Guys, you are all missing several things that are probably issues and why the boat won't plane out or turn:
- The boat is probably tail heavy. Look at where the engine, tuned pipe and radio are located. All are either mostly or totally behind where the CG should be. First thing I would do is find out where the boat balances at. If it's more than 1.5-2" behind the sponson transom, that is part of the problem. The prop can't lift the rear of the boat so it's dragging the transom and putting more load on the engine, slowing it and the boat down
- As mentioned above, the prop is probably too large. Most scale boats run between a 57 and 60mm prop using an .67(11cc) nitro motor. Some can run a bit larger, depending on weight and set up. I would drop down to a 60mm, preferably a lifting prop. An Octura 1460 or similar might be a better place to start, then move up to something larger if the boat shows it can handle it
- How much time do you have on the engine? If it's not broken in, it's not up to full power yet and isn't turning the RPMs to get the speeds you're looking for
- That turn fin is garbage, replace it. The fin looks to be a piece of bent metal, not a real fin and solid bracket. It's very possible that it's flexing in the turns and not doing it's job. It's also too narrow to really be effective
- How much throw do you get at full left and right when you turn the rudder? The rudder on my scale 2000 Elam Plus swings 35-40 degrees to the right and it can paint the buoys on a regulation course(too bad the driver can't) while to the left is slightly less since the boat isn't designed to turn that direction
These are the areas I would look at to start with. An improperly balanced boat isn't going to run correctly and that is the first thing I would look at, hence it being #1 on my list. When Pro Boat came out with their little .15-.18 powered boats, they were very tail heavy and wouldn't run without major reworking. I know many that didn't know hydroplanes first response was "The wing isn't set right, the rear needs to be lower to lift the boat!!!!", something that was totally wrong. Those that took the time to rebalance their boats ended up with a boat that was decent. Those that didn't usually ended up selling them on Fleabay for pennies on the dollar.