Trolling motor pitch

Planning On installing a trolling motor on my pro angler. I been searching the old thread bout installing trolling motor on kayak but no one seems to know who sells the right prop (pitch) or it don't exist. It's 2016 and I figure there should be a company out there that's made one. Any of you fellow know of any or know any aftermarket prop that will get my trolling motor moving more then 5 mph. I have a 30 lb min Kotta.

Thanks and have a nice day

From what I recall about reading past posts of PA-14's with a electric trolling motor, is 5 mph is close to the top end you can expect. A higher thrust motor won't help either.
It just consumes more DC current.

_________________
Dr.SteelheadCatcher
Warrenton, OR

No such prop currently exists, and as you guessed, it's the missing link to get more speed out of kayak. A few years back I tried the prop from a Native Propel unit, figuring that it's greater pitch would be able to take greater advantage of a trolling motor's RPM. But the pitch was too great and the motor wouldn't turn it more than about 20RPM. Not much good on the motor, either. So we started trimming it shorter and finally arrived at a good working compromise. We could push about any kayak around 6.5 MPH with it. It was difficult to mount and without precise balancing we never did get all the vibration out of it. But it did get the extra speed.

We had thought about looking at RC Airplane props as another alternative but as we moved on to another project that fell by the wayside.

Hmm... I did read some form about using rc prop. Maybe Ill jump on that and take a chance . The mean time thanks for letting me know guys.. Have a great day

Rc airplane props do work, and they are cheap with many available pitches and diameters available. You will have to make a special hub to hold them, but that's a one time deal (the hubs on RC props are pretty standardized), you will go thru quite a few (i'm guessing a half dozen or so) to get the right pitch and diameter dialed in (it's a trial and error thing). Once you get the right pitch you just keep reducing the diameter until you can fit your motors HP profile so you can get to full rpm.
Just to get a feel before doing anything else, just go to a hobby shop and pick up say a 12 inch dia x 6 pitch nylon RC prop. Hook it to a cordless drill on an extended rod, drop it in your pool and turn the drill on, you will be amazed at how much water it moves (i had difficulty holding onto my drill).
Adjusting the diameter is pretty easy if you clamp an axle pin to your disk sander table and sand down the diameter on the prop to suite your motors max horsepower, balance should remain pretty good as long as you remain accurate around the axle.
How long those props will work I have no clue.
I'm just guessing here but I would guess all standard trolling moter props have about a 2-3 inch pitch, enough to push a 16 ft powerboat (3000 lbs) at 3-4 mph (seems to be the industry standard anyway), none of the manufactures could care less about us kayak people (just sayin).
Hope this helps
FE

Thanks a lot guys... Very good info on the rc prop. I'll prob do what fusioneng suggested, experiment with the rv prop and to find out. Hope the rc prop works if not I'll probaly just replace the prop with the Kipawa 314. One person says it does help a lil and give more thrust.

Thanks guys

The Kipawa's three blades get you up to speed faster than the standard two blade. It does not give you more speed sorry to say.

Will try Native Propel prop with my 24# Watersnake. As-is, I can hear heavy cavitation when in full power. Was the final D you brought it down to ?

If I can get another mph while keeping the current draw the same, would be a win in my book, worth trying methinks

Not sure if it will be any help but I did a lot of experimentation with prop pitch with my Honda 2.3 outboards, the data may corelate.
I mounted 10 inch pitch props on my 2.3 honda's, the props were 10" dia and designed for a 10 hp outboard. I reduced the od to 7 inches and still couldn't get engines to full rpm. I'm pretty sure 6.5 inches dia would have been ok, with twin motors I could have got the engines to near full rpm. I never reduced the dia down from 7" because the props served my purpose (the engines only provide a portion of my hp propulsion needs (the wing and sails supplies the rest). In other words reducing the dia 65% reduces the hp requirement by 3/4ths. In rough numbers reducing a ten in prop designed for a ten hp motor can be driven by a 5hp motor if you reduce the dia to 7.5 inches (if my math is right).
With the 10" pitch props my max speed (when motors reach full rpm) is 20 mph, any faster and the motors blow up (unless I pull the motors up of course). With my 7 inch props 15 mph is max.
FE

Guess the Kipawa idea is out the door for me anyways thanks for all the good info guys.
Keep it comming if u have anymore so this thread can be useful for Hobie owners later on and if anybody ever figure out how to tweek the prop, please do share.

Thanks and have a great day

The whole key here is to always keep in mind the propulsion horsepower required goes up exponentially with speed.
Here is a link to a handy calculator that can help you decipher the information ( http://www.psychosnail.com/boatspeedcalculator.aspx).

Using an example of a 13 ft boat weighing 200 lbs, the calculator spits out the horsepower required to go 6mph is .6hp (which is more than your 30lb motor can deliver). Then if you change the desired speed to 7mph, then the HP requirement goes up to 1.63 hp required to propel the boat 1 mph faster. Then to propel the boat to 8 mph requires 7.29 hp. Believe it or not these numbers are fairly accurate.
Obviously some numbers change if you have a planing hull, and can get the boat up on plane.
This is all why the actual propeller pitch is all important, as an example if you have a 30 lb thrust motor, it will propel your boat up to say 5mph, then you switch that motor out for a 55 lb thrust motor, with the same pitch propeller you will find the boat goes no faster, this is because you are limited by the propeller pitch. Obviously with a 55 lb pitch prop you can propel a much bigger boat up to the same speeds, but your smaller boat won't go any faster (if you are not horsepower limited), you typically just end up running your battery down faster as Tom K pointed out, but your not going to go any faster.

Now comes the twist to the story and stuff to think about. The horsepower requirements are hard fast physics and if your only source of propulsion is the trolling motor, you are limited by the physics. However the trolling motor alone doesn't have to be you sole means of propulsion. In my case with my tandem island my twin Honda 2.3 outboards only provide a small portion of my total horsepower requirements (about 40% to 50%). All calculators out there assume the motor to be your sole source of propulsion, and typically revolve around a 16 ft 3000 lb boat (the industry standard), this is why the results are typically wrong.
Your max speed is regulated by your motors horsepower, rpm, and your propellers pitch, if you exceed the max speed/rpm/pitch of the motor, then the motor/prop is just being dragged thru the water, with great risk of exploding the engine (I have exploded two engines this way via over revving).
Now using the above calculator enter in an 18.5" length (length of my TI), the max hull speed comes out to about 11.6 kts. Now on the next page enter in 400 lbs for the boat weight, because the boat is so light (they are expecting a 3000 lb boat ( lol)), this skews the numbers a little, the max speed now reads 12.6 knots (a little higher, kind of assuming the boat will rise out of the water some).
Now you can calculate how much horsepower your mirage drives deliver, and your sails horsepower output generated separately, then add to the total HP delivered (of course there is some loss here). So lets say when you peddle only in flat water and no wind your peddling effort gets you to 5mph (a reasonable number for non-athletes). The actual horsepower generated by your leg power is .34 horsepower. Now calculate the horsepower generated by your sail alone (if you have one). Lets say on a reach in a 10 mph wind the boat goes 6mph (a reasonable number, ( the TI typical speed is .6 of windspeed). The calculator tells us the sail is generating .58 horsepower. Now the delivered horsepower of the trolling motor alone (working on flat water with no wind lets say is 6 mph, that motor is delivering .58 hp of propulsion. Now if you add the 3 together this is your horsepower output (.34 + .58 +.58 = 1.5hp).
Now lets say you are peddling and sailing (both at the same time), and the boat now travels at 7 mph. Figuring 7 mph as the starting point for your prop pitch calculations ( basically figuring the boat is already going 7 mph when you drop the motor in the water and try to add propulsion (the props need to be pitched with this factored into the equation).
It works out that a Honda 2.3 with a 4.5" pitch prop propels the boat to around 6 mph so we will be using that number as the floor for our pitch calculations.
In my case the boat is already traveling 7 mph (via sailing and pedaling) when I drop the motor in the water and rev it up, with a 4.5 inch pitch prop the boat actually slows down because I am dragging the propeller thru the water (we have already determined at max rpm the boat travels 6 mph at max rpm via motor propulsion alone (obviously there is some loss there, but not much)).
Obviously there are a million overlapping calculations involved here, but in the above calculations with the boat already traveling at 7 mph via sail and pedal power, dropping the motor in the water with a 7 inch pitch prop, the horsepower of the motor output added to the total horsepower, propels my TI to around 8 mph, above that speed the motor is horsepower limited (can't get to max rpm). All these numbers are based on physical trials while sailing/peddling/motoring with a single 2.3hp Honda in the water providing it's share of the propulsion requirements.
Now you still have to keep in mind that the horsepower requirements go up exponentially with speed, so doubling your horsepower does not even come close to doubling your speed, especially as you get closer to hull speed.
In my case I added a second Honda 2.3 engine with a 7 inch pitch prop, now my cruise speed in the same wind speed and conditions is 10 mph (previously 8 mph), at this point apparent wind (across the wing sail) begins to muddy the equations (this is why my fastest point of sail is upwind (because the faster the wind is going over the wingsail, the more horsepower the wing sail generates, basically you are adding the natural wind plus your forward motion wind together to get the apparent wind across the surface of the wing...).
Now with both of my motors running at max throttle with no sails and not peddling, the twin engines propel the boat to 10-12 mph (at WOT). The 7 inch prop pitch theoretically at max engine rpm is 15 mph, however the engines cannot deliver enough horsepower to propel the boat to 15 mph ( I'm horsepower limited with just the engine horsepower with those propellers). If I want to go any faster I have to get my additional horsepower requirements by other means (ie...sails and peddling).
It all boils down to how fast you want your regular cruise speed to be, then equip the boat and propeller pitch accordingly. In my case my preferred cruise speed is 8-10 mph in light winds, (any speed lower than that in the hot florida sun in the summer is unbearable, with great risk of heat exposure). Also a big factor is how much fuel you want to use, and how loud the engine noise you can tolerate is. In my case I only ever run my engines at less than 1/4 throttle, with the underwater exhaust they are very quiet and you can easily talk over the engine noise (at 1/4 throttle the engines output aprox 3/4 hp each), at that throttle setting I get aprox 2-3 hrs of run time per tank of fuel if I pedal and sail at the same time (each fuel tank is 1 quart).

In other words, by being creative, if you use your Torqeedo plus pedals, plus a Hobie sail kit you can greatly increase your speed and range.
Hope this helps
FE

A 403 set up right will easily get you over 6 fully loaded but it will cost you...