Hydro-Hoist is one of several...Boat Floater, Econo Lift and others.

A motor with a blower attached about the size of a vacuum cleaner motor
blows the air out of the tanks. Each tank has a hole at the opposite end of
the tank of where the hose attaches, on the bottom that is about 4 inches in
diameter.

Two controls are in the enclosure that houses the blower, an electric switch
to turn on the blower and a valve. To raise the boat lift the valve is
opened and the blower motor turned on. It can be left on until air bubbles
out of the 4 inch holes and this is the maximum lift that can be obtained.
Once the boat is lifted to the desired height of to the lifting limit the
valve is manually closed and all the air is retained in the tanks. When the
boat is to be launched the valve is opened but the motor is NOT turned on,
the captured air from the rank escapes past the blower and the lift settles
into the lake.

I made a lift for my personal watercraft using 2 plastic 55 gallon drums,
some channel steel some 2X6's for the bolsters, a gate valve and an old
vacuum cleaner. My total cost was under $20. A purchased PWC is about a
thou!

Don Dando

Don Dando








dh@. wrote in message ...
How do the boat lifts that use air work? If they have a check
valve to let water out the bottom when they force air in, how
do they let the water back in to sink it? I thought maybe a
solenoid valve, but don't see any wires running to the float
tanks...only what appears to be an air hose. Is HydroHoist
the only lift that uses air? I read that they have a patent,
but they can't have a patent on the concept of using air
to lift a boat can they?