In a message dated 5/9/03 11:00:34 AM, giles.morris(a)unisys.com writes:
>Not really about Montgomery boats, but there's a lot of knowledge out on
>this list, so I'll ask anyway.
I did several engine removal/replacements during my stint as boat mechanic.
Did a similar swap (less the new beds) on Friend's Flicka a couple of months
ago. The 1GM, at 160 lbs., is decidedly lighter than the 2GM (which is what
I suspect you have). Also replaced aluminum beds on a powerboat with two Cat
3208T diesels (engines in the thousands of pounds, and the size of small
cars!). Learned some important lessons with respect to alignment.
>Dolphin has an inboard diesel -- a 2-cylinder Yanmar weighing about 220
>pounds (according to the manual). The rubber engine mounts rest on two
>engine beds that look, in section, like inverted U shapes with a flange
>on one side for the mounts. The beds rest on stringers glassed into the hull.
>The beds are corroded badly enough that it's time to replace them, and
>ditto for the metal parts of the mounts. Luckily, there is a hatch in the
cockpit
>floor and access from the cabin is unobstructed and the whole width of
>the engine room. (Of course, if there wasn't a hatch the water wouldn't have
>leaked in to corrode the beds...). This means that I can get at the engine
>with relative ease.
The Flicka also has a removable cockpit sole hatch. The owner special
ordered a thick/wide rubber material that we installed. I am now in the
habit of spraying mounts with a product called 'LPS-3'. It is a spray
coating that dries to a thick, waxy film. I have sprayed several outdoor
items (in full exposure), and have found it does wonders in preventing
corrosion.
>Here's my plan:
>
>Disconnect the prop shaft flange, fuel pipes, exhaust, water inlet,
>electrical connections and control cables. Remove the bolts that hold the
>engine mounts to the beds and slide the whole thing (engine, transmission
>and old mounts) forward and then down (about 6 inches) onto the cabin floor
>(suitably protected with a piece of plywood.
Maybe place a blanket or piece of carpet under the plywood to protect your
cabin sole.
> Given that the engine weighs about the same as a well-fed human, I'm
thinking that with one helper I can do this without rigging up a hoist that
would have to allow it to swing forward.
I know this is not a problem with the 1GM (we did the same thing). You might
want to rig a safety tether from the boom, down the companionway hatch, and
to one or both of the Yanmar lifting loops (I seem to remember two--one
forward, and one aft) just in case it gets away from you. I use a nylon
choke strap (tow strap) around the boom, and then rope(s) to carabiners on
the engine loops. I then run the main halyard to the top of the choke strap
so that I am not loading the center of the boom unduly.
>A local sheet metal company say that they can duplicate the beds for me
>in stainless steel (don't want to do this again) and the new mounts are
already
>waiting in the garage. Put the new mounts on the new beds (I line them
>up with holes drilled in a plywood template that matches the engine), get
>the helper back. Lift, slide, wrench (bolts, not back), reconnect, align.
Start
>engine.
>
>What could possibly go wrong?
We had a little trouble when the person standing in the cockpit hole
(lifting/supporting the aft part of the engine/transmission) tried to help
with the moving forward and setting down of the engine below (he couldn't
reach far enough through the forward opening without breaking his back, and I
had to absorb the entire weight of the engine/transmission while standing
below). With the 2GM, it would be that much harder to make the transition.
I think in retrospect, it would have been easier if we had made a plywood box
that, when placed on cockpit sole, would have resulted in a platform height
equal to that of the engine bed. This way, we could have 'slid' (wobbled) the
engine all the way forward and out without worrying about the 'down' part.
If you have access to the underside of the beds, I would put mounts on
engine, and not bed. It will be easier to slide in atop bed than to try and
lift engine over vertical mount bolts. Use nylock nuts on the underside of
the mounts (engine mount to bed) I don't need to tell you that these engines
vibrate!).
Take this opportunity to check/decarbon/desalt your exhaust elbow. They are
notorious for loading-up. It is also a good time to change the zinc (you
didn't say whether yours was a raw of fresh water cooling variant), any hoses
that look suspect, your secondary fuel filter (use new copper crush washer),
and anything else that is going to be easier to get to while the engine is
out.
Alignment: After having witnessed several premature engine mount failures, I
have devised a new method for aligning engines. It is just too easy to load
the mounts with all kind of bizarre forces doing it the way the books say to
(in other words, raising or lowering one mount--even if you make a
commensurate adjustment the adjacent mount, can still result in a kind of
tension-compression thing that goes undetected.
Here is what I now do.
1) Set engine on mounts with *all* mount nuts/bolts loose (including those
through the bed and the top nut.
2) Pull the shaft flange forward so that it is maybe 1/8" from the
transmission flange. Rotate the shaft and/or transmission to make sure that
neither has any excessive runout (eccentric movement that would suggest a
bent shaft or other malady).
3) Make sure engine is nearly level laterally (in other words, is not tilted
to port or starboard--this is one of the most common mistakes people/shops
make). I use a torpedo level across the top of the head (I first take a
reference reading on some known level part of the boat just in case the boat
is listing, and adjust weight to bring boat into normal lateral trim). I
like to start with all of the mounts at the same height (that is, the bottom
nut/washer on the vertical shaft is the same distance from the base of the
mount). Any adjustments I make are in quarter turn increments, and I keep
track of each adjustment.
The primary difference in my approach here is that I laterally level the rear
pair *first* by having someone/something lift the front of the engine off of
the mounts entirely (lift at the center of the front of the engine). This
way, the weight is distributed equally across the rear mounts, and any given
adjustment only tilts the engine from one side to the other (not doing this
is what results in a weird twist dynamic resulting from the front mounts
interfering with equalization of the rears, and the result is that you end up
overadjusting them to try and establish level--this is where undo compression
or tension results).
When I have the rear leveled and equalized, I have the helper lower the front
slowly until the engine just contacts one or both of the mounts (one is
almost always a little higher or lower than the other) just touches it (not
loading it). I have him/her/my block hold the front of the engine in just
that position while I move the bottom adjusting nut up on the mount that is
not making full contact with engine. We repeat the above lifting and slow
lowering until the engine just touches the mounts equally. You have now
leveled the engine laterally.
This process is the only way I know to establish a level engine plane that
loads all of the mounts equally (or as equally as possible given the weight
distribution). Uneven loading is probably the primary cause of premature
failure, and it doesn't take much 'tighten a little here and loosen a little
there' to really put some eccentric loads on these mounts.
Don't worry that the engine is not aligned to the flange--we will take care
of that next.
4) Do a rough lateral alignment of engine so that gap between both flanges is
equal, and that the outer edges are flush/line-up. Make sure that in so
doing, that none of the mounts are twisted (out of plumb). If they are, the
engine will merely 'spring' back to its previously unaligned position. Also
make sure that the bolts securing the mounts to the bed are as close to the
center of the oval holes as possible (as opposed to all the way forward, aft,
or port starboard in the hole). This will ensure that you can make subtle
adjustments later. When you have equal lateral gaps at the flanges, and the
outside rims of the flanges are flush/alligned, snug (but don't torque) the
mount-to-bed bolts/nuts.
5) I start the vertical adjustment at the rear mounts. I slide the shaft
forward so that the two flanges just touch. First, I check that the outside
of the flanges line up (or in the case of unequal sized flanges, that the
difference is equal top to bottom). Next I look at the gap between the
flanges top and bottom.
Given that we have already established lateral level and alignment, we are
now looking to adjust two things:
a) vertical height of entire engine
b) longitudinal tilt of entire engine
I find it useful to do (b) first. By looking at your feeler gauge, you can
determine whether the engine needs to be tilted forward or aft. Don't worry
about the alignment of the outside edges of the flange right now--we just
want to have the same gap between flanges at the top and bottom.
Adjust this gap *only* by adjusting one pair at a time (front or rear) of
mounts exactly equally (one quarter turn port, one quarter starboard--keep
track!). Check each adjustment with feeler gauge until you arrive at either
no gap, or equal gap (if you have equal gap rather than no gap, the lateral
alignment is still off a little). When you arrive at this point, the flange
planes are aligned, but we still have to adjust the flanges so that outsides
are aligned.
6) Aligning so that the two flanges are lined-up is now a simple matter of
raising or lowering the entire engine plane equally (we have already set the
vertical flange planes in the previous step). This is done with exact equal
changes at all four adjustment (bottom on the shaft) nuts (again, I use
quarter turn increments, and keep track of them). Assuming no runout, you
are done with this step when flanges are flush or at least equal (if differen
t size).
7) You should now have something approaching zero clearance (Yanmar has
allowable tolerances in the manual) at each of the cardinal points around the
flanges. If you still have some lateral clearance, you can usually adjust
this without affecting all of your leveling/vertical work by loosening the
mount-to-bed bolts and carefully/incrementally moving the engine. A good
final test is that the bolts that couple the two flanges should now engage
without struggle or having to lift, jerk, or otherwise manipulate your engine
or the shaft.
8) When all is good, I do one final check of level/loading by sliding the
shaft/coupling flange aft, and repeating my level test of the rear and then
the front mounts (step #3 above--this assures that you didn't do anything
screwy when you were counting your turns!). When I am satisfied, I torque
all of the mounts appropriately. A jamb nut on top of the securing nut is a
good idea--the Yanmars like to shake them loose.
9) If all of this wasn't enough, you are going to want to check your
alignment several times following the installation of the new mounts. They
*wiil* settle-in (compress) gradually for quite some time. Failure to
check/readjust can wear your cutlass bearing, and even worse, result in
loading of your transmission output shaft bearing. Besides, just think how
good you will be at this after doing several times. I would check after the
first ten hours of engine use.
>If anybody has experience with doing something like this, I'd be most
>grateful if you could let me know what you wish that you'd known before
>starting. If you see what I mean.
>
>Giles Morris
>M-15 Umiaq
>Vancouver 25 Dolphin
Sorry for the volume of stuff here. You already know that I am not a person
of few words! Hope some of it helps.
Scott Grometer, M15 #478 'bebe'
