Boat Lift Sizing: Getting Capacity Right the First Time

The mistake that costs the most

Undersizing is the most common and most expensive error in this category, and it almost always happens the same way: somebody sizes the lift against the boat’s dry weight.

Dry weight is the hull and the engine. What the lift actually carries is the hull, the engine, and full fuel, full fresh water, batteries, anchor and ground tackle, safety equipment, electronics, a tower or hardtop if fitted, canvas, fishing gear, coolers and whatever else lives aboard.

On many vessels that totals thirty to forty per cent above the dry figure. On a boat with a large fuel capacity it can be more — fuel alone is roughly six pounds per gallon.

Then there is the fact that boats gain equipment over the years, and the fact that running a lift at its rated maximum shortens the life of every mechanical component on it.

Size for loaded weight, then add headroom. The cost difference between capacity steps is modest compared with the cost of discovering that the lift is marginal.

Work out the real number

Build the figure from the bottom up rather than trusting a single number:

1. Dry weight from the manufacturer’s specification, for your exact model and engine package
2. Fuel — capacity in gallons × approximately 6 lb for gasoline
3. Fresh water — capacity in gallons × approximately 8.3 lb
4. Batteries — typically 40 to 70 lb each
5. Hardtop, tower or arch, if fitted and not already in the dry weight
6. Gear — anchor and rode, safety equipment, electronics, canvas, coolers, tackle
7. Margin — because the figures above are estimates and the boat will gain weight

Add it up, and then specify a lift comfortably above the total rather than just at it.

Beam and hull shape matter too

Capacity is not the only dimension. The lift has to physically fit the vessel and support it correctly.

Beam determines the cradle width and how far apart the lift’s vertical members need to be.

Hull shape determines bunk configuration — where the bunks sit, at what angle, and how the load is distributed into the hull. A deep-vee, a catamaran and a pontoon are three different problems, and a bunk arrangement that works for one will damage another.

Transom and running gear determine how far aft the cradle can sit without fouling drives or propellers.

These are the reasons a lift specification starts with the make, model and length of the boat rather than with a weight figure alone.

Depth decides whether a lift is viable

A lift only works if the boat floats on and off at low tide. This is the single most common reason a lift is not practical on a given Northeast Florida property, and it has nothing to do with capacity.

Work from the boat’s draft, add clearance for the cradle and bunks sitting beneath the hull, and compare that to the water depth at the end of your structure at the lowest tide — not the average one.

On shallow frontage, the options are: extend the structure further out until depth is adequate, choose a lift style with a lower profile in the water, or accept that a lift is not the right investment on this parcel and put the money into a floating platform instead.

We would rather tell you the third answer than install something that strands your boat twice a day.

Duty cycle and drive type

How often the lift runs matters as much as what it lifts. A boat used most weekends cycles far less than one used several times a week, and lift components are wearing items with finite cycle lives.

Drive type, motor rating and cable specification should reflect actual use. For a high-cycle installation — or any commercial application — this is worth specifying up a step.

Covered or open

A roof over the lift bay protects the boat from sun and rain, extends the life of upholstery, canvas and gelcoat, and makes the structure far more pleasant to work around.

It also adds significant wind load, which has to be carried by the pilings. A covered lift bay is a structural decision made at piling stage, not a canopy added later.

If a roof is even a possibility, decide before the pilings go in. Framing for it costs little in the first pass and is a rebuild afterwards.

Maintenance that actually extends life

Three things make the difference between a lift that lasts and one that does not in this environment:

Rinse it. Salt air attacks everything mechanical. Fresh water on the drives, cables and hardware after use costs nothing and is the single highest-value habit.

Inspect the cables. They are the wearing item that fails most consequentially. Look for broken strands, corrosion and flat spots, and replace on condition rather than on hope.

Watch the bunk carpet. Worn carpet lets bunks mark the hull, and damp carpet against gelcoat for long periods causes its own problems.

More on installation and upgrades: boat lifts.