Boat-Lift Blues And Falling Boats
By Bob Adriance
Protecting your boat when it's on its lift is up to you. The devices are workhorses, but have their limits
Several years ago, a retired gentleman in Fort Myers, Florida, got some really bad news from his neighbor: "Your boat is sinking." Fortunately, the boat was next to its lift, so rather than hassle with emergency pumps, all the owner did was press the lift's "up" button and wait; the boat's salvation was at hand, or so he thought.
The lift's motor whirred away and the boat, with thousands of pounds of water still trapped in the hull, rose oh-so-slowly out of the water. Then, just when the owner was reaching to shut off the lift's motor, there was a loud snapping noise and in an instant the lift and boat were plunged back into the water. The boat landed on the twisted metal stump of the just-departed strut, punching a hole in the hull. Before he could find an emergency pump, the boat sank.
The owner learned a tough lesson about his boat's lift: The rated capacity (usually on a label) is its lifting capacity. A lift rated for 6,000 pounds, for example, is not designed to lift boats that weigh 6,100 pounds; there have been claims for lifts that failed when torrential rains or snow added considerable weight to a boat. Besides the lift itself, there are several other ways a boat hoist can fail. The most common, according to the BoatUS Marine Insurance claim files, involves cables that fatigue and break, either because of misalignment, chafe, corrosion, or a combination of all three.
Excessive chafe on the cable is typically caused by faulty sheave alignment, incorrect sheave groove diameter, or improper drum winding. Sheave alignment can be inspected easily by looking down the cable to make sure it's centered and fits neatly in the groove. Anything less than dead-on puts pressure where it isn't designed to be and will hasten the cable's — and the sheave's — demise. Misalignment may also cause the cable to jump out of the sheave.
Improper drum winding occurs most often when the cable is momentarily slackened, which can cause excessive wraps around the drum to backlash like line on a fishing reel. The cable becomes crisscrossed as soon as pressure is reapplied. The result is uneven wear and damaged strands, as well as a loss of cable "memory." The latter is what helps it pay out neatly onto the drum.
Excessive turns encourage a tangled mess; to reduce backlashes, at least two turns (but not many more) should remain on the drum when the cable is fully unwound. Note: Whenever a cable comes off the sheave, or becomes jammed, or there is an overrun on the drum, DO NOT use your hands to repair the problem. There have been several claims filed for people who lost fingers when a cable suddenly snapped back onto a turning sheave or drum. If possible, lower the boat back into the water to eliminate pressure — load — on the cable. Tools, not inexperienced fingers, should then be used to work the cable. If the problem isn't easily remedied, call the installer.
Maintenance TipsNothing lasts forever. Even if the cable glides smoothly over the sheaves and drum, it still needs to be replaced periodically. Internal abrasion occurs whenever strands work against each other under load. External abrasion occurs when the cable bends around the winch drums or spindles. How long a cable lasts depends on how often it's used. It also depends on where it's used — salt or fresh water — and the care it receives.
First, rinse saltwater off the cable every time you launch the boat. Especially in saltwater, cables should not be left overboard while you're out on the boat. Aside from keeping salt crystals out, galvanized cable requires a squirt or two of penetrating oil occasionally, to preserve the galvanized coating and minimize abrasion between strands. Grease should not be used, as it traps moisture inside the strands. Stainless-steel cable, which is more expensive, but holds up better in saltwater, also benefits from a few squirts of penetrating oil between strands. Note: Don't be tempted to replace galvanized cable with stainless steel; the two cables require different sheave and drum sizes.
Assuming cable is well cared for, how long should it last? Some experts say that, to be safe, galvanized cable should be replaced every two years. All things being equal, stainless cable will last longer, up to twice as long. There are no rules, however; expectations on a freshwater lake in Vermont will be far different than those in the Florida Keys. Strong indicators that the cable needs to be replaced include broken strands, kinks, deformities, and areas of heavy abrasion. In the BoatUS Marine Insurance claim files, the galvanized cables that broke tended to show signs of corrosion — rust. A slight discoloration indicates that the protective galvanized coating has been worn away. Concentrations of heavy rust indicate that the steel cable itself has lost considerable strength. Be aware, however, that internal abrasion and rust are hidden; a cable can sometimes fail without prior warning. When in doubt, replace the cable; trying to squeeze another year out of a $40 cable isn't worth the risk of dropping your boat.
The BoatYou can't hoist just any boat out of the water. Aside from making sure the boat and gear aren't too heavy for the lift, the bow and stern eyes on the boat must be capable of supporting the vertical loads. A cleat is intended to withstand horizontal loads and should not be used to lift a boat. Eyes at the transom may or may not be adequate; some are intended for waterskiers. If you're not sure, contact your boat's manufacturer. You can also contact a marine surveyor or go to the BoatUS.com message boards and ask other owners.
The surveyor's report noted the badly corroded cables should have been a warning that they were overdue for replacement.
Stern eyes, which will be supporting the boat's engine(s), must be especially stout and slanted so that the angle of pull will be directly in line with the cable. If stern eyes are set vertically, a spreader bar must be used so that the cables line up with the eyes. If eyes are slanted inward, the cables can be led to a single bridle or, depending on the angle, be separated with a shorter spreader bar.
Boats that are lifted on slings or a cradle, typically two I-beams, should be positioned according to the boat's weight, not its length. Because the engine, batteries, fuel tanks, and so on tend to be aft, most of a boat's weight is near its stern. Providing adequate support for the hull usually means positioning the cradle nearer to the stern with the bow sometimes jutting well out beyond the forward I-beam.
Limit SwitchesDepending on whom you ask, limit switches are a convenient safety feature that stops a boat's ascent at a predetermined height, or — the contrarian's view — limit switches are prone to failure and are unreliable. The latter says limit switches have a history of failure from corrosion and can unexpectedly fail and lift a boat into the top of a boathouse. Supporters counter that the technology has become more reliable.
Whatever view you have, if your lift has a limit switch, it's important to remain nearby to monitor the boat's ascent, make sure the cable is winding on the drum properly and that the hoist stops when it should. A master switch should be in view at the electric panel.
To Home Page
Rules For The Boat Hoist
- Take the plug out of the drain while the boat is on the hoist. If the plug is left in, rainwater collects and can wreck wiring and machinery. The additional weight can also collapse the hoist.
- Put the plug back into the drain when the boat is being placed into the water. Without the plug, the boat will sink. (You should leave the drain plug — or a duplicate — on the lift switch as a reminder.)
- Use penetrating oil (not grease!) to lubricate cable strands and reduce internal abrasion.
- Rinse off the cable and lift with fresh water whenever they've been dunked in saltwater.
- Don't leave cables dangling in saltwater while you're out on the boat.
- Don't use the hoist to raise more weight than it's designed for.
- Don't replace galvanized cable with stainless steel, or vice versa; they require different sheave and drum sizes.
- Don't carry people up or down on a boat. A boat lift is not an elevator. People jumping in and out of a boat create shock loads that strain the cable and hoist motor. The effect is multiplied with davits, which are cantilevered five or more feet away from its vertical support.