Hello Dan,
Many good options for power systems out there. First I would skim through the NAMBA rule book for FE classes. The Sport Hydro class in particular has some specific rules like the gas boats do. The most important is the length limit for the respective classes. 34" for P/P-Ltd and 40" for Q. S&T are are 60"
The P or P-Ltd class is a good place to start out. There used to be a huge difference between the open power system P class and P-Limited, but now with the better motors there is little difference unless you design a specific boat for high power and heavy weight of a full P system.
For P-Limited there is a very good power system recipe.
Motor:
Tenshock 2240 6T or 7T. The 6T is a 2700kv motor better suited for riggers and the 7T is a 2300kv motor which works well for either. These motors come with a 38mm can diameter which needs to be machined down to 37mm to be legal in NAMBA. If you don't care just leave it as is. A lot of guys are sending old gold can Aquacraft motors to Don Huff who can rewind them. This is a very competitive motor and similar to the Tenshock 2240. If you would prefer a more inexpensive motor to begin with look at a
Leopard 3674,
TP3630 or a
SSS 3674. Shoot for a KV range between 2200-2700kv.
If you want a full P system let me know and I can list out the full P power system options.
As for ESC's, if you want datalogging get a
Castle X8S hydra. This is a 300A ESC that is also waterproof. If you don't care for datalogging and want a cheaper option many people run the
OSE Raider 150. This is not quite as capable as the Castle ESC, but it's a good controller for the price. You will want to keep the all the wires short so layout is also important.
Lipos: For sport hydro I would recommend a pair of cells to straddle the motor and ESC. 3000-5000mAh per pack is what most racers will run. So you want a minimum of 6000mAh combined up to 10,000mAh total which is the NAMBA legal limit. For a rigger you might find a single larger capacity pack fits better. Many guys are running 6000-7800mAh single packs.
Look at
SMC,
Dinogy,
RoaringTop and
Turnigy Graphene. You will want 60C or better for most batteries unless you run a pair of large capacity packs then you can drop down to 45C.
Most guys run .150 cable with a teflon liner for the P-Limited power systems and .187 for full P. Build the stuffing tube from 1/4" brass and you have the option of running either cable.
That's a start. Keep the questions coming.
