Hi, Roger, and group,

Thanks again for knowledgeable insight, left below and in the prior post.

Fortunately, in our boat, access is very open, so squirming around isn't an
issue - but it's what drives the suspended length.

I'm not going to be back on the boat for a couple of weeks, but when I am,
I'll pull the hose from the tube and do as you suggest about shimming and
see what the result is for the flange end.

I'll also check the length. I don't think it's 50 inches, but I'd be
surprised if it weren't more than 36.

And, you're correct. I cleaned up the faces with the rotary cup brush on a
grinder as shown in one of the pix. Not a milled surface, but pretty well
cleaned of rust lumps. Unfortunately, I don't have a dial gauge - though I
suppose I could find one to borrow. I painfully see your point about the
faces of the flanges - but don't know whether I feel it worth pulling both
of them out (the end of the shaft would be challenging, as I'm pretty sure
it's seized; the tranny would just be a nuisance, as I'd take the plate with
it off to some machine shop).

Hm. Without the shaft being in it, the shaft plate suffers the potential to
move from dead flush by virtue of the split end clamping. That gets into
some major work to attempt to ascertain (which would allow correction, of
course, but then would have to be disassembled again to reinstall - I guess
the trick would be multiple mount/dismounts at the shop to be sure it stayed
that way when reattached?) what flush is on that assembly.

Heh. The drive saver is looking more attractive just from a slop
perspective, though I'm still going to use the solid biscuit...

Thanks again.

L8R

Skip

Morgan 461 #2
SV Flying Pig KI4MPC
http://tinyurl.com/384p2 The vessel as Tehamana, as we bought her

"Believe me, my young friend, there is *nothing*-absolutely nothing-half so
much worth doing as simply messing, messing-about-in-boats; messing about in
boats-or *with* boats.
In or out of 'em, it doesn't matter. Nothing seems really to matter, that's
the charm of it.
Whether you get away, or whether you don't; whether you arrive at your
destination or whether you reach somewhere else, or whether you never get
anywhere at all, you're always busy, and you never do anything in
particular; and when you've done it there's always something else to do, and
you can do it if you like, but you'd much better not."

----- Original Message -----
From: "Roger Long"
Newsgroups: rec.boats.cruising,rec.boats.building
Sent: Sunday, April 02, 2006 4:21 PM
Subject: Drive alignment (was) Drive Saver/Spacer users sought


Skip,

Thinking about it some more, there is a lot to be said from the practical
side from fixing it solidly in the stern tube. With all the squirming
around in tight space, you're less likely to bump it out of the desired
line. Weighing the shaft also would then align it with minimal sag. (Use
the length from the wedges or split bushing in the stern tube for the
calculation.) If you are up around or over 40 shaft diameters of
unsupported length, this could make a detectable difference, but only if
you had two absolutely identical boats and listened carefully. Since
you'll never know, may as well cover the bases.

--

Roger Long



"Roger Long" wrote in message
...
The key thing is where and how you support the shaft. If it is a single
strut bearing system, you would like to have it end up centered in the
tube the flexible box hose attaches to in order not to have any preset on
the hose and maximize the possible movement in all directions. One way
to do that would be put wedges or a bushing in the stern tube. You would
then have three feet of shaft sticking out with a coupling on the end and
I would say, yes, you should weight it.

Simpler would just be to support it at the coupling and adjust for equal
spacing in the stern tube. The shaft will sag some small amount but this
will not be significant to the flexible stuffing box in the way that the
coupling face angle error would be with the overhanging shaft bending
down.

Speaking of the angles, do you have a dial gauge? It looks from the
pictures like the faces were cleaned up a lot. Unless the transmission
coupling was checked in the shop, you should set up a dial gauge and turn
it by hand to be sure it is truly square. The coupling style you have
makes this a pain to do as you have to be careful not to knock the whole
thing out of its base setting as it skips over the cut outs. You want to
also check the shaft the same way. This is hard in the boat because the
bearings make it want to "screw" for and aft as you turn it, even if the
helper manages not to push for and aft on the prop.

The whole idea is to get the geometry such that, if the shaft was
weightless and just sticking off the end of the engine, the center at the
prop nut end would not be going around in a little circle as the shaft
turned. As the engine moves around on its mounts there will be larger
misalignments and flexing in the whole system. However, if the shaft is
attached at even a slight angle, the engine will be trying to wave the
whole thing around in that circle. Since this happens on every
revolution it is rhythmic and sets up impulses that something will
resonate to and you have vibration.

How many shaft diameters do you have between the coupling and the shaft
bearing? Might be better to look for any red flags now than after it is
all together.

--

Roger Long



"Skip Gundlach" skipgundlach at gmail dotcom wrote in message
...
Hi, Roger, and thanks for the response, left below.

The shaft in the M46 is pretty long. I've not measured it, but I'm
guessing 7-8 feet minimum.

The stuffing box is on a hose, which is flexible; there's a tube from
the stuffing box, through the hull, and out to the cutlass. The last few
inches of the cutlass are cut away ~45* to half coverage, making a water
vent, and the tube is kerf-width slit in a couple of places on the
bottom, between the keel and the Pstrut for about 20* or so for more
water lubrication.

So, I'm reasonably sure there's not an intermediate bearing; there had
been one, not far before the stuffing box, but it was removed,
presumably when the SS shaft (stiffer, I'd assume) replaced the Bronze
original.

However, there's lots of length between the stuffing box and the
tranny - 3' or more, I'd say. Does that impact your advice (for which
I'm grateful)?

Thanks.

--
L8R

Skip

Morgan 461 #2
SV Flying Pig KI4MPC
http://tinyurl.com/384p2 The vessel as Tehamana, as we bought her

"Believe me, my young friend, there is *nothing*-absolutely nothing-half
so much worth doing as simply messing, messing-about-in-boats; messing
about in boats-or *with* boats.
In or out of 'em, it doesn't matter. Nothing seems really to matter,
that's the charm of it.
Whether you get away, or whether you don't; whether you arrive at your
destination or whether you reach somewhere else, or whether you never
get anywhere at all, you're always busy, and you never do anything in
particular; and when you've done it there's always something else to do,
and you can do it if you like, but you'd much better not."

"Roger Long" wrote in message
...
If you just have a single shaft bearing, just ahead of the prop, you
don't need to weigh the shaft. Just suspend it so it is centered as
closely as possible in the stern tube. Be sure to hang and fix it by
the coupling or close to it. Some stuffing boxes also incorporate a
bearing so check carefully. If there is a bearing in the stuffing box,
it's a bearing. If your stuffing box isn't flexible, there probably is
a bearing in there somewhere.

If you have two bearings, measure the length and diameter from the
forward shaft end to the bearing and calculate the volume and weight
(.28 lbs / cubic inch is close enough). Divide by 2. Then calculate
the volume and weight of the coupling. Add the two weights. Hang the
coupling so a pull scale inserted in the wire reads this amount. You
will then not be lining up to a shaft that is drooping under it's own
weight.

On further reflection: shafts in most sailboats are probably so short
that this isn't a big issue. On power boats, there will often be
several feet of shaft between the bearing and the gear. Still, it
wouldn't hurt to hang and weight it. We're talking about very small
tolerances here.

--

Roger Long

If you used a grinder on those coupling faces, I would strongly advise
pulling the shaft and having at least that coupling trued up. At the
same
time, they can check for straightness, wear that will shorten bearing
life,
prop taper fit, etc. Straightness is a greatly overlooked issue,
especially
in the long shafts that many pleasure boats have. The offcenter mass
in the
middle pulls the shaft out of line which puts the mass farther from
the axis
of rotation. The result is many pounds of steel spinning off center.
It's
tough on your rear end, your ears, and all the bearings in the system.
It
can also work your flexible stuffing box overtime.

The transmission is a tougher matter but the fit on the shaft is apt
to be
better than the prop shaft since it was presumably done at the
factory. I
would pull that coupling and have them do what they can with it. You
might
also look into buying one that fits and is full round so you can align
and
check it more easily. Buy or rent a dial gauge and check it in the
boat
after reassembly.

It's always painful to insert a major project like this into the
schedule at
this stage but you are going to spend many hours listening to that
engine.
Vibration increases fatigue and weakens components in other systems.
If it
isn't smooth, it's going to cost much more time and money to fix it
later.

You don't have a thrust bearing so you can't put in anything soft
enough to
accommodate any real misalignment. A Drivesaver will mitigate but
it's only
going to take the edge off the kind of problems you could have in that
coupling.

Friend of mine has the identical boat. With the same kind of prop,
his
vibrates like crazy while mine is smooth. I haven't touched my
shaftline
yet so it's just luck but it does show that subtle things can have
large
effects. He has a Drivesafer too.

Sound like you are going to be sailing off over the horizon. You are
really
going to be depending on that engine. This is the time to be sure the
shaftline is right.

--

Roger Long