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From: (no name) (no email)
Date: Fri May 04 2001 - 20:26:36 EDT
The four rubber mounts that have supported the (2,000 lb) Detroit 6V-53 in my
engine room since 1981 were made by a company called "Lord" whose name I was
very familiar with since my military days. They look like a mushroom with a
hole down the middle lined with a piece of metal tube.
The engine "stringers" are fore-and-aft walls in the engine room a bit above
the height of the crankshaft and far enough apart so the engine mounting feet
can fit between them. The stationary mounts are four angle brackets made of
welded up half-inch steel stock and bolted to the walls at each corner of the
engine with a 5/8" stack of thin galvanized sheet metal shims (about 20-30
per stack) cut to match the part of the angle bracket that bolts against the
wall. Moving these shims from port to starboard shifts the engine in yaw
and/or sway during the alignment process.
The engine mounts (feet) are in each corner of the engine and are supplied
with the engine. They consist of arms of a sort with a vertical hole (about
5/8") through which the engine can be bolted down.
The stem of each "mushroom" is pushed through a particular sized vertical
hole in the stationary mount with lubricant, threaded rod, nuts, washers and
a short piece of pipe until the bottom of the mushroom cap bottoms out on the
top surface of the angle bracket. Then I installed a longish bolt through
the metal tube, threaded part up, with a nut and large washers securing it to
the mushroom.
So now you have four angle brackets with rubber bushings with threaded studs
sticking up attached to the boat on top of stacks of shims. I put nuts on
each stud and ran them down to about an inch above the nuts securing the
bolts in the mushrooms and then dropped a washer on each one.
The engine is lowered so that the studs go up through the holes in the engine
mounts and the engine's weight is now on the mushrooms heads via the studs
(bolts). Another washer and nut is added to each stud to secure the engine
on the studs. These pairs of nuts are used to shift the engine in pitch
and/or heave during the alignment process.
(Pitch and Roll you all know. Yaw is a change in direction as if you are
changing course. Heave is up and down movement, Sway is side to side
movement, and Surge is fore and aft movement.)
When I first fitted up the engine I fitted a hard coupling to the shaft and
measured the errors in the directions that were correctable by shifting the
shims, that is side to side misalignment, or how much I had to move the
entire engine left or right to get the couplings to match looking down from
above them. I also measured with feeler gauges the gap between the couplings
at the 9 o'clock and 3 o'clock positions.
I then jacked up the engine, blocked it, and removed the bolts fastening the
angle brackets from the wall. I knew how thick each shim was, so I shifted
the number of shims equal to the sway error from one side to the other in
both the front and the rear angle brackets to center the engine.
I really can't remember how I figured how many shims to move where to correct
the yaw error so it is possible there was no error, but someone clever with
trig could figure it out easily.
Correcting the pitch and heave positions involve adjusting the nuts and is
much easier since you don't have to raise and block the engine, unfasten the
angle brackets, and shuffle the shims.
I did the whole job one day in 1980 and have never touched it since. I use
Federal Marine couplings which are a rubber bushing type and are quite
flexible. After a false start when they sold me a non-heavy duty coupling
that blew up, I have never had a moments trouble with the drive train.
Norm
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