Hi, I'm Mark Corke from BoatU.S. Magazine. Welcome aboard. Today I'm going to walk
you through all the steps required to change out the shaft seal sometimes it's
called a shaft seal might be called a stuffing box but basically they're all
the same thing, it's where the shaft goes through the bottom of the boat and
there's a seal there which enables the shaft to rotate but actually keeps the
water out from the boat, So, on a traditional shaft seal, and I'll show it
to you once I've removed the old one, but I can't show you right now but once the
old ceiling is out you'll see that there's flat packing in there and the
Shelf rotates inside this flat packing and it's been in existence for hundreds
of years this design I basically started using it on windmills I understand but
there are alternatives to that and we're going to use this one which is called a
packless shaft seal and you'll notice that there is a clamp on this in two
clamps on this end this connects to the stern tube and then obviously on this
end we've got a special carbon bushing and what happens is that this part stays
stationary this part, which is the stainless steel rotor, clamps to the
shaft and it's machines so that it makes against that and it rotates and because
we put a preload onto this rubber bellows, in other words we squash it as
we connect the thing together, it pressured pressurizes this rotor so that
there's no water to come out. You'll also notice that there's a spicket here with a
hole in it on this boat we've got water injection so we've got water coming out
from the exhaust and there's a little bit of water goes down here as the
engine is running and that helps lubricate this bearing it won't leak but
it just helps lubricate it otherwise it would run dry and get very hot. But
anyway, so we're going to get started on this right now and I'm going to walk you
through all the steps required to do this it is one job that can also go very
quickly or it could take you a long time. The hardest part about this is often
getting the shaft from the coupling off the back of the gearbox that's often the
most difficult part what once we've done that we're good to go,
so let's get started.
So first things first, is to remove the two bolts that clamp the coupling to the
shaft. Every boat is slightly different and in what you're looking at on your
boat may not be exactly this, but there's a square headed bolt on this boat and
that fits into a dimple on the shaft and it's an extra security to prevent the
shaft turning inside the coupling so I'm going to go ahead and unscrew that one
now too.
So there's a dimple down in there and that allows me to get some oil down in
here to free up the joint here so I'm going to let that sit in there what I
undo the coupling bolts here too now these may be quite tight and what I've
done here is I've actually wedged a wrench in here to prevent the gearbox
from turning this is just preventing that from turning so I can get some
welly on the bolt so the bolts come out. And one thing I will tell you is that, if we can rotate this...
it rotates by hand I want to show you something in what I did before I started
it is I put a Sharpie mark next to this bolt hole and on to the coupling here so
that when it goes back it will go back in exactly the same place because if it
doesn't there's a chance that something will be out of balance we know that the
engine works perfectly fine now so if it was not right we would have a problem
with vibration. All you're going to do now is remove the rest of the bolts.
So I've pulled all the bolts out and you'll see that I've actually started to
separate the shaft from the coupling so what's happening is that now the shaft
is actually moving back in the in the boat but what I'm doing is I'm actually
putting some penetrating lubricant oil in the little square-headed bulb that we
took out earlier and that will creep around the shaft and enable me to get
the coupling off the shaft. I'm going to leave that for half an hour so just to
do its thing and then we'll slide the shaft further back out of the boat and
then we can start looking at kind of pull this coupling off the shaft. As I
said before, getting this coupling off the shaft is going to be the hardest
part of the job it nearly always is so we're just going to leave that now we'll
come back in a little bit. So I'm outside the boat now
and I'm just going to wiggle the propeller backwards and forwards I've
got a bit of leverage or leverage Americans say and slide this back so
that this will give me some space inside the back
and while this is pulled back it gives you an opportunity to examine the shaft
away because this is the cutless bearing here we've got a little bit of wear here
not too bad but at some point the shaft is going to need to be replaced but it's
got a few years yet so we need to worry about it just now I've removed all the
bolts obviously and I've given the penetrating oil a good hour to work the
coupling is what's called an interference fit onto the shaft so even
without any rust or corrosion or anything in there it should be a tight
fit so it shouldn't just fall off. Now what you must not do is hit this because
this is a casting if you hit this with a hammer
you're going to distort it or and or you're going to break it, so we've got to
be very careful about that. So I'm going to very carefully use a
puller, I've got a pullet here, and I'm going to
put this on here, tighten this up, and just very, very carefully tighten this up...
and I should be able to see it's just going to move so I'm going to do this a
little bit over time a little bit over time can't overdo it because if I
tighten this up too much I'm going to distort something I'm going to break
something so you're going to be patient with this and let science do its thing
so a little bit more oil bit of waiting let it go and we'll persevere and we'll
get it off. Persistence has paid off after about an
hour and a half, I've managed to slide this off just giving it gentle pressure with
the puller and actually liberal amounts of
of penetrating oil so that's come off. If you look in here now if you can see this
on the camera you can see the keyway which lines up with this brass key which
goes in a slot on the end of the shaft and that was the dimple or where the
square-headed bolt when in and all this is obviously going to be put back
together but now that we've got this off the thing to do next will be to unbolt
the original stuffing box, slide it up the shaft, get that off out the way, clean
the shaft up, and then we can start reassembling. So we've separated the
coupling from the engine and we just got the plain shaft here. Next stage is to
take off the old stuffing box here, it's really tricky to get to because it's
actually wedged underneath the generator, it's underneath the generator in the boat,
so I've got limited space here there's a board that you can just hear me
hitting it, tap that. So to make this easier the first thing is to unscrew these
bolts I just loosened them a minute ago we'll take this off. We can separate the
packing nut and then we'll slide this up and it will help it take it apart.
After a long struggle I've managed to get the old stuffing box out and I'm just
showing you this now so you can see how this is constructed. It is a heavy bit of
bronze and the component is that there is a compression washer, which goes on
the end here, that goes down in there and then I took that apart but inside
there's flax packing like this so when that's in there the shaft obviously
comes through the center and then this goes on
and he's bolted down with the nuts. And what that does is that that squeezes
this flat packing onto the shaft and makes a watertight seal. The only thing
is, with these type of packing is they're actually intended to leak slightly very
little so as I mentioned earlier we don't really want that, it's not
desirable, so what we're doing instead is we'll go back to this and you can
compare the two so this was the old this connected to a piece of rubber hose like
that with some closed clamps on it and then this end clamped onto the stern
tube, so because the rubbers there we've got a look we've got a little bit of
allowance for vibration and then obviously with this new one this
essentially replaces the rubber hose onto the stern tube and then this shaft
obviously comes out here and then the rotor will go on the front there so it's
a nice neat arrangement. It's a lot lighter than the old one that's made out
of solid bronze, this is much much lighter so not that it really makes much difference
but it will be nice to get this in and have a nice leak free boat. So what I've
got to do now is get back in the engine room, clean up the shaft, make sure
there's no sharp edges so that we can slide this on and slide the rotor on without
doing any damage. So let's get on and do that. There were some scratches here from
before, this wasn't something I did, somebody's worked on the shaft
previously and they put a pair of vise grips or something on here and there's a
few scuff marks, so they're getting smooth now. I'm going to take those
out just to make sure that everything is nice and smooth so that when we slip the
new rotor down there and the seal, it won't catch on anything and tear it
up so take the time to do this correctly.
So I've got the first half of the bellows on with the carbon ring on, the one
I showed you earlier. We've cleaned the shaft so there's no sharp pieces on here now and
what I'm going to do now is just lubricate the shaft with a bit of
dishwashing liquid we'll just put that on there and the instructions that come
with the seal expressly tell you not to use any kind of grease or silicone or
anything like that because it will destroy the o-rings inside the rotor and
I think you can see there's the o-rings in there there's one on each side. So
this just lubricates it a little bit and it's quite a tight fit once we get
started we get over those two o-rings you should be good so start to slide
down now you can see it shimmying down. The instructions actually tell you
to put the two set screws in here, the locking set screws in here, early on. I've
done this before they don't really make any difference but I'm actually going to
wait till later because this gives me the opportunity, if I need to, to actually
dribble a bit of dishwashing they put down the hole just to make sure that it
contacts the shaft. It's got a lovely smell and apparently it's good for your
hand. Okay, so I'm going to go ahead now and keep wiggling this on. Now that
we're well clear of the end of the shaft I'm going to leave it here for now and
we can go back and actually start to reattach the shaft to the transmission.
So this is just the reversal of what we did earlier, so now I've got to clean
this up a little bit and then I put the key back in here, and then we've got to
slide this back on here, so I'll get on and do that now.
So now we're starting to put things back together you'll see that the coupling is
back on the shaft because you've got to put the bolts in, the square-headed bolt.
I've already checked down there to make sure that the hole here lines up with a
dimple in the shaft it does I can't show you that on camera but I've shined a
flashlight down there to make sure it works. We've got we've got a gap here
we've still got to slide the shaft forward but I'll do that after I put the
bolts in and you can still just see there's a black mark here on the drive
saver and the black mark here still just visible which is the sharpie marker put
there to make sure that these two pieces line up correctly and go back in the
same position as they were earlier. So now everything's all nice and snug, you'll notice I put the four bolts here
which connect the propeller shaft coupling to the drive saver this is a rubber or hard plastic type of insulator
between the output on the transmission and the propeller shaft. The reason you
have that is it just gives a little bit of cushion between the engine and the
propeller shaft and it stops some of that vibration. Because we have that on
this boat, we also have to have this green jumper wire which gives us
continuous ground from the propeller shaft to the output on the transmission.
If we didn't have the plastic drive sizer, which obviously also gives you
electrical insulation between the propeller shaft and the engine, because
we want to ground we want to make sure that this is in place, which it is and
it's in good condition. We're almost complete now the last thing is this is
the rotor obviously that we fitted earlier and it has to be locked onto the
shaft and to do that the manufacturer supplies us with two tapped holes at 90
degrees to each other and we put these set screws in we're going to whine them
all the way in here and I'll show you why in a minute
we put one in and then we'll get another, they supply fout of these in a little packet.
We put a little bit of thread locker on there, which also comes in there, it's
blue, and then we'll screw this one in too So it just screws in, but don't screw it up to
the shaft just yet. I put some yellow tape on the shaft to show when
the rotor was at rest it was just resting against that carbon
ring which is behind it and then what I've done is I've compressed that now an
inch, in other words I've moved the ring the rotor back an inch from the edge of
this tape. There we are, connecting up the water injection hose was the last piece
of the puzzle. So there you have it. It took me about a day, but it was time well
spent. I've got rid of the old-fashioned stuffing
box now which used to leak, I won't have that pool of water and a bottom of
the boat anymore and, on top of that, I'll have less maintenance so I don't have to
replace the packing anymore. So I'm really looking forward to getting the
boat back in the water and we'll make sure that everything is good. For this
and for more projects please go to BoatUS.com/magazine