M-384 Rudder Work

[maitiki]

<div>During my current haul out I noticed that the lower rudder
bearing was really worn. It appears to be strong enough, but
there is allot of slop present if you grab the bottom of the
rudder and shake it. I broke apart the lower gudgeon clamp and
am having a derilin bearing insert milled to take out the slop.
The rudder post opening will need to be enlarged slightly to make
way for the bearing. Additionally, I pulled the quadrant yesterday to repack the
rudder stuffing box. It had been leaking, was tired of the water
and wanted a fresh start prior to installing the auto-pilot.
Pulling the quadrant was easy as it appears that over the years
previous owners have sprayed the bolts. The packing looked ok and
just was really smelly. So some additional investigation reviled
that the rudder stock had some pitting just inside the packing
nut and leaking seems to be due to pitting not the packing
gland. The pitting was concentrated in an area of about 2
inches. In talking to a supervisor in the yard he said that s/s
needed oxygen to remain s/s and that stagnant water in the rudder
log had caused the pitting. For boats that have been used
extensively the movement of water in the log is enough to replace
the o2.
The major pitting was to a depth of about 10% of the OD of the
rudder post. This guy also said that the amount of pitting had
reduced the overall strength of the shaft to about 50% of it
original. I am having the post milled and filled for the
effected area before putting it back together. Have you ever
heard of this ?? Any thoughts ??
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[dicklatour]

<div>When stainless steel is oxidized it is called passivated and it becomes a very corrosion resistant metal for marine use. If contact with oxygen is removed and the oxidized coating is removed the stainless steel it becomes active and offers very little corrosion resistance.I not sure how weak this make a piece of S.S. that has become active and begun to corrode, but you can read about this topic in the "Boatowner's Mechanical and Electrical Manual" by Nigel Calder. See page 101.If you don't have this book in your boat library, it is well worth the money!
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