bass boat speed

I Bought A 1977 17' Terry Bass Boat (trihull) W/ A Merc 175 Hp. 6" Jack Plate. All The Way Down The Cav Plate Is Still Above Bottom Of Boat. The Mechanic That First Saw It Said It Must Fly. I Wish! 45 Mph Tops. I Know There Is More There But I Can't Seem To Get It. Prop Has No Writing On It But I Calculate It At 24-25 Pitch. Only Getting 4600
Rpms At Wide Open. Heres The Thing. Anything More Than Zero Trim Starts The Porpoiseing. As Soon As I Trim In A Hair It Stops. How Can I Get The Bow To Stay Up. If I Can Get It To Stay Up I Can Shift Spray From Center To Back And Run On Back Of Pad Instead Of Middle Which Will Also Get Me Into Rpm Range. I Have Shifted All Three Batteries To Rear And Raised Motor About 2".
Any Suggestions? Thanks

 

Sounds like you have too much prop for one thing. You can try transom wedges to reduce the porpoising tendencies. The motor should be o.k. where it is, the jack plate sets it back so you can raise it up some. Wouldn't think you'd need to move weight back with a 175 on a 17 footer! But your bow is down and trimming up causes porpoising