Brian, as a proto machinist you certainly have an edge over most of us when it comes to modeling! I would make a custom mount out of billet with built-in water cooling.

Hobby People has several marine ESC's you can look at. Mtroniks is one of the brands they carry and Mtroniks is highly rated. The Xtra brand I believe is from Ripmax of England. You can also look at some others that are not carried by the major mailorder houses. Such as MCD from Canada and Electronize from England. An RCU member here has two of these motors in his Dumas Prime Time yacht and they are both controlled by a single Electronize esc.

-Tom