Boat Air Conditioning

I like to have an air conditioned boat. My first installation was on my 18' Seaswirl. I used a 5,000 BTU window unit (<$100), some dryer hose and a homemade collection box to catch and direct the cold air.

 I mounted this air conditioner in an aluminum frame, but on a subsequent installation I just made corner supports for the base and secured the unit with a stout bungee cord.

The collection 'box' is PVC pipe with just enough cut away to cover the exit vent on the air conditioner. It's held in place by a strap with a snap.

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I ran the cold air into the cuddy cabin via dryer hose terminated by a single adjustable vent.

The two speed blower in the air conditioner was OK at night but wouldn't push enough volume mid day in the heat, so I put a bilge blower in the dryer hose (seen in the first picture between the bends in the hose). It was a little noisy but a small price to pay for the comfort.

I powered the unit with a Honda EU1000i generator mounted on the stern.

A cover for the front of the generator allowed us to run it underway even in salt water and rain.

A "T" and 2 way valve in the boat's fuel line after the primer bulb allowed me to fill the generator by switching the fuel flow to the generator line and pumping the primer bulb to put gas in the generator. It took about 100 squeezes to fill the empty Honda tank. Later I installed an electric fuel pump in the generator fill hose.

In addition to the air conditioner, the generator was also used to power a host of other devices, albeit one at a time.

I later upgraded the window unit to a 6,000 and made the air box out of doorskin, incorporating the bilge blower in the box.

This air box just hung on the window unit.

Then, for those days when we wanted to be cool underway, I would disconnect the dryer hose from the inside vent and route the cold air to a couple RV sanitation hoses which we could hang around our necks to blow cold air up our chins, or route the cold air inside a windbreaker.

Update 6/27/2015

The above is complicated and there seem to be other options -- like the coolers that blow air over ice, like for instance Icybreeze. There are also articles on DIY models for around $50. These units are spot coolers, not air conditioners. They will let you blow some cool air on yourself for a limited period of time. Here's some math:

A pound of ice is worth 144 BTU's.
A cooler can hold 30 lbs of ice.
Thirty lbs of ice is good for 4,320 BTU's.
Let's say you're thinking about cooling a small cuddy for overnight comfort. Considering an outside temperature of 85° I'm guessing that it takes a about 3000BTU's/hr to keep me comfortable in the small cuddy. This is based on my 5,000 BTU air conditioner running continuously (but without recirculating) to maintain ~70°. I'm thinking then that you'd you'd need to melt a little over 20 lbs of ice that first hour and you'd get 1 1/2 hrs out of 30 lbs of ice. But it's not likely that you could melt the entire 30 lbs in an hour and a half anyway. Want to go for 7 hours? That's nearing 150 lbs of ice for 3,000 BTU/hr. You could settle for less, but then you'd only be pretending to be comfortable.

Bottom line, you can blow cold air from a fan driven cooler full of ice but it's not likely that you'll find that approach workable for anything but temporary spot cooling.