PART ONE: DRIVETRAIN INSTALLATIONS
A.hose will experience considerable twisting
loads from the rotating shaft’s friction in the
stuffing box. Top-quality exhaust hose is
ideal. Such hose does not compress very
much, so the fit to the hardware must be
close or the clamps won’t compress it
adequately.Stuffing-Box Water
Injection
Another stuffing-box consideration is water
injection. In the old days, the Cutless bear-
ing was lubricated by water forced into side
inlet ports in the external bearing housing.
These days, more often than not, the Cutless
bearing is installed so that lubrication wa-
ter can’t be ingested by this method. Instead,
you must install a water-injected stuffing
box to get continuous water flow onto the
rubber bearing. Water is taken off the main
engine raw-water cooling circuit and in-
jected into a port on the stuffing box; usu-
ally this port is^3 / 8 - inch (10 mm) diameter.
Note that water injection is below the
waterline. A failure in the hose or piping is
the same as a leak in the hull. You must use
rugged, top-quality materials. A1 fuel hose is
ideal. If more flexibility is needed, you can
use B2 fuel hose.Engine Beds
Though not strictly part of the drivetrain, en-
gine beds are every bit as important as the en-
gine mounts. If the beds are weak or flexible,
no amount of careful alignment will help. I’ve
worked on fixing several boats that had in-
adequate engine beds.
One of these boats was a twin 350 hp
(260 kW) MerCruiser, gas-inboard craft. Its
owner found a crack in the transmission
housing at the starboard engine’s starboard
aft mount. The crack went right through to
the transmission’s interior and leaked fluid.
He had the thing replaced. The new one
cracked again. So he had it welded shut (not
good practice, but he wanted to go cruising).
It cracked again. Next season, he replaced
the transmission once more. It cracked
again. Then he called me in. It had always
been the starboard engine that leaked, but I
took a look at the port engine and found a
crack beginning in the same place. The ar-
row in the first panel of Figure 3-14 points to
the crack.
What I then found was that the appar-
ently high, massive engine beds were in fact
hollow, with a wall thickness of less than(^7) / 16 inch (11 mm). The engine mounts were
bolted to small aluminum angles that were
simply through-bolted to only the inboard
Figure 3-14.
Cracked transmis-
sion and hollow
engine bed