doozy—is how to pull the shaft. Indeed, I’ve
seen boats like this and wondered how the
shaft was installed in the first place; clearly
it was from inside before the engine was put
in. This means that simply to change the shaft
(or the propeller), you would have to unbolt
and lift the entire engine out of the way! This
situation would elevate a mechanic to the
final stage: past swearing and apoplexy, all
the way to sheer joy—joy from contemplat-
ing the size of his bill!
Removing Large Rudders
On large boats, rudders and their stocks may
weigh over 300 pounds (140 kg). They are
awkward shapes to handle, and dropping
them could ruin steering alignment or worse.
On most powerboats and even larger cruis-
ing sailboats, it’s a good idea to install strong
lifting eyes on either side of the rudder. If
these are on the surface of the rudder blade,
they should be aligned horizontally fore and
aft to minimize turbulence. Alternately, flush
screw-in deck plates can be fitted at a hole
through the rudder blade, port and star-
board. This way the deck plates can be
removed and a padded hoist line run through
to lift the heavy rudder. Be sure the lifting
eyes are designed to take the full weight of
the rudder, with a safety factor of 3.
Rudder Palms
Most boats have a continuous rudder stock
running from inside the rudder up through
the lower rudder bearing and into the hull.
This is preferred because without a break,
the stock is strongest, and with no external
joint, it has the least water resistance. To
remove rudders with continuous stocks,
though, you have to raise the boat high
enough above the ground to drop the full
length of the rudder stock down through the
bottom of the boat before the bottom of the
rudder hits the ground. (You can also dig a pit
under the boat for this purpose.) Clearly, this
can be quite an undertaking on large boats.
For large vessels fitted with rudders—
with bearings above and below the rudder
blade, but never spade rudders—you can
eliminate this removal problem by cutting the
rudder stock in half just below the bottom of
the boat hull and joining the two halves of the
stock together with a shaft coupling. Cou-
plings used in this application are termed
rudder palms(Figure 12-23).
Rudder palms are best sized from stan-
dard SAE Type I (internal-pilot) and Type II
(external-pilot, straight-bore) propeller-shaft
couplings. The dimensions can be found in
Appendix C of my Propeller Handbookor in
ABYC standard P-6. In this application the
male-female protuberance around the center
can be omitted. It is possible to have a true
coupling fitting only at the upper part of the
rudder-palm joint. It can make good sense to
bolt this upper portion of the coupling di-
rectly to the top plate of a welded rudder. Be
sure that this top plate is thick enough to
accept the rudder-palm bolts properly (or use
a doubler plate) and that it’s wide enough to
accept the full diameter of the upper half of
the coupling fitting above it. Also, in steel or
stainless rudders, which bolt into such a top
plate, there should be stainless threaded
(HeliCoil) inserts in the bolt holes in the rud-
der top plate. Without these, the bolts will
seize over time and be nearly impossible to
remove.Chapter 12:Rudder-Stock Angle, Control, and Installation Considerations
Figure 12-23.
Rudder palm