I have a go boston ticket. Haw can I get reservations to get on boat on specific hrs

You don't have to have a reservation if it's during normal hours. If it's after normal hours, I would say to call the park board.

Don't forget to take identification with you.

I would call them.

It's free to get on no card is needed. They ask for a donation which is optional. They do maintenance on it every Monday though so it's closed to public.