The links below are just a sample of what's out there on the web. You'll see some of the very same company sites displayed more than once under different categories. Because pricing varies so much between companies, I tried to include a cross section. If you happen upon a link that's gone bad, email me at email@example.com and copy & paste the bad link from this page in your message and I'll search out a newer link that works.
The typical Flat Plate Boat Hoist is available, rated anywhere from 3000 lbs. to 8500 lbs. and lacking only a surface to mount to; an adapter sleeve and drum for wire rope hoisting. Looking at the specs for the smaller units (4000 lb. class) they have a travel speed of about 3 ft. per minute. You'll sometimes see these advertised as 'open' units because the wormgear is exposed. These units are usually covered in their entirety with a white plastic weather shield.
Adapter sleeve connects the flat plate hoist's
large diameter drive gear to the take-up drum.
Some examples of take-up drums.
The upper picture depicts a drum with cable winder grooves.
Please try to visualize what a completed system might look like from above with the original Fulton K1550 removed; a plate sufficient in size ("A" plate) to mount the flat plate hoist to, where the adapter sleeve is allowed to project through - along with a corresponding plate ("B" plate) attached to the tower face to which the drum is mounted and attached to the adapter sleeve. Both plates (A&B) welded together along their intersection would provide a simple solution to supporting both the hoist and drum. The two plates welded together as one, act to provide mounting for the flat plate hoist (rotational forces) and drum (tensional forces).
Rick Karlquist - N6RK has written an exhaustive, painstakingly diagrammed treatise on the subject of motorizing the tilt over function for those of you struggling with larger crank up & tilt over towers. Rick's paper is titled Using a Boat Lift Hoist to Tilt Over an HDX-5106 Tower. http://n6rk.com/boat_lift_hoist_tilt_over_tower.pdf
Thanks, Rick. 6-28-13
After several years of using a Harbor Freight 1300 lb. Engine Hoist to lift the two fly sections of my US Tower TX-455 into the air, Florida's salt air had ravaged it. I decided to build what I had envisioned in a drawing a few years earlier by replacing the engine hoist with a Aqua Marine Supply 4000 lb. Flat Plate Boat Hoist and take up drum through Lunmar Boat Lifts along with a pair of aluminum plates fashioned into a mount. Pictured above is the end result. Take a look HERE at some of my close-up project pictures.
Here are a couple of older pages out of AMS' old website. *Click on either picture to view a larger image. Click again to magnify*