US Patent 7850147 Boat lifting apparatus

This boat lift drive is used for raising and lowering a wide range of boat size. The boat drive is a two stage worm system and uses a drive motor having a motor shaft driving a first worm and a first worm wheel as a first stage, and driving a second worm and a second worm wheel, as second stage. At least one of said worm shafts has a copper alloy intermediate worm portion. A third stage is provided having a spool driven by the second worm wheels, the spool having a cable disposed thereabout for lifting the boat.