Re: stuck in forward- Nissan 9.8
You did not mention what model you have. Makes a difference.
You may not have any problem at all. Any OB needs to have the shaft turning in order to shift gears, since it is a mechanical clutch dog, and the cogs need to align in order to engage. When out of the water, you can turn the prop (slowly) while operating the shifter to see it it engages. Do not start the motor out of the water, even for a second, or you will likely damage that new impeller.
If in fact it still does not go into gear, and we're not talking about the remote cable adjustment (again, what model to you have?), then there are two possible problems:
If it is the old style (threaded rod) style shift coupler, you likely need to adjust the shift rod coupler; If it is the newer style coupler (with roll pins), make sure nothing is bent, then check to make sure you did not disturb anything internal to the LU.