Originally Posted by Santelia
Ok Freespool, so you could be a precious source of first-hand information.
@ dennismc, do you mean that 2x320hp are not enough or that a 49' full displacement has a structural limit at a slower speed?
A full displacement does not have the length to do 15 knots or be capable of doing that, a full displacements hull speed at 49' probably would not do 11 knots either. It sounds like the boat you're looking at is a semi-displacement hull, that's ok too.
I'd hate to guess how much fuel those engines burn, but guessing with 320hp, they probably burn around 20-25gph for both at cruise rpm. I've always heard very good things about 903's and know of a boat that had 6500 hours on them without any rebuild or anything (a charter SF) and was running fine. I just have no experience with them.