If your going brushed, I would suggest a pair 700 brushed motors with a 35mm to 40mm prop. Your could use a pair of 550's like in the ProBoat Pt-109, but they may not be enough.
I would think a pair of Traxxas Titan 775's or Mabuchi 775's You will need two Traxxas 16.8v ESC's. There are other brands. The older 14.8v Traxxas may work just the same, but you can go Lipo with the 16.8v
Get some Lipo batteries and a charger. Stop screwing around with lead acid batteries. Do you cary around a motorcycle battery for you laptop? What the heck is it with the motorcycle batteries? I have one to start my snowmobile, and it's a pain in the butt! Takes eight hours to charge the darn thing!!
11.1v 3s Lipo battery would be a good choice for brushed 700's.
Two Astro Flight 25 motors would work, but those are $390.00 each. Nice motors, but a little out of reach for most.
Graupner has the 700BB, but the price is just stupid for something that is out-of-date and almost obsolete.
I would use two M4 shafts with four blade 40mm plastic props. I would hook up two Turnigy 3974 2200kv motors with a 160 amp esc for each one. Program them for counter rotation and use a "Y harnes" to control them through the receiver.
I would use two 10000 mAh 7.4v 2s 40-80c batteries for each motor. You could go 11.1v 3s if you want.
This is just in theory, but it should move!!! It should rock!