Just a quick question... what is the proper depth of a transom mounted
electric trolling motor for the best efficiency in the water? Do I want to
prop to be even with the bottom of the boat (a 12' jon boat), or down to its
deepest length? I have a 36" Minn kota transom mounted electric and a
fairly shallow stern/transom, so the motor/prop probably would be able to be
18" to 24" or so below the waterline at its deepest setting.

--
Marty S.
Baltimore, MD USA

You will want it deep enough to turn 360 degrees without hitting the boat.
If it is too shallow, it will produce a ripping/sucking sound; too deep, and
you will be picking up weeds and risk damage from striking submerged
objects.
----------------------
I once mounted a 20# electric under the front seat of a 17 foot canoe. That
little motor would produce 7 knots; fast enough to troll for salmon. It
was done with a foot long aluminum tube with a flange welded on one end for
bolting to the bottom of the canoe. The tube came up beneath the front
canoe seat. (and was braced at the top.) This produced a watertight shaft to
hold the motor shaft. The motor shaft was cut and fitted with a bicycle
sprocket at the top. (electric wires passed through the center of the
sprocket) The sprocket was for steering. A short bicycle chain was wrapped
around the sprocket for positive steering. A 1/2 inch pvc pipe was flexed
around beneath the curved gunwale on one side to guide the steering rope to
the rear seat. (the other end of the chain was tensioned with a long spring
found at the truckstop for retaining brake hoses against the cab) Wiring
for the motor was fabricated to the rear seat. Floatation foam was added to
offset the weight of the battery and the entire canoe was covered with 1/4
inch plywood, pop-riveted to the aluminum gunwale. (except for my rear
cockpit, of course).


When I pulled into the dock, the attendant always tried to sell me
gas......haha. None of the motor showed above the boat. Having the motor
in front produced unbelievable maneuverability. When the salmon were
running, I would cruise by with my canoe paddle, making a paddling motion,
but not touching the water. Being silent and doing 7 knots really freaked
out some folks, especially when I backed into shore and pulled her half out
onto the beach.

Pepperoni

"Marty S." wrote in message
...
Just a quick question... what is the proper depth of a transom mounted
electric trolling motor for the best efficiency in the water? Do I want
to
prop to be even with the bottom of the boat (a 12' jon boat), or down to
its
deepest length? I have a 36" Minn kota transom mounted electric and a
fairly shallow stern/transom, so the motor/prop probably would be able to
be
18" to 24" or so below the waterline at its deepest setting.

--
Marty S.
Baltimore, MD USA

Deep enough so that none of the 'cone' of thrust is being deflected by the
transom when moving in reverse.

RichZ©
www.richz.com/fishing

Other than picking up weeds and possibly hitting bottom, then the motor is
as efficiently moving the boat at it lowest mounting point as if it is
raised to be even with the bottom of the stern?

--
Marty S.
Baltimore, MD USA


"Marty S." wrote in message
...
Just a quick question... what is the proper depth of a transom mounted
electric trolling motor for the best efficiency in the water? Do I want
to
prop to be even with the bottom of the boat (a 12' jon boat), or down to
its
deepest length? I have a 36" Minn kota transom mounted electric and a
fairly shallow stern/transom, so the motor/prop probably would be able to
be
18" to 24" or so below the waterline at its deepest setting.

--
Marty S.
Baltimore, MD USA

Marty S. wrote:
Other than picking up weeds and possibly hitting bottom, then the motor is
as efficiently moving the boat at it lowest mounting point as if it is
raised to be even with the bottom of the stern?


Usually the blades should clear the bottom of the boat by about two to
three inches. If you drop it real deep you will discover a speed loss
plus it puts more strain on the motor itself, least this has been my
experience with electric trolling motors.

Jerry

"Marty S." wrote in message
...
Just a quick question... what is the proper depth of a transom mounted
electric trolling motor for the best efficiency in the water?

Mounting it deeper will result in more shaft dragging in the water and more
flex in the shaft (which will cause the motor angle to change, reducing
efficiency).

The shallower the motor is the more cavitation will result. Minor cavitation
will have a small impact on efficiency, and will greatly increase the
propeller noise (only an issue if you are trying to be quiet for fishing
purposes). If it is too shallow, it could even suck air from the surface,
which would have a dramatic impact on performance.

For low speeds, the interference from the hull of the boat will be minimal.
As the speed increases, the flow of water from the hull could create eddy
currents around the transom, which if the motor was too shallow could cause
additional cavitation.

Basically, I would recommend mounting it so that the top of the prop is a
couple of inches below the bottom of the boat. Any deeper and it creates
unnecessary draft concerns, any shallower and the prop may hit the bottom of
the boat if you spin the motor too far around.

Rod

On Fri, 25 Jun 2004 10:13:22 -0400, "Marty S."
wrote:

Other than picking up weeds and possibly hitting bottom, then the motor is
as efficiently moving the boat at it lowest mounting point as if it is
raised to be even with the bottom of the stern?

At it's lowest point, force applied to the shaft will "try" to raise
the bow of the boat ( I seem to remember "vectors" from my school
days) and raising the bow with a trolling motor is wasted energy.

I would imagine that the best place to apply a forward force to a boat
would be right at the water line. Imagine pushing a boat in shallow
water. Obviously, with a propeller, this is impractacle.With the top
radius just a few inches below the hull seems the best compromise.

If you have a regular outboard too, you may want to set your trolling
motor skeg slightly lower than your gas engine. This will help prevent
you digging your main prop into the mud in shallow waters and having
to jump out and free it!

Interesting. Can you post a picture of this setup. Thanks,

"Pepperoni" wrote in message
...
You will want it deep enough to turn 360 degrees without hitting the boat.
If it is too shallow, it will produce a ripping/sucking sound; too deep,
and
you will be picking up weeds and risk damage from striking submerged
objects.
----------------------
I once mounted a 20# electric under the front seat of a 17 foot canoe.
That
little motor would produce 7 knots; fast enough to troll for salmon. It
was done with a foot long aluminum tube with a flange welded on one end
for
bolting to the bottom of the canoe. The tube came up beneath the front
canoe seat. (and was braced at the top.) This produced a watertight shaft
to
hold the motor shaft. The motor shaft was cut and fitted with a bicycle
sprocket at the top. (electric wires passed through the center of the
sprocket) The sprocket was for steering. A short bicycle chain was
wrapped
around the sprocket for positive steering. A 1/2 inch pvc pipe was flexed
around beneath the curved gunwale on one side to guide the steering rope
to
the rear seat. (the other end of the chain was tensioned with a long
spring
found at the truckstop for retaining brake hoses against the cab) Wiring
for the motor was fabricated to the rear seat. Floatation foam was added
to
offset the weight of the battery and the entire canoe was covered with 1/4
inch plywood, pop-riveted to the aluminum gunwale. (except for my rear
cockpit, of course).


When I pulled into the dock, the attendant always tried to sell me
gas......haha. None of the motor showed above the boat. Having the
motor
in front produced unbelievable maneuverability. When the salmon were
running, I would cruise by with my canoe paddle, making a paddling motion,
but not touching the water. Being silent and doing 7 knots really freaked
out some folks, especially when I backed into shore and pulled her half
out
onto the beach.

Pepperoni

"Marty S." wrote in message
...
Just a quick question... what is the proper depth of a transom
mounted
electric trolling motor for the best efficiency in the water? Do I want
to
prop to be even with the bottom of the boat (a 12' jon boat), or down to
its
deepest length? I have a 36" Minn kota transom mounted electric and a
fairly shallow stern/transom, so the motor/prop probably would be able
to
be
18" to 24" or so below the waterline at its deepest setting.

--
Marty S.
Baltimore, MD USA

No, The boat is gone. I do have a new tube made for the next model. It is
in storage, but I will try to locate it. It is actually quite simple. I
hauled the canoe on top of my truck. The steering was a simple lever; the
spring deflected the motor fully in one direction, so when the lever was
centered, it produced straight travel. The only problem was that the
aluminum tube eventually welded itself to the stainless motor shaft. The
new tube is large enough to place a pvc wrap between the new shaft and the
aluminum tube.
http://home.comcast.net/~thuxton/drawing.jpg

The stuffing tube is bolted to the canoe bottom and sealed with a rubbery
vinyl "bathtub calk" which sets firm quickly. The tube provides watertight
passage through the hull, and also a long bearing surface for the motor
shaft. The tube was braced near the top by a simple crossmember with a hole
through which the tube protruded. Attaching the sprocket to the top of the
tube requires a bit of fabrication or ingenuity. I used an end cap from a
truck shock absorber which happened to have the correct diameter to fit the
motor shaft.

Pepperoni

"Jey Jeyasingh" wrote in message
...
Interesting. Can you post a picture of this setup. Thanks,

"Pepperoni" wrote in message
...
You will want it deep enough to turn 360 degrees without hitting the
boat.
If it is too shallow, it will produce a ripping/sucking sound; too deep,
and
you will be picking up weeds and risk damage from striking submerged
objects.
----------------------
I once mounted a 20# electric under the front seat of a 17 foot canoe.
That
little motor would produce 7 knots; fast enough to troll for salmon.
It
was done with a foot long aluminum tube with a flange welded on one end
for
bolting to the bottom of the canoe. The tube came up beneath the front
canoe seat. (and was braced at the top.) This produced a watertight
shaft
to
hold the motor shaft. The motor shaft was cut and fitted with a bicycle
sprocket at the top. (electric wires passed through the center of the
sprocket) The sprocket was for steering. A short bicycle chain was
wrapped
around the sprocket for positive steering. A 1/2 inch pvc pipe was
flexed
around beneath the curved gunwale on one side to guide the steering rope
to
the rear seat. (the other end of the chain was tensioned with a long
spring
found at the truckstop for retaining brake hoses against the cab)
Wiring
for the motor was fabricated to the rear seat. Floatation foam was
added
to
offset the weight of the battery and the entire canoe was covered with
1/4
inch plywood, pop-riveted to the aluminum gunwale. (except for my rear
cockpit, of course).


When I pulled into the dock, the attendant always tried to sell me
gas......haha. None of the motor showed above the boat. Having the
motor
in front produced unbelievable maneuverability. When the salmon were
running, I would cruise by with my canoe paddle, making a paddling
motion,
but not touching the water. Being silent and doing 7 knots really
freaked
out some folks, especially when I backed into shore and pulled her half
out
onto the beach.

Pepperoni

"Marty S." wrote in message
...
Just a quick question... what is the proper depth of a transom
mounted
electric trolling motor for the best efficiency in the water? Do I
want
to
prop to be even with the bottom of the boat (a 12' jon boat), or down
to
its
deepest length? I have a 36" Minn kota transom mounted electric and a
fairly shallow stern/transom, so the motor/prop probably would be able
to
be
18" to 24" or so below the waterline at its deepest setting.

--
Marty S.
Baltimore, MD USA