Boat Lift Glossary

Boat lift dealers, installers, and manuals use a lot of shorthand. The terms below are grouped alphabetically. Where a term has a full guide, follow the link for the mechanics, numbers, and field procedures behind it.

A

AC motor

An electric motor that runs on alternating current from shore power, commonly 120 V or 240 V on lifts. AC lift motors are often single-phase capacitor-start designs. See AC vs DC boat lift motors.

Air-chamber lift

A floating lift that raises the boat by blowing air into submerged tanks, displacing water to gain buoyancy. See floating boat lifts.

Aluminum alloy

A blend of aluminum with other elements to improve strength. Structural lift members commonly use alloys such as 6061-T6, where "T6" denotes the heat-treated temper. See boat lift materials.

Ampere-hour

A battery capacity unit (Ah): a 100 Ah battery can in theory deliver 5 A for 20 hours. Used to size batteries for DC lifts. See the solar charger sizing tool.

Anode

A block of a more reactive metal, usually zinc, aluminum alloy, or magnesium, attached to a structure so that it corrodes instead of the parts it protects. Zinc and aluminum anodes are typical in salt and brackish water; magnesium is used in fresh water. See corrosion protection.

Approach

The path a boat takes into the lift, including room to turn and the effect of wind and current. A poor approach is a common reason boats end up crooked on the bunks. See dock and slip layout.

Auto stop

A control feature that stops the lift automatically at a preset upper or lower position, usually by a limit switch or sensor. See remotes and controls.

B

Ballast

Water carried in tanks or bags by wake boats to increase wake size. Fresh water weighs about 8.3 lb per gallon, so ballast must be drained before lifting or counted in capacity. See wake boat lifts.

Battery

Stores energy for DC lift motors; commonly a deep-cycle 12 V or 24 V system on lifts. Lead-acid group 24/27/31 batteries weigh about 50 to 75 lb each. See solar and battery problems.

Beam (boat)

The widest point of a boat's hull. Beam determines the minimum inside width between lift uprights or pilings.

Beamless lift

A lift with no overhead top beam, with the drive mounted low or on the pilings. See beamless boat lifts.

Birdcaging

A wire rope defect where strands spread apart into a cage shape, usually from shock loading or twisting. A birdcaged cable must be replaced. See cable problems.

Boathouse lift

A lift installed inside a boathouse or covered slip, often hung from the roof structure. See boathouse lifts.

Brake

A device that prevents the drive from turning backward under load when the motor stops. Some gearboxes are self-locking and need no separate brake. See lift slipping or not holding.

Breaking strength

The load at which a wire rope or component fails in testing. Working loads are kept well below breaking strength by a safety factor. See boat lift cables.

Bunk

A padded board or beam that supports the hull on the lift, usually running fore and aft and covered with carpet or a poly slick. Bunks spread the boat's weight along strong areas of the hull. See bunks and cradles.

Bunk carpet

Marine carpet wrapped over bunk boards to protect the hull. It wears and holds grit, so it is replaced periodically. See bunk materials.

Bushing

A sleeve that lines a pivot or sheave bore to reduce wear. Worn bushings cause wobble and noise. See noisy boat lift.

C

Cable

The common term for the wire rope that raises the cradle on winch lifts. See boat lift cables.

Cable drum

The cylinder the cable wraps around as the winch turns. Drum diameter and length set how much cable it holds and how fast the cradle moves.

Canopy

A frame and fabric cover mounted over a lift to shade the boat. Canopies add wind load to the lift structure. See boat lift canopies.

Cantilever

A lift design in which pivoting arms swing the cradle up and back through an arc, using leverage from a winch. Common for free-standing lake lifts. See cantilever boat lifts.

Capacitor

An electrical component that helps single-phase AC motors start. A failed start capacitor often causes a motor to hum but not turn. See motor troubleshooting.

Capacity rating

The maximum load a lift is designed to raise, as stated by the manufacturer, usually assuming the load is centered. See capacity sizing.

Catwalk

A narrow walkway alongside a lift or slip for boarding and access. See boat lift accessories.

Center of gravity

The point where a boat's weight effectively acts. Outboards and stern-heavy wake boats move it aft, which loads the rear of the lift more.

Chain drive

A drive that uses roller chain and sprockets between motor and winch. See drive systems explained.

Cotter pin

A split pin that keeps a clevis pin or sheave pin from backing out. Missing cotter pins are a common inspection finding.

Cradle

The frame that carries the bunks and the boat and is raised and lowered by the lift's drive. It transfers the boat's load into the cables, cylinders, or arms. See bunks and cradles.

Cross member

A horizontal beam running across the cradle or frame that ties the sides together and carries bunk brackets.

D

Davit

A crane-like arm, usually mounted on a seawall or dock, that lifts a boat by hoisting it from above at one or two points. See boat davits.

DC motor

A motor powered by direct current from a battery, often charged by solar. Useful where shore power is unavailable. See AC vs DC motors.

Dead wraps

The turns of cable that remain on the drum when the cradle is fully lowered. They reduce the load on the cable anchor; manuals specify a minimum.

Dielectric grease

A non-conductive grease used on electrical connections to keep out moisture and slow corrosion.

Direct drive

A drive in which the motor connects directly to the gearbox input without belts or chains. See drive systems explained.

Draft

The depth of a boat's hull below the waterline. Draft sets how much water you need over the bunks to float the boat on and off. See water depth requirements.

Drive-on port

A floating platform a PWC or small boat drives onto, with no motorized lift. See PWC lift vs drive-on port.

Dry weight

A boat's weight without fuel, water, gear, and sometimes without the engine. Always add these to get loaded weight. See the boat weight database.

Duty cycle

How long a motor can run before needing to cool. Lift motors are designed for short intermittent runs, not continuous operation.

E

ELCI

Equipment leakage circuit interrupter: a device that trips when current leaks to ground beyond a set threshold, commonly 30 mA, used on marina and dock feeders under NFPA 70 Article 555. See boat lift electrical.

Electric shock drowning

Drowning caused when electrical current leaking into the water paralyzes a swimmer. Most common in fresh water near docks with faulty wiring. See boat lift electrical.

Electrolysis

A loose term owners use for corrosion driven by electrical current, including stray current from faulty wiring. Strictly, it differs from galvanic corrosion, which needs no external power.

Elevator lift

A lift mounted to a seawall or dock face that raises a cradle vertically along guides. See elevator boat lifts.

End fitting

A termination on a wire rope, such as a swaged eye, thimble, or clip, that connects it to the drum or cradle.

F

Fetch

The distance of open water over which wind can build waves. Long fetch means bigger waves at the lift.

Floating lift

A lift supported by flotation that rises and falls with the water or the floating dock. See floating boat lifts.

Foot pad

The base plate on a free-standing lift leg that spreads load onto the lake bottom. Larger pads help on soft bottoms. See lake bottom conditions.

Free-standing lift

A lift that stands on adjustable legs on the lake bottom rather than on pilings. See free-standing boat lifts.

Freeboard

The height from the waterline to the top of a hull or dock. On floating docks, freeboard shows how much reserve flotation remains under load.

G

Galvanic corrosion

Corrosion that occurs when two different metals are in electrical contact in an electrolyte such as salt water; the more active metal corrodes. See corrosion protection.

Galvanized steel

Steel coated with zinc for corrosion protection, often by hot-dip galvanizing. See aluminum vs galvanized steel lifts.

Gear ratio

The number of input turns per output turn in a gearbox. Higher ratios give more force but slower lifting.

Gearbox

The enclosed set of gears that reduces motor speed and increases torque to turn the cable drum. See winch and gearbox maintenance.

GFCI

Ground-fault circuit interrupter: a device that cuts power when it detects a small current imbalance, typically around 5 mA for personnel protection, indicating current leaking to ground. Required on many dock and lift circuits. See boat lift electrical.

Guide post

A vertical post, often padded or with a PVC sleeve, that helps steer the boat onto the bunks. See guide posts and V-sides.

Guide-on

A general term for guide posts or rails that center a boat entering the lift.

H

Hand wheel

A large wheel used to crank a manual lift winch. See drive systems explained.

Hot-dip galvanizing

Dipping fabricated steel in molten zinc to form a bonded coating, covered by ASTM A123.

Hull

The body of the boat. Hull shape (V, flat, pontoon tubes) determines bunk or cradle setup. See adjusting bunks for your hull.

Hydraulic cylinder

A tube and piston that extends under fluid pressure to raise the lift. Seal wear causes drift. See hydraulic lift problems.

Hydraulic lift

A lift raised by hydraulic cylinders instead of cables. See hydraulic boat lifts.

Hydraulic pump

The motor-driven pump that pressurizes fluid in a hydraulic lift. See hydraulic lift maintenance.

I

Ice jacking

The upward force of freezing water gripping pilings or legs and lifting them. A reason to remove lifts or protect pilings in ice country. See winterizing a boat lift.

Isolator

A non-conductive washer, sleeve, or pad that separates dissimilar metals to prevent galvanic corrosion.

K

Keel

The structural centerline of the hull bottom. Many hulls are supported near the keel and along strakes or stringers.

Kink

A permanent bend in wire rope. A kinked cable is weakened and should be replaced.

L

Lay

The direction and length of the helix in which wires and strands are twisted in a wire rope.

Leg extension

An add-on section that lengthens free-standing lift legs for deeper water.

Lift travel

The vertical distance the cradle moves from fully lowered to fully raised. It must cover water level changes plus clearance. See the water depth calculator.

Limit switch

A switch that cuts motor power when the cradle reaches a set position, preventing over-travel into the top beam or unspooling the drum. See remotes and controls.

Loaded weight

The real weight on the lift: dry hull plus engine, fuel, water, batteries, ballast, and gear. Use the capacity calculator.

Lockout

Turning off and locking a breaker before maintenance so the lift cannot be energized.

M

Marine growth

Barnacles, mussels, algae, and weed that attach to submerged lift parts. See boat lift cleaning.

Mean high water

The average of high tides at a location over a long reference period, published by NOAA. Often used for lift and permit planning.

Mean low water

The average of low tides at a location over a reference period. Used to check depth for floating the boat on and off.

Mechanical advantage

The force multiplication provided by gearing, pulleys, or levers. See how boat lifts work.

Mooring

Keeping a boat in the water at a buoy or slip rather than on a lift. See lift vs trailer vs mooring.

Motor brake

A brake built into some lift motors that engages when power stops, holding the drive.

N

Nationwide Permit

A general U.S. Army Corps of Engineers permit that authorizes certain minor structures in navigable waters, subject to conditions. See boat lift permits.

NFPA 70 Article 555

The section of the National Electrical Code covering marinas, boatyards, and docking facilities, including ground-fault protection requirements.

O

OEM

Original equipment manufacturer: parts from the lift's maker, as opposed to generic. See finding boat lift parts.

Off-center load

Weight not centered on the cradle, which overloads one side. It reduces effective capacity. See lift raising unevenly.

Outboard

An engine mounted on the transom. Outboards shift weight aft, important for bunk and cradle placement.

Overlap wrap

Cable wrapping over itself unevenly on the drum, which crushes strands. See cable problems.

P

Parts of line

The number of cable segments supporting a load in a pulley system. More parts reduce cable tension but increase cable travel.

Pile cap

A cover on top of a piling that sheds water and protects the end grain or open tube.

Piling

A post driven or jetted into the bottom to support a dock or lift, made of treated wood, steel, concrete, or composite. See piling requirements.

Pivot arm

The swinging arm on a cantilever lift that rotates the cradle up.

Planetary gearbox

A compact gearbox with a central sun gear and orbiting planet gears. Usually not self-locking, so it needs a brake.

Poly slick

A low-friction plastic strip fastened over bunks so the boat slides easily. See bunk materials.

Pontoon

A boat supported by two (or three, a tritoon) tubes. Needs tube cradles rather than V bunks. See pontoon boat lifts.

PWC

Personal watercraft, such as jet skis.

PWC lift

A small lift sized for one or two personal watercraft. See PWC lifts.

R

Rated capacity

Another name for capacity rating: the maximum load the manufacturer says the lift can raise, usually assuming a centered load. See capacity sizing.

Receiver

The control box that accepts signals from a wireless remote and switches the motor. See remote not working.

Reeving

The routing of cable through sheaves between drum and cradle.

Remote control

A wireless transmitter for operating the lift from the boat or dock. See remotes and controls.

S

Safety factor

The ratio of breaking strength to working load. It allows for wear, shock, and uncertainty.

Seawall

A vertical retaining wall at the shoreline, often used to mount elevator lifts.

Section 10

Section 10 of the Rivers and Harbors Act, which requires authorization for structures in navigable waters of the US.

Section 404

Section 404 of the Clean Water Act, regulating discharge of dredged or fill material into waters of the US.

Self-locking

Describes a gear set, often a worm gear, that the load cannot back-drive. See gearbox maintenance.

Sheave

A grooved wheel that guides and redirects the cable. Its groove must match the cable diameter to avoid pinching and wear. See pulleys and sheaves.

Shore power

AC electricity supplied from land to a dock or lift.

Slip

The water space where a boat is kept beside a dock. See dock and slip layout.

Solar charger

A solar panel and charge controller that keep a DC lift battery charged. See solar boat lift chargers and the sizing tool.

Spur gear

A straight-toothed gear. Spur drives are efficient but not self-locking.

Stainless steel

Steel alloyed with chromium for corrosion resistance. Used for cables and hardware.

Storm surge

A rise in water above the predicted tide caused by a storm. See hurricane preparation.

Strand

A group of wires twisted together; several strands form a wire rope.

T

Thimble

A grooved metal insert inside a wire rope eye that protects the cable from sharp bending.

Tidal range

The vertical difference between high and low tide at a location. The lift's travel must cover it. See tidal and saltwater installations.

Top beam

The overhead beam across the top of a vertical lift that carries the winch and sheaves. Beamless lifts eliminate it. See beamless vs top beam lifts.

Transom

The flat rear surface of the hull where an outboard is mounted.

Tritoon

A pontoon boat with three tubes.

U

U-bolt

A U-shaped bolt used to clamp brackets to tubes and pilings.

UHMW

Ultra-high-molecular-weight polyethylene, a tough, slippery plastic used for bunk slicks and wear pads.

V

V-side

Angled side boards that cradle a V-hull. See guide posts and V-sides.

Vertical lift

A lift whose cradle rises straight up. See vertical boat lifts.

Voltage drop

Loss of voltage over long wire runs, which can stall motors.

W

Wake boat

A boat designed to make large wakes, usually with ballast. See wake boat lifts.

Wave clearance

The height between the raised hull and the water surface.

Winch

The drum and gearbox assembly that winds the cable.

Wire rope

Steel wires twisted into strands, then strands twisted around a core. Lifts commonly use galvanized or stainless constructions such as 7x19. See boat lift cables.

Worm gear

A screw-like worm turning a gear wheel at a high reduction. Worm gears at typical lift ratios are often self-locking, which helps hold the load. See winch and gearbox maintenance.

Z

Zebra mussel

An invasive freshwater mussel that colonizes lifts. See boat lift cleaning.

Zinc anode

An anode made of zinc, common in salt water.

Sources and further reading

• NFPA 70, National Electrical Code, Article 555, nfpa.org
• NOAA Tides and Currents, tidal datums, tidesandcurrents.noaa.gov
• U.S. Army Corps of Engineers Regulatory Program, usace.army.mil
• ASTM A123, hot-dip galvanizing
• Wire Rope Technical Board, Wire Rope Users Manual