Swap their Castle/Neu 2200 from their Emaxx, ERevo, in for the stock system ? Fine Design has alum water jackets for the Castle and Neu motors.
I found this on the Castle website :
http://www.castlecreations.com/products/neumotors/nm_boat_apps.html - nice chart for picking the best Neu motor for either "Sport" or Competition, all advising 8k-10k mAh....
And anyone plan on using A123 packs ? 6s2p on each side, for 19.8volts series, 4600mAh on each pack, wired in parallel for 9,200mAh of very safe, super durable, able to go below LVC, super fast charge. Expensive and heavy, but the extra weight will handle better if the water is choppy.