Parts of a Boat Lift – Labeled Four-Post Lift Diagram

All 16 parts on the diagram

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Four-post lift 11

Pilings The foundation of the lift. They carry the weight of the lift and of the boat.
Top beams Each carries a drive unit, a motor and a drive pipe. The cradle hangs below them on the cables.
Drive unit (hoist) The motor turns its gears, and the gears turn the drive pipe. Makers also call it the hoist or the gear box.
Motor It powers the drive unit. This lift has one on each top beam.
Drive pipe The drive unit turns it. The cables wind onto it to raise the cradle and off it to lower the cradle.
Cables They run down from the drive pipe. One goes to each end of each cradle beam, four in all on this lift.
Pulleys (sheaves) Here there is one at each end of a cradle beam. Running the cable round pulleys lessens the load on the drive unit.
Cradle beams Each has a cable at both ends. The bunks are fixed across them, and the boat goes up and down with them.
Bunks They are set to suit the shape of the hull. They may need adjusting for a different boat.
Guide posts They center the boat from side to side as it floats in. That sets it over the bunks.
Switch Up raises the cradle, down lowers it and off stops it.

Freestanding lift 5

Frame A freestanding lift has a frame of its own, often welded aluminum. It stands in the water on four legs.
Legs Each ends in a pad that sits on the bottom. The legs adjust to suit the depth of the water and to level the lift.
Winch Working it raises and lowers the boat. Larger lifts have an electric winch.
Wheel A manual winch has a large wheel to spin. A motor can take its place.
Canopy A fabric cover on a frame of its own. It keeps sun, rain and debris off the boat.

How this list was compiled: Every name checked on 2026-09-30 and kept only where two makers use it. Four-post lift: a lift maker's owner's manual with a labeled figure (https://iqboatlifts.com/wp-content/uploads/2023/04/4-Post-Superlift-Owners-Manual-600014.pdf: top beam, guide post, bunks, cables, cradle beam, sheave, pilings, motor, gear box, drive pipe, switch) and a lift parts maker's equipment guide and parts pages (https://www.bh-usa.com/wp-content/uploads/2021/09/BH-USA-Equipment-Guide-rev.-6-30-20.pdf: hoist or drive unit, drive pipe, cables, pulleys, cradle, bunk boards, top beams, cradle beams, guideposts, switch), with a third maker's installation manual for pilings, drive unit and pulley. Freestanding lift: the lift pages of three makers (https://hewittrad.com/products/lifts/hi-lift-vertical, https://www.shoremaster.com/boat-lifts/lift-models/vertical-lifts/, https://www.shorestation.com/boatlifts/freestanding: frame, legs, winch, wheel, canopy). Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; no maker's product, nothing traced. Licence: own work

How it works

The parts of a boat lift in two drawings: a four-post lift built on pilings, with a boat resting on its bunks, and a freestanding lift that stands on the bottom on its own legs.

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How a four-post lift raises the boat

Four pilings carry a top beam along each side. On each beam a motor turns a drive unit, and the drive unit turns the drive pipe. The cables wind onto the pipe and run down, round pulleys, to the ends of the two cradle beams. The boat rests on bunks fixed across the cradle beams, and guide posts center it as it floats in. Turn the switch to up and the cradle lifts the boat out of the water.

A freestanding lift

A freestanding lift has a frame of its own, standing on four legs on the bottom. A winch, worked by a big wheel or by a motor, raises the boat, and many lifts carry a canopy over the top.

Names differ by maker: the drive unit is also the hoist or gear box, and a pulley is also a sheave.
The guide posts only center the boat. The bunks take its weight.

Questions and answers

What are the parts of a boat lift called?

On a four-post lift: pilings, top beams, a drive unit and motor, the drive pipe, cables, pulleys, cradle beams, bunks, guide posts and a switch. A freestanding lift has a frame, legs, a winch with its wheel, and often a canopy.

What is the cradle on a boat lift?

The part that goes up and down with the boat. It is two cradle beams hung on the cables, with the bunks fixed across them. The hull rests on the bunks.

What are the bunks on a boat lift?

Carpeted boards fixed to the cradle beams. The hull rests on them. They are set to suit the shape of the hull, so they may need adjusting for a different boat.

What do the guide posts on a boat lift do?

They stand up from the cradle on each side and center the boat from side to side over the bunks as it floats onto the lift.

How does a boat lift motor raise the boat?

The motor turns the gears of the drive unit, which turns the drive pipe. The cables wind onto the pipe, and as they wind on they pull the cradle and the boat up.