OCTOBER | NOVEMBER 2017 BoatU.S. Magazine | 101
Damage could possibly cause overheating directly or a lumping up of the packing, which could stop the water and also
cause overheating. While the box is back,
you can also inspect the shaft, which is
normally hidden under the box, for signs
of crevice corrosion or other deformity.
It would be helpful to know whether
the overheating or cessation of the dripping comes first when you’re running,
but this could be difficult to determine.
You should also check out an article at
servicing stuffing boxes.
In search of the perfect anode
In a past BoatU.S. Magazine article, I
read that aluminum anodes are recommended in freshwater. I keep my boat
in an inland lake that has a channel
leading to Lake Superior. The boat is a
twin-engine inboard Tiara with bronze
rudder, prop, and stainless drive shafts.
The anodes on there now are made from
magnesium. Should I replace them with
zinc or aluminum?
Capt. Bob Meyers (ret.)
TOM NEALE: In our February/March
2017 issue, the article “Boat corrosion
protection with anodes” ( BoatUS.com/
Anodes), Charles Fort, associate editor
and director of our Consumer Protection
department, discussed this issue. His
“Anodes can be made of zinc, alumi-
num, or magnesium, and each type has
different uses. The majority of anodes
are the familiar “zinc.” While zinc anodes
have worked well for years, aluminum
anodes are even more effective because
they can create a higher voltage (driving
force) and have a much higher capac-
ity (useful life) for the same weight.
Aluminum anodes also do a better job of
protecting in both freshwater and saltwa-
ter. The majority of boats should be fitted
with aluminum anodes.
“Magnesium anodes are even more
powerful than aluminum (and more
expensive) and are best used only with
the advice of a specialist because, in some
situations, they can overprotect and cause
paint blistering and other problems.”
There is variance of opinion as to
whether magnesium is always best for
use in freshwater, as many maintain. In
order to feel comfortable with magne-
sium, I’d want an analysis of the metal
components of my boat by someone who
is familiar with the issues. Getting the
manufacturer’s recommendation should
be very helpful. I’d also get the recom-
mendation of the manufacturer of the
magnesium anodes that you want to use.
All anodes aren’t created equal. For
example, a magnesium anode may be
made of varying mixtures of magne-
sium, aluminum, and zinc. But so-called
“freshwater” can have different degrees
of conductivity and effectiveness as an
electrolyte. What one boater considers
to be freshwater may be quite different
from the experiences of another boater
elsewhere. Quick and easy answers to this
issue may not be all that quick and easy.
In the meantime, if I were using mag-
nesium, until I knew for sure what was
happening to the anode and the affected
components of my boat, I’d carefully and
frequently observe the state of my sacri-
ficial anodes, and any water-connected
metals (including those in the engine)
and bottom paint.
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