How to Assemble a Flex Cable and
First let me say assembling your own flex cable
and prop shaft is a great way to save some money. There are a couple
of methods used to attach the prop shaft to the flex cable. The
Soldering method which Octura recommends is outlined in directions
that come with Octura parts. But I feel the soldering method is
harder and more prone to error than the way I'm going to outline in
this article. We use the glue method.
Here are the items you will need.
Flex cable and prop shaft. Most Fast Electrics use
left lay flex cable. A good rule of thumb is for 6-16
cells use a .130 cable. For 17 cells to 24 use a .150
cable. Most boats are using a 3/16" prop shaft. Smaller
boats may want to use a 1/8" prop shaft.
A sleeve retainer type glue. We use and sell
Loctite 603 but some people suggest Permatex High
Strength Sleeve Retainer. The Permatex is a bit easier
to buy at your local auto parts stores. I have never
tried the Permatex. So I can't comment on its strength.
A piece of medium sandpaper
A dremel tool or drill
A sharp 1/16" or similar drill bit.
Rubbing Alcohol and a rag.
First take a look in the end of the prop shaft and remove any loose
filings left behind when it was drilled by the manufacturer. Just
tap it on your bench upside down a few times.
Next we are going to measure how much of the flex
cable fits into the prop shaft hole. We are going to lightly sand
that part of the flex cable. This will help give the glue a better
bite on the flex cable and remove the plating, like in the below
picture. After this is done take your rag with alcohol on it and
wipe down the end of the sanded flex shaft. This will help remove
the oils and fillings. Set the flex aside to dry off completely.
Next to help the glue bite to the inside walls of
the prop shaft hole we are going to "nick" the inside walls of the
hole. This is done easily with the drill bit by sliding up and down
at an angle at a slow to medium speed on your dremel tool. Try to
nick up most of the area inside the hole. Take care to not drill to
much. It should take no longer than 30 seconds to do this. Than tap
it on your bench again to remove the fillings inside. If you don't
have any fillings come out, there can be a few reasons. You didn't
have a sharp enough drill bit and the process needs to be done
again. Or it could be that when the original prop shaft hole was
drilled the manufacturer could have left behind some cutting oil
which the fillings are binding to.
Now we have to thoroughly clean the inside of the
prop shaft. We first need to tightly twist/wrap a piece of paper to
a size that's a bit larger than the prop shaft hole. We use the
scrap octura packing that comes with the flex cable for this. Than
dunk the paper in to rubbing alcohol.
Now twist the paper inside the hole. Keep twisting a few times than
remove the paper. You should seen some of the filings and cutting
oils. Repeat with a new piece until when you remove it, the paper is
nice and clean. Once clean insert a dry piece and twist. Once its
removed in should come out as clean as it went in.
After the first pass you can see the tip is brown from the cutting
Now that we're done prepping the parts its time
to start gluing it all together. We are now going to coat the inside
of the prop shaft hole first. The Loctite 603 is so thick that it
won't flow inside the hole on its own. I use scrap ends of plastic
tie wraps to push the glue inside the hole and rub it on the inside
walls making sure to cover all the entire area.
Next make sure the flex is dry by wiping it with
a clean rag. No grease should be on the rag. If there is grease
showing on the rag clean the shaft again with alcohol. Than use the
glue to cover the part of the flex shaft that will be in the prop
Next we are going to assemble the two pieces.
This is the easy part. Just slowly push the flex into the hole and
twist it a bit. Some glue will come out. Just wipe it with a clean
Allow it to dry a day or so before use.
Shaft and Cable Glued and Ready for adjustment.
Final adjustments to the Flex Assembly.
First install the drive dog where you want it on the shaft. To
find this area select the largest prop you will use on the shaft.
Try it on the shaft with the prop nut or bullet nut. Once you know
where you want the drive dog to go, mark the area by tightening the
grub screw a bit. Than loosen the grub screw and remove the drive
dog. There should be a small nick/mark on the prop shaft where the
grub screw was tightened onto the shaft. At this location on the
prop shaft make a small flat spot with a file or dremel tool with a
sanding disk. Now put the drive dog back on and tighten the grub
screw, making sure the screw is tightening on the flat spot. If you
want a more permanent drive dog you can use the retaining glue to
help secure the dog to this area. Just apply the glue on the shaft
and slide the drive dog on. Than tighten the grub screw. This will
help insure the drive dog doesn't slip under the heavy prop loads.
Next its time to make the final cut to the cable.
Measure the total length needed and add 3mm for the space needed
between the drive dog and the end of your strut.
Remember the cable can be shortened, but not lengthened. So cut the
cable a bit longer than you may need and shorten to adjust. Once you
have made the final cut, roughly sand the last 1" of the cable end.
Than use a soldering iron to solder the last 1/2" of cable solid.
This will help stop the cable from unraveling under heavy loads.