it could be a shaft problem. I have seen guys pull the drive up that last little bit and destroy an entire engine in a very short time. One thing you could do is take the input shaft off the ujoint and see if it will slip in to the coupler, all the way. That would eliminate any question of the shaft/coupler being a problem.
If this is not case, then the previous tips may help you out.
Hope that helps.
Dick

Did the alignment tool slide all the way in and bottom out with a knock ( ridge step on tool hitting gimbal bearing ) OR did it just stop with resistance. The tool has to insert freely until it knocks against the gimbal bearing and then be able to pull it back out with two fingers.
If the drive won't go on easily the alignment is off.

Another check to do first is put Merc 101 grease on your alignment tool and slid in thru the gimbal bearing to you bottom out inside the coupler. Merc recommends a 2 finger pull out of your alignment tool - now check the pattern made on the grease to see how it looks - they should look like a even spline pattern all the way around and even plus even in length.

This will tell you if your aligned correctly and evenly plus can show you jacked up splines in the coupler. (the grease marks - patterns) Also stick a skinny straight rod up thru until it bottoms out inside of the coupler or even a measuring tape and measure that length to a spot like the outside edge of the gimbal bearing then do the same with your alignment tool, the lengths should be the same measurement.

You can try rotating the prop shaft as you push the outdrive on.

Thanks for the advice I'll be trying them this weekend. Hopefully I won't have to pull the engine and change the coupler.

Did you change the gimbal bearing as well?
If so, are you certain it bottomed out on re-install?

It turned out to be the alignment. After rotating the engine 90 degrees and adjusting a couple times the drive went right in. It just goes to show, once you think it is aligned test it a couple more times. I'm one step closer to getting on the water. Thanks to everyone for the advice.