How To Install a Stuffing Tube in
a RRH Mutineer Mono.
written by Paul Pachmayer of
Installing a stuffing tube in any boat is very important
part of your building process. Done correctly your rewarded with a
free running drive line with the least amount of friction thus
maximizing your motors potential. Also included in this "how too" is
my modification of a Warehouse Hobbies strut (now available from
Fine Design Marine). These struts were designed to use a 1/8" stub
shaft and .098 flex cable which really isn't suited to higher
powered motors we have today. What we want is to run a .130 flex
cable and 3/16" shaft so a new bearing cartridge is in order, this
is an easy modification and I'll show you how I do it.
One thing to keep in mind is I don't use Teflon tubing in
my drive lines. My opinion is that a straight brass stuffing tube
has less friction than Teflon tube. Try it yourself, put a piece of
flex cable in a Teflon tube and spin it. Notice the rotations and
try it again in a piece of 3/16"OD brass tube. Which one seemed to
have less resistance? Another bonus to straight brass tubing is that
it's much easier to keep water from entering the hull, later in this
"how too" you'll see exactly why.
First thing to do is locate where the stuffing tube hole
in the transom should be. For monos my general rule is 1/8" up from
the chine. Some people like offsetting this location to the right on
monos, the theory is that the offset helps counteract prop walk. I
like running mine centered, not that it's better, it's just my
personal choice. Make your first mark 1/8" up from the chine, from
that mark measure up another 3/16" and mark that location. Between
these two marks is where you will drill your stuffing tube hole.
After you mark these locations it's time to install the strut mount
to the transom.
Take the strut bracket and place it on the transom so the
two marks you made are centered in the lowest hole on the bracket.
Now you want to mark the location of the lower bolt hole, take your
time and make sure your stuffing tube marks are centered and that
the bracket sides are straight up and down. Once your satisfied with
the bracket placement make your mark in the center of the LOWER bolt
hole. Now drill a 3/32" hole. Mount the bracket with one of the
countersunk 4/40 bolts in the hole you just drilled. Now check that
the bracket is straight up and down on the transom and drill the
upper bolt hole and install the other bolt.
Now that the bracket is installed drill the 3/16" hole for
the stuffing tube in the center of the marks you made earlier. When
your done it should look like this.
Now it's time to prepare a piece of
3/16"OD K&S brass tubing for the stuffing tube. First thing to do is
anneal the tubing so it's easier to bend. Annealing is simply
heating the brass tube until its glowing red. I use a propane torch
to do this which works very well. The stuffing tube is about 3 5/8"
long for this boat and I anneal all but the last 1/2" at each end.
Now you want to make the bend in the
stuffing tube to match the angle of the motor. Install a motor with
coupler to the motor mount and place it in the boat. If you use an
Octura Flex Hex like I am be sure to remove the nut that tightens
the collet. I use a short piece of left over flex shaft in the
coupler to get a rough idea of what the down angle of the motor is.
Gently bend the stuffing tube so that the flex shaft fits
right down the center of it. Ideally you want as little bend in the
tube as possible, in other words as close to a straight shot out the
back the better. Notice in the picture that the flex shaft runs
straight down the center of the stuffing tube and that there is
about 3/8" of flex showing between the stuffing tube and coupler.
Now it's time to build the new
bearing cartridge for the strut. There's 2 ways to do this and both
work equally as well. You'll need 1/4"OD and 7/32"OD K&S brass
tubing, a piece of Dave Brown FG push rod tube and a Octura 3/16"ID
For this install I made the bearing
cartridge the same length as the original that came with the strut,
you can make them longer or shorter to personal preference. Cut a
piece of the FG pushrod tube 3/4" long. Take the lead/Teflon bearing
and slide it into the end of FG tube.
Now slide the 1/4" brass tube
into the FG tube until it touches the bearing. Cut the 1/4" brass
tube 3/8" away from the FG tube. After you cut the brass tube apply
a drop of thin CA at the edge of the FG tube to secure them
together. Now take the 7/32" brass tube and slide it inside the 1/4"
one until it touches the bearing and cut it flush with the end of
the 1/4" tube. Again, apply a drop of CA to the seam of the two
brass tubes to secure them together. It's helpful to lightly sand
the outside of both brass tubes before assembly so that the CA gets
A shot of the stuffing tube,
strut, original bearing cartridge and home made bearing cartridge.
The other way to build the
bearing cartridge is to use the brass tubing as your bearing surface
rather than the Octura lead/Teflon bearing. In this instance you
would just use all brass tubes nested inside one another all the way
to the end of the FG tube. You could also use brass tube instead of
the FG tube, just be sure you end up with an OD the same as the
OK, now we will assemble the whole thing and fix it in
the hull. With the stuffing tube in the hull install the strut on
You'll notice that the stuffing tube is
hanging out of the back of the strut. You want at least a 1/2" of
the stuffing tube showing, this will be positioned correctly in the
next step. Take the new bearing cartridge and slide it into the
strut housing, don't be concerned if the stuffing tube is resting
inside the lead/Teflon bearing. Now take your stub shaft and slide
it into the bearing cartridge.
The step on the Hughey stub shaft is resting against the
stuffing tube. These couple of pictures show what's going on inside
the bearing cartridge. The first picture shows the turned down area
of the stub going into the stuffing tube, the second picture shows
the stub bottomed out against the stuffing tube.
Now you just push the stub into the
bearing cartridge until it can't go any further. You just set the
depth of the stuffing tube and are finished with this part of the
install. The nice thing about this setup is the stuffing tube is
aligned by nature because it nests inside the brass tubing in the
bearing cartridge, it also acts as an additional bearing support for
the front of the stub shaft.
One other thing of mention, because the
front of your stub shaft rides in the stuffing tube there's no gap
for water entry!
Now we move to the inside of the boat to fix the stuffing
tube in place permanently. Check to make sure the flex shaft is
still running down the center of the stuffing tube and make any
necessary adjustment. It should look like this.
When your satisfied everything is
aligned put a few drops of thin CA around the stuffing tube at the
inside of the transom. This will hold everything in place and seal
the hole you drilled for the stuffing tube. Now we epoxy the
stuffing tube in the hull. I personally use an epoxy called Plastic
Bonder from Power Poxy. This stuff gets nice and hard and sets in
3-4 minutes, it also doesn't get brittle like normal epoxy. I find
myself using the Plastic Bonder on just about everything because it
doesn't self level, in other words it stays where you put it. Mix
some up and apply it to the area where the stuffing tube enters the
inside of the hull and at the same time fill the area under the
stuffing tube to support it.
That's it! Now you have a nice free
running drive line. The only other thing I do is put a small piece
of silicon tubing on the inside end of the stuffing tube to help
keep out any water that may make it up the tube. You just need a
small bit of the silicon tubing touching the flex shaft to do the
job, too much touching just creates drag on the flex. Here's a shot
to give you an idea of how much should be touching.
This procedure is the same one I use
on all the monos I build, the stuffing tubes last the life of the
model and require little maintenance. I think once you try it you'll
be quite pleased with the results. I hope this has helped you some
in understanding how to install a stuffing tube in your own boats.