PRACTICAL BOATER | SEAWORTHY
CAPTAIN FRANK’S SEA CHEST OF HORRORS
Scary things you really never want to come across on your boat BY FRANK LANIER
WHILE THE OLD AXIOM “LET SLEEPING DOGS LIE” may be sage advice when dealing with Rottweilers, as a marine surveyor it’s definitely not the attitude to have with boat maintenance. All boats have sleeping dogs that should be coaxed out before they have a chance to wake up and bite the captain. To visually assist
in your mission to identify and head off potential problems, hop on board, buckle in,
and keep your arms and legs inside the car at all times, as we take a ride through
the cavalcade of maritime perversions I like to call “Captain Frank’s Sea Chest of
Horrors.” All the more shocking because they’re true!
NUTS TO YOU: Want to start an argument in most any boatyard? Find a boat where the
shaft nuts are in this configuration (thick nut first, thin nut last) and tell the owner or yard
manager who installed it that they’re backward. It seems like a no-brainer that the larger nut
against the prop would do most of the work and that the smaller nut should go on second,
to kind of hold it in place. In truth, however, it’s the smaller nut that should always go against
the load because it is the “jammed” nut, not the “jam” nut. When the second, outer nut is
tightened down, it compresses and deforms the inner nut a tiny bit, rotating it a fraction of
a turn. This effectively unloads the threads of the first nut and engages the threads of the
second nut. Thus, the top or
outer nut actually takes all the
load. As the larger nut has more
thread area (and more holding
power), that’s the one you want
as the outer nut. I see prop nuts
installed backward all the time
while surveying. Will the prop fall
off because of it? Not likely. But
who wants to find out?
ROTTEN TO THE CORE: Drilling holes
through cored decking without taking the
proper precautions is asking for trouble.
Leaky lifeline-stanchion mounting bolts,
above, (most likely due to failed caulking)
have allowed water to enter the cored
decking beneath. The mounting nuts are
drawn so tightly they’re crushing the
panel, no doubt an attempt by the owner
to not only keep the stanchion from wiggling, but also to try and stop the leak
(note the inadequately sized washers and
lack of a backing plate). In a perfect world,
your boat’s manufacturer has anticipated
where all deck penetrations are necessary
and has “de-cored” these areas by reverting
to solid fiberglass, allowing you to mount
hardware without drilling into the core.
But in the case of new installations, your
chances are slim to none that any of these
areas will coincide with whatever aftermarket doodad you want to mount, meaning
you’re going to have to do it the hard way.
Anytime you screw or drill through a cored
panel, the first rule is properly sealing the
core against moisture entry.
No backing plate, nuts tightened too
far, and incorrectly sized washers are
all leading to a leaky lifeline stanchion,
below. The photo on the left shows how
it should be done.
For detailed instructions on drilling
through a cored panel, see this article