cross posted to rec.boats.electronics

hi all,
im hoping to install a trolling motor on a 14 foot beach cat, for those
interested, a local australian design the 'caper cat'. There is plenty of
reserve bouyancy and ctorage space in the hulls. The rough plan is to go
with two 75Ah AGM gel cel batteries, one in each hull. The batteries are
totally sealed and can be mounted upright, sideways or upside down, so im
not too worried about flying a hull. Ill need to mout the batteries somehow
in the hulls so they dont come lose and damage the boat.

im going with a trolling motor because as you'd expect, its wet wet wet on
this boat, and ive already wrecked a couple of outboards. im hoping the
trolling motor will survive the water. the other advantage is its readily
available when needed, ive had a lot of trouble starting outboards in rough
conditions. being quiet is a nice plus.

im not too worried about all the controls, and was thinking of removing the
control panel from the outboard and chopping it down to a simple motor on a
bracket that i can easily flip into the water, and a simple directly wired
forwards/backwards switch with a fuse.

Any thoughts/advice on this? what sort of switchwear/wiring do i need to go
with, considering that its pretty much going to need to be submersible.
anything i can do to make the motor more robust? would sikaflexing any
joints help?

Shaun

Shaun Van Poecke wrote:
cross posted to rec.boats.electronics

hi all,
im hoping to install a trolling motor on a 14 foot beach cat, for those
interested, a local australian design the 'caper cat'. There is plenty of
reserve bouyancy and ctorage space in the hulls. The rough plan is to go
with two 75Ah AGM gel cel batteries, one in each hull. The batteries are
totally sealed and can be mounted upright, sideways or upside down, so im
not too worried about flying a hull. Ill need to mout the batteries somehow
in the hulls so they dont come lose and damage the boat.

im going with a trolling motor because as you'd expect, its wet wet wet on
this boat, and ive already wrecked a couple of outboards. im hoping the
trolling motor will survive the water. the other advantage is its readily
available when needed, ive had a lot of trouble starting outboards in rough
conditions. being quiet is a nice plus.

im not too worried about all the controls, and was thinking of removing the
control panel from the outboard and chopping it down to a simple motor on a
bracket that i can easily flip into the water, and a simple directly wired
forwards/backwards switch with a fuse.

Any thoughts/advice on this? what sort of switchwear/wiring do i need to go
with, considering that its pretty much going to need to be submersible.
anything i can do to make the motor more robust? would sikaflexing any
joints help?

Shaun


I routinely use Minnkota Endura outboards in salt water. I first paint
the lower unit with resin to protect it. The Enduras have only a rotary
switch in the upper unit. I find that for most applications I use only
the highest power setting. This connects the batteries directly to the
motor bypassing the "speed coils" used to resistively limit the motor's
power. If you remove the switch and wish to use only high power, the
speed coil leads can be stuffed into the tube leading to the lower unit
and any form of sealant used to close off the tube. At this point, the
motor could be run totally submerged. If you want speed control, you can
extend the speed coil leads as well as the battery leads, or add your
own pulse width modulating (or other type) external to the motor.

To mount batteries, I generally fiberglass in a footing of some kind and
provide hold down straps anchored to the footings. Two 75 amp hour
batteries would give you about 3.5 hours cruising with a 30 amp motor.
At 3.5 mph that would be about 12 1/4 miles. Note that I computed that
at the 70% discharge point for your batteries. Not going below that
point will extend the usable battery life.

Good luck on your project, and keep us posted.

BS

"R Swarts" wrote in message
...

I routinely use Minnkota Endura outboards in salt water. I first paint the
lower unit with resin to protect it. The Enduras have only a rotary switch
in the upper unit. I find that for most applications I use only the
highest power setting. This connects the batteries directly to the motor
bypassing the "speed coils" used to resistively limit the motor's power.
If you remove the switch and wish to use only high power, the speed coil
leads can be stuffed into the tube leading to the lower unit and any form
of sealant used to close off the tube. At this point, the motor could be
run totally submerged. If you want speed control, you can extend the speed
coil leads as well as the battery leads, or add your own pulse width
modulating (or other type) external to the motor.

To mount batteries, I generally fiberglass in a footing of some kind and
provide hold down straps anchored to the footings. Two 75 amp hour
batteries would give you about 3.5 hours cruising with a 30 amp motor. At
3.5 mph that would be about 12 1/4 miles. Note that I computed that at the
70% discharge point for your batteries. Not going below that point will
extend the usable battery life.

Good luck on your project, and keep us posted.

BS

nice idea about fibreglassing a foot into the hull... i was thinking about
how i was going to securely bolt a battery box in ;-)

when you say coat the lower unit in epoxy, do you mean the motor itself? do
you cover the entire motor (other than the prop/bearing)? did you coat the
upright shaft as well? running submerged would be a fair description of how
my cat moves through bigger swells.... i know this is going to cost me
about as much as a brand new outboard and have virtually zero re-sale value,
but if i can get a few years out of it Id be happy.

in all honestly, 2x75Ah batteries is huge overkill for me. I cant see
myself using it for more than an hour at a time, but i want plenty of
reserve in case i go out two days in a row, or decide to 'motor' a little
further.

Thanks,
Shaun