Not necessarily a problem, if you know somebody who is competent with
a lathe.

"Edgar" wrote:
You need more than that and in the end you will not have saved much if
anything compared to a new shaft. You cannot just rduce the worn area in
diameter because you will need smaller bearings and stuffing box and then
you will not be able to pass the rest of the shaft through such bearings
etc.

If you have to reduce the shaft by a size increment, yes. If it just
needs to smoothed out by a couple thousandths, then it's no big
deal.... more than you can accomplish on a bench with emery paper,
though




The usual way to reclaim a shaft is to turn down the worn area and build
back up with sprayed-on metal and remachine to the original size. Metal
spraying is a well established procedure but is dependent on the skill of
the operator and although it looks OK from the outside when finished I am
always suspicious about the adhesion.

Same here, especially under a heavy torque load.


A thrust bearing would be a better investment, that way the alignment
of the shaft is not as critical and any shock put on the drive system
will not be carried to the trnasmission & engine. They are expensive
and take up room and require some engineering, though.... which is why
they are far less common!

"Edgar" wrote:
The alignment of the shaft is always critical unless flexible couplings are
involved and this is very expensive.

Yep.... that's what I said.

I have seen a few pleasure boats with thrust bearings installed...
it's great, makes the boat much quieter & smoother running.


There always has to be a thrust bearing and it is normally an integral part
of the gearbox except for larger vessels


Correct. But IMHO it doesn't do the tranny or engine any good at all
to use them as the thrust bearing. Especially in a boat that is
maneuvering a lot with heavy reversing loads.


(snipped) We stayed briefly at a marina
that had a racket in new shafts.... he had a warehouse full of old
shafts that he polished up & reinstalled in boats that hit rocks...

Probably not a racket. Someone replaces a 10' shaft and allows him to keep
it and he just holds onto it until someone comes up wanting a shaft that is
shorter. Then he just cuts off the worn bit and machines up a new shaft.
Seahags 10' shaft is a valuable piece of steel or bronze bar and she should
ensure that its value as such is taken off her invoice for the new one!


Depends a lot on whether the shaft really needed replacing, doesn't
it? However I am very slow to accuse anyone of this sort of thing,
since I do not have the proper tools to evaluate the situation
myself.... however, out of the several boats passing thru the area
that had work done at this marina, 3 had shafts replaced and no
particularly good explanation given. Another boat at the same marina
wanted to get some electrical work done but rejected their offer to
simply replace battery bank & charge controller.... again with no good
explanation of why this was needed.... kinda raised an eyebrow,
y'know?

Fresh Breezes- Doug King