36
Engine foundation
Aligning the boat
The installation work is made easier if the hull is
aligned horizontally before starting. Block up the hull
so that the calculated water lines, both longitudinal
and transverse, are parallel with the horizontal plane.
A spirit level is a good help.
Check when manufacturing the bed that the upper bed
plane, the mating plane, is parallel and correctly posi-
tioned in relation to the centre line of the propeller
shaft. A guide sleeve with the same diameter as the
propeller shaft can be used in the stern tube to help
with the alignment of the bed.
General
The engine bed should be dimensioned so that it is
rigid in all directions to distribute the load as much as
possible into the hull. The greatest possible area of
the engine bed, and with cross members, must be
fastened to the hull to give the best noise and vibra-
tion insulation.
Design
The bed should have a design basis that enables it to
absorb by an adequate margin the engine torque, the
compressive force of the propeller, and the dynamic
forces (mass forces) that occur during movement in
rough sea.
When designing the bed it is important that there is
sufficient space under the engine for the movement of
the engine, and that there is also access to the in-
spection covers (certain engine versions).
If possible the bed should be designed so that the re-
verse gear and flexible coupling can be dismantled
and lifted out separately.
When designing the bed the dimensional drawings for
the engine and the boat should if possible be used to
check the space round the engine and the height and
position of the bed in relation to the propeller shaft.
The height depends on whether a flexible engine sus-
pension is to be used or whether the engine is to have
a rigid suspension, and the inclination of the bed
should correspond with the inclination of the propeller
shaft. The height should include a shim of 10 mm
(0.4”) avoiding the bed being too high.
It is important to drain any water around the engine
bed to the location of the bilge pump.
The figure to the left shows an example of a well-de-
signed engine bed.
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