We intended to have A/C installed in Mrs.E's boat during the layup last
winter, but things got busy and the plan was shelved, at least for a while.
With summer finally beginning to present itself and the humidity rising, I
decided to try installing a regular window A/C unit in the aft cabin access
hatch as a temporary solution. Bought a small chunk of marine plywood, cut
it to fit the hatch, sealed it with rubber strips to prevent water intrusion
and painted it white.

The acid test was two days ago with temps in the mid 90's and high humidity.
The little 10,000 BTU A/C unit was able to cool the entire boat down to a
comfortable 74 degrees.

Looks a little tacky, but it works.

http://www.eisboch.com/pangea2

Eisboch