additional intermediate shaft bearings.
Their required locations are governed by the
shaft-bearing spacing we just reviewed.
There are three standard versions of interme-
diate bearings:1 .Intermediate bearings housed
entirely inside the boat Intermediate
bearings housed entirely inside the
boat are also termed pillow blocks
(Figure 1-12). They are relatively easy
to install and to align, but require
grease lubrication, often from a grease
cup. Pillow blocks must be inspected
and greased regularly, usually every
100 engine hours.
2 .A rigid stuffing box serving as an
intermediate bearing A rigid stuffing
box serves as an intermediate shaft
bearing (unlike a flexible or floatingstuffing box on hose). Rigid stuffing
boxes are somewhat more difficult to
align than pillow blocks. Older rigid
stuffing boxes sometimes used grease-
cup lubrication. Today, it’s standard to
lubricate them with water injection. See
the later discussion of stuffing boxes.
3 .An external intermediate bearing on a
strut—an intermediate strut bearing
Intermediate strut bearings are external
bearings, identical to the stern bearing
and strut described in Chapter 2. The
strut, of course, is shorter and closer to
the hull bottom. These bearings can be
the most difficult to align; however,
they are water lubricated by water flow-
ing through the bearing from ahead (as
is the stern bearing in the main strut).Intermediate strut bearings are usually
I-struts (also called P-struts), because they
are so much shorter than the longer stern
strut. Sometimes, however—when they need
to have a significant drop—they may be
V-struts. Generally, these struts will have legs
the same thickness and proportions as the
main strut aft, even though they could be
thinner due to the shorter drop. The interme-
diate strut shows at the arrow in Figure 1-13.
Note that on this boat, the main struts aft are
larger than recommended.PART ONE: DRIVETRAIN INSTALLATIONS
Figure 1-12.
Pillow block
Figure 1-13.
Intermediate strut
bearing (Courtesy
Chris Wentz)