RE: dual motor esc
bebopin,
Its entirely your money and you can do whatever you wish with it but remember, ESCs that are made for cars are meant to be air cooled and not get wet. If you purchase one for a boat they will be marginal at best. If I were you (and I buy ESCs so in a way I am) I spend the money and purchase ones specifically for marine use. In many cases they are actually cheaper than ones for cars. I am partial to either proboats ESC ($40.00 & water resistant) or for scale MCD makes some really nice ones. If your into hot setups like dual motors and such I recommend RCHydros ESC's A good one that will handle 90A will run around $90.00. They are water cooled and water resistant. If you splash water on it no big deal. If you get an EVX or any other car ESC wet well, you probably will be going to buy another one.
Like I said, its your money and you can do whatever you wish with it. I just thought I would offer my humble opinion.
Best regards,
Pete