Yet another problem with stacking cinder blocks for support: All it took to shift
this boat dangeroulsy close to toppling over was a spring thaw. The blocks
shifted when the ground beneath them got soft. Fortunately, an alert owner
discovered the problem in time to have it corrected.
Never tie a tarp to the jackstands. The skipper of the boat above put a considerable effort into making sure his boat was prepared for winter, but carelessly
tied the tarp to the jackstands. Later that winter, winds buffeted the tarp and
the jackstands were gradually pulled away from the hull until the boat came
crashing over on its side.
positioned against the hull so that the boat’s weight is directed
down toward the ground. Misalignment of the stands will force
them out as the load is applied. Even if the stands are aligned
perfectly, safety chains must be used to prevent them from slipping
out from under the hull. Jackstands should be placed as far out
from the boat as practical to support the boat in high winds, with
at least three per side for boats longer than 26 feet and additional
supports at long overhangs. Plywood should be placed under each
base to prevent it from sinking into mud, sand, or even asphalt.
Even when stands rest on clay that seems brick hard, they can be
loosened by heavy spring rains, shift, and spill the boat.
While jackstands must be placed properly to prevent the boat
from falling over, the boat’s weight typically rests on its keel. Some
boats have specific requirements for support of the keel, but at
least one manufacturer warns against putting weight on the keel.
If the marina manager isn’t familiar with your boat, check your
manual or contact the manufacturer.
Keels must be supported by wide, thick timbers — the
wider the better to distribute the load. Cinder blocks are prone
to breaking and should not be used. On powerboats, additional
support is usually recommended for inboard engines, fuel tanks,
and heavy machinery. With outboard and outdrive boats, weight
should be taken off the transom by lowering the drive units onto
a block. After the boat is blocked, sight along the hull and keel to
make sure the jackstands aren’t depressing the hull. Check again
in two weeks, after the boat has had time to settle. The deck must
also be level, or water could pool and cause stains, mildew, and/
or gelcoat crazing.
Never secure the boat’s winter cover to the jackstands or support blocks. There are many accounts in the claim files of boats
that fell over after stiff winds filled the covers and yanked the