Westerbeke 12B TWO Operator's Manual page 14

Engine Bolts
Bronze or stainless steel hanger bolts of appropriate size are recommended for use through the engine's
flexible mounts. Less preferred are lag screws because their hold on the wood is weakened every time they
are moved, whereas the hanger bolts stay in position. If the nut on top of the hanger bolt is removed to allow
the engine to be lifted from its resting place, the hanger bolt itself remains in place as a stud. Consequent-
ly, the bond between the hanger bolt and the wood is not weakened by the removal of the nut or the engine.
Foundation for the Engine
A good engine bed contributes much toward the satisfactory operation of the engine. The engine's bed
must be rigidly constructed and neither deflect nor twist when it is subjected to the engine's weight or to the
pressures that the boat may experience while operating in rough seas. The bed must keep the engine's
alignment within one or two thousandths of an inch of this position at all times. The bed has to withstand
the forward push of the propeller shaft which pushes against the thrust washer bearing which finally pushes
against the engine's bolts and bed.
In fiberglass hulls, we recommend that similar wooden stringers as in wooden hulls be formed, fitted, and
then glassed securely to the hull. This allows the hanger bolts to be installed firmly in the wood, thereby
reducing noise and transmitted vibration.
The engine support stringers must be as wide or wider than the engine mounting isolator. Isolator overhang
and/or rounded stringer surfaces are detrimental to the isolators' ability to retain vibration.
Preformed fiberglass engine beds, when used, should be of sufficient thickness to properly support the en-
gine and should be well-glassed to the hull when
installed.
The temptation to install the engine on a pair of
fiberglass angle irons must be resisted. Such
construction will allow engine vibration to pass
through to the hull. Flexible mounts require a firm
foundation against which they must act if they are
to perform their function. When possible, follow
bed design A and avoid bed design B (refer to
the illustration).
Supports between the bed stringers, and extend-
ing from the stringers to the hull, may be required
for proper support and to aid in the absorption of
vibrations.
Westerbeke Diesel Engines
GOOD
A
BAD
B
Note: Avoid excessive height, use
solid stringer construction
(Al.
12