HJ pretty much hit it. They're really tail-heavy because of trying to get everything under the cowl to make it appear more realistic and with the radio box so far aft the boats handle more like a flat-bottomed boat than a true hydroplane, Pro Boat boats, not just yours in the gas and nitro versions (Which BTW puts your in the wrong forum here seeing how it's gas, not nitro powered) just have a lot of issues out of the factory. Mostly with the little things that all add up, flex cables installed improperly that cause breakage, a rudder that isn't made to break away in case of hitting something (Pro Boat actually ran out of replacement rudders at one point as it was covered under their warranty) and other little bugs. Had they moved the engine and radio box further forward plus fixed what all was wrong with it then they in turn would have sold more of these. There was no big name that anyone really knew that did the R&D work like AquaCraft who has Mike Zaborowski. They've got some guy named Darrin (sp.?) who later I found out about but still not a name that most of us know. I've know Mike since long before he went to work for AquaCraft and know his race record.
We're not trying to embarrass you or anything close to that, just filling you in with the facts. Good luck on getting what you can out of it as there may be someone out there looking for just what you have.
The other companies have also been know to put out some duds like AquaCraft. The V-24 was a joke as the hull separated at the seam. The Fuji engines were junk. That's why they made a Rio 51 Z version as they started putting Zenoah's in them. They companies start with a boat and a price point then do what they can to keep the price reasonable even if corners are cut.
For $1,500.00 I can honestly build a boat that will run at twice the 35 MPH and out-handle that boat with top-of-the-line equipment.