I just recently bought a 5,000 BTU unit that is a $100 window unit
converted to water cooled. It is realatively easy to do and is far
less expensive than a "marine" AC yet the only real difference is the
water cooled condenser.

Keith wrote:
I installed a Mermaid 16k unit several years ago and it's worked
flawlessly and quietly ever since. I'd recommend them in a heartbeat.
Great value and warranty. If you've got that much to cool, I hope you
have 220V onboard.