A Venti 660 would be even better, as it has more torque.
Running these motors on more than six cells without watercooling is not advisable, unless you want to burn them up.
Watercooling the can is the bare minimum, adding brushcooling is even better.
Take a look at
www.offshoreelectrics.com in the tips and tricks section how to make can- and brushcooling, it's not that difficult!
Regards, Jan.
P.S.: If your Key West still has the original "brakes" under the hull, you may want to flatten those aswell, that will really make a difference...