Tight fit

Hi, I have 95' Bayliner fish and ski.   I have to change the bilge.   Is there anyway to enlarge the hole in the back with out cutting the fiberglass.   It's an outboard.    120hp.    I'm not that big but the access to area is small and I'm sure I'd get stuck.    What do the dealers do?

Sometimes you can take the rear seats out and access the pump from the other side.