It can be a bit of an acquired talent. Mercury recommends doing it in forward; just sayin." I do it in neutral because it is a lot more defined than forward, where the cam can swing way out of the way, if not careful.
First, make sure the splines are clean and lubed.
Then look up in the driveshaft housing and make sure something isn’t blocking the driveshaft splines, like part of an oil seal or something.
The biggest problem is usually that the shift splines won’t align because of wear or over-twisting of the shift mechanism, overall. First look closely at where the lower unit’s shift splines are clocked. Then, look carefully at where the mid section splines are clocked. You will probably see they are not just set to go right together. If you can determine which way things have to slightly turn, to come into alignment, then hold/turn the shift handle slightly, that should help it align. Be aware that the reverse lock cam can cause its own twisting force, which you will have to account for.
If that doesn’t work, then try it in forward. The larger available arc of the lower shift shaft in forward may help it align better. Also, you will not be fighting the reverse lock cam. Just be SURE that you have forward, neutral and reverse, when you’re done. (You may have to turn the prop shaft a bit for it to go into reverse, when hand-testing.)
All these words make it sound harder than it really is. I’m just trying to cover everything I can think of in one post…You’ll get it….
Long live American manufacturing!
.
