Re: lockout question
I don't think there is a reverse lock on an I/O, the hydraulics hold them down, just like on a T&T outboard. The two guys that have responded both know their stuff and I agree with them with the very limited experience with I/Os I have.
That said, I would check the fluid level in your T&T and cycle it several times to make sure the air is bled out. If that doesn't fix it then you may have valve problems.