Shifter adjustment Q

[Hammerhead]

Rebuilt the carb, Runs good. :) Now I have to figure out why it's so hard to shift from forward to reverse or vise versa. Ya almost have to force it. It can't be right. I'm hoping it's just out of adjustment.
Question; ..is it alright, while on the trailer ..to run the motor at idle and shift in and out of gear during the adjustment process or even nessasary ??? Of course I'll have water to the intake and not get anywhere near the prop. If need be I can buy a tub and have the prop in some water if a load is required as I would a OB. TIA
I promise I'll buy a book soon as I find one. :-[