May want to give these people a call. i have had 2 of their units, no frills but wotk well. v vA 6,000 BTU unit wold be enough to cool a 260 Dancer in your part of the world.
http://www.arcticmarineair.com/
Previous owner put this crap on my boat. Best thing I found to remove it is a soap from Home Depot - ZEP, spray it on full strength and wash off with clear water. When you spray the ZEP on it will dissolve the polymer and turn it orange. Don't let the Zep dry on the gel coat. Just my .02...
I have done the Tenn-Tom once and the Tennessee River four times, the Cumberland once. Will probably do the Tennessee again, prettier and plenty of accommodations. About mid October is the time to do any one you decide.