Crews Letter #2011 06 Corrosion and Explosion Have a Similar
Ring
Electrolytic Corrosion Can Be
Lethal
Good
morning Crew,
Max
Prop
For a
sailing boat, the same thing that pushes her through the water under engine can
be a real drag under sail. One solution
is a feathering propeller.
This
boat’s prop and shaft suffered significant corrosion. She is a Tayana 55. Her
engine is a Perkins range 4 135HP engine with Hurt HBW
450-2R gearbox, 2.06 ratio.
The
sacrificial zinc anode on the aft tip dissolved completely. The anode on the shaft is the second line of
defense. The screws were not tight. The anode turned freely on the shaft. The absence of a good connection put the
shaft and prop unprotected. This damage
happened in less than three months.
For
comparison, here is a new Max Prop and the 10 year old
one on Perception:
What
a difference a missing/disconnected sacrificial anode and 3 months can make. When a new prop and shaft were fitted to the
Tayana, her cruising speed was improved from 7 to 8.5 knots, same engine rpm. At $8.75 a gallon for diesel, that is an
improvement.
Steady
as She Goes,
Phyl
and Fred
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