Hi, Dean
Considering the continous output of 5HP, the Thunderstruck 5KW may be the best solution for you, because you don't want to cool the motor.
The aspect that it comes as a whole package is certainly a plus, and I'm sure that Thunderstruck will be of even more help, if you let them use your project as a reference :-)
I think the price is not your first issue, as you want to sail safe with your self built wonderful boat.
You want a reliable solution, I guess.
Self-built kits made from chinese suppliers is bound to fail. (I was a supervisor in China before.)
You will need a reduction gear. A tooth-belt solution is easy to make, and quiet.
With the 5KW, select your prop for torque, not speed.
Your boat will not go faster than the hull speed anyway.
Sailboats CAN do under downwind conditions.
If you use sail, then you will shut off the motor, of course. Under sail, a folding prop will increase your speed.
For the weight distribution you can put some (or all) of the batteries in the bow compartment, using large squared cables to the stern.
LiFePO4 has a controller built-in, they are the expensive ones.
For cheap ones, you will need a separate controller, dedecated for LiFePO4.
Only connect such type of batteries when all (I mean ALL) have the same voltage (inside 0.1 V)
Will you be sailing in a lake or at the sea ?
Huge difference in corrosion protection, etc.
