Full-season boaters like the convenience of walking down to the dock, stepping aboard their boat and driving off. Leaving the boat in the water all the time is not the best path to longevity for their investment, however. That is why most boat owners install a boat lift next to the dock at their vacation hideaways on lakes and waterways. Here is a homemade unit that should fill the bill for craft up to about 18 feet.
Many elaborate lifts are on the market. In this case, simpler is better. This unit both looks and works similarly to a boat trailer frame albeit without the axle and wheels. Instead, it has three legs where the wheels would normally be. The legs are adjustable galvanized square tubes with length adjustments being locked by top-mounted through-bolts.
The key to this lift is the pivoting trailer frame with keel-rollers. It tilts forward when the boat is driven nearly all the way forward in it. It is tilted back when relaunching the watercraft. Gravity and the outboard or stern drive do virtually all of the work.
This project is greatly facilitated by finding a used galvanized boat trailer. It already has the correct shape. Remove anything that is not part of the frame and its bracing. The frame is going to hold the boat about 6 inches off the normal water level. For lake shore installations, the water depth should be about 3 to 5 feet. Three 6-foot long 3/16-inch thick 3-by-3 galvanized steel square tubes comprise the legs. You also need three pieces of the same material 2 feet longer than your boat is wide. Two connect the rear legs, one on top of the other, and support the weight of the boat. The third points forward from the two and locates the front leg. All of these are fastened using galvanized hardware and 2-by2 steel angles, 1/8-inch thick. The three-legged assembly should be reinforced by the same size steel angles on crossing diagonals. Finally, eight keel-rollers with their mounting brackets will allow the boat to roll on and off the lift.
The trailer has hard pivots at about the point the wheels used to be. Normally, the front leg supports the trailer’s front tongue beam. A limit and movement guard made from sheet metal should come up off the underwater frame to surround the trailer tongue and limit its upward motion. Angled bunker beams under the angled V-shaped bottom should hold the boat upright on the keel rollers. The legs should be adjusted so the trailer is level port to starboard and fore and aft.
Angle the trailer frame back with the winch and drive the boat onto the lift as you would a trailer at a boat ramp. You may need to winch the last few feet. To re-launch, use the winch to tilt back the trailer frame, until the boat starts to slide. Then either push it back or pull it off the trailer into the water with the motor in reverse. Make sure a loose lanyard is connected so the boat will not drift away once launched.
