Well, actually I got
the instructions for this from Vance who posted them way back. Since doing my
own thrusters with those instructions, Greg Cottrell came over one
evening and we did his with the Vance method as well.
1. Take the motor
apart. You want the can with nothing else attached, because when you drill
holes in it there'll be chips, which should not be allowed into coils or
anywhere else.
2. The magnets are
glued to the can, so you can't remove those. Drill two holes on opposite sides
of the can, making sure you miss the magnets. Choose the hole location so that
once the thruster is installed, one hole will be at the motor's
highest point and the other at it's lowest.
3. Tap the holes and
install threaded plastic elbows for 3/8" clear vinyl hose.
4. Clean up the chips
and put the motor back together.
5. Connect about 6-8"
of vinyl hose to the lower elbow. Use a funnel to fill the motor with oil
through the hose until it flows out the top elbow.
6. Wrap the hose around
the motor (mine loops once around the shaft) and connect to the top elbow. You
want to do this trying to avoid air bubbles, which means you make the
connection quickly with oil flowing -- a puddle on the floor is unavoidable.
The hose has two
functions; it comes in handy for filling the motor, but more importantly it's
compressible. A tiny bit of air is unavoidable (barring a bathtub full of oil
to assemble the thruster submerged) so the flexibility of the hose keeps the
seal from being squeezed by compression of that remaining bubble.
That's it for oil compensation. Each motor should
take you about half an hour to do. The other question that comes up is what
kind of oil to use. I've used Marvel Mystery Oil and this time I just refilled
with WD-40.
Now as for sealing up
the cables, that depends on whether the motor shaft is going through the hull
or not. If it is not, as on my stern thruster, then you've not got any
significant pressure differential across the cable seal. I've just got that
one sealed with marine silicone around the cable jackets. But on the side
thrusters it's a whole different matter. Look at Emile's project, he's got a
photo showing really super workmanship on a trolling motor penetrator.
What you want to do is connect a section of solid conductor inline
with each cable, to prevent pressurized oil from wicking along the strands.
You have to pot those solid conductors with epoxy inside the thruster shaft.
The shaft should have a groove or thread on the inside to give the epoxy
something to hold onto. The tricky bit is the lack of space. You have to keep
those conductors apart so they don't short out, but also have to keep
them from touching the shaft wall. As you can see Emile did it with a
plastic insert that acts as a spacer. Be as generous as space affords with the
cable diameter -- you don't want to pot a space heater that melts
epoxy.
good
luck,
Alec
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Hi Alec. Could you explain in more detail how you switched over to the
oil compensation of your thrusters?
I remember the past thread and drilling a new hole in the thruster casing
was made for the addition of the oil.
How is the existing hole with the wires sealed up?
I found some brass compression fittings at the hardware store that the
threads on the Minnkota motors match, and the original supplier also had an
aluminum fitting with a rubber compression grommett that screwed into the
nipple where the wires exit the motor. What parts and methods have you got on
yours?
Frank D.