RE: Gigantic scale rc boat project
interesting project, 3-4 feet is fairly normal for a scale RC boat, 6 feet is starting to get big, but not unheard of... i have a few projects in that size range that have yet to even be started.
considering what he wants, cost not being an issue is going to help. lol. first thing you need a controller, do a search for a marine RC radio's etc, they used to make some realy good ones a while back, may be able to pick one up cheap, some have realy nice setups for RC boats with dual-quad throttle and a steering type function that also shows your realitive rudder position. outside of that realm your probbly going to a aircraft style controler on a ground frequency. but if he wants a "realistic" controler that marine RC radio is your best bet.
as far as batterys, with big coke can motors like that, 12V gel cells are perfect, pretty simaler to a trolling motor but geared more towards RC boats, easy to manage, charge etc cheap and will give a lot of run time. if you have the room (with 6 feet of boat you should) use 2 for 2 motors, 2 batts, 2 ESC's and 2 motors is a good setup. you dont need high amp racing ESC's, high voltage yes but if its a scale boat dont waist your money on racing equiment.
ESC's look around marine boat pages, especially ones from europe, here in america the trend for RC boats usually has nothing to do with scale boating, kits etc.
if you find some links to european boat websites your likley to find a wider selection of ESC's and other equiement for larger scale style boats.
if youve spend time setting up a crawler and building a 6X6 emax, this is nothing out of your ability. especially if most of it is allready done.
"The harder part of this is he wants throttle sticks to move in sinc with the power going to the prop like a real boat and a steering wheel to move with the direction of the prop" a little more detail on that part please.