Trolling motors, high performance props.

[Will Gilmore]

I have been researching the possibility of going electric for auxiliary motor on my '73 O'Day mariner 19. There are several sailors who use trolling motors on their mariners but whenever the subject comes up on their class web site, the debate ends with whoever asked the question just finding a 2 - 4 hp motor. I never get to hear any real agreements (pros/cons) that strongly lead to that decision.
I am looking at the Newport Vessels 86lb thrust motor ( https://newportvessels.com/electric-trolling-motor-86lb-thrust-saltwater-l-series/ ).
It is my understanding that trolling motors are limited in speed due to their props being specifically designed for trolling at 4 mph. I found this site ( https://www.kipawapropellers.com ) Kipawa makes aftermarket high performance props for trolling motors.
That and an undecided 24v battery and solar system are what I'm considering at the moment. The mariner displaces about 1350 lbs and draws 11" with cb up.
Does anyone have experience or opinions on any component or system for electric auxiliary power?
- Will ("off-grid", Dragonfly)

 

[Benny17441]

Trolling motor power is measured in lbs. of thrust and not horsepower. There is no direct mathematical conversion of thrust to horsepower. The best anticipated performance comparison equates a 70 lbs. of thrust trolling motor to a 1 HP gasoline outboard. I was not impressed by the Kipawa claim of a 10-15% improved performance. Understand the prop design does not stand alone; the design criteria for the motor is to troll an average fishing boat at slow speed and they will use the smallest motor that coupled with an adequate prop delivers the desired low speed at the motor's rated RPM. The motor will likely prove to be too small to drive a higher pitch prop. Yes, an improvement in materials and prop shape can perhaps account for a 10- 15% improved performance but in real numbers the increase of higher speed and travel distance may be insignificant for practical purposes. The use of an electric trolling motor can be adequate for a lake in calm conditions but would not be safe performance in high winds or sea swells. Now there are a couple of electric outboards using Lithium batteries that can give a very adequate performance but their cost is quite high. I still prefer a gasoline powered outboard that can be refueled in minutes rather than recharged in hours and can push through current and wind in an emergency. There are alternate electrical solutions but their cost is still much higher for similar performance. Some years back the Russians developed a very small nuclear reactor to power electric motors in pleasure craft. It would come with a maintenance agreement. I don't know if they sold any but even if I had the money I would not trust their manufacturing and quality control capabilities.

 

[Will Gilmore]

Benny,
Sounds like you have given some thought to this question as well. There are a lot of mariner owners who think 2hp is perfectly adequate. Certainly, hull speed is easy to achieve on such a small boat. Just as you noted, wind and waves play a factor beyond that. I am not looking to turn my little weekender into a motor sailer, nor am I looking to just get her from trailer to rigging dock.
What I like about electric is:
1. the possibility of refueling without a gas pump. (Solar, wind, drag-behind inducer)
2. Very quiet and no smell.
3. Small and light.
4. Swamping in a following sea shouldn't be an issue if properly water proofed.
I've sailed boats that had no motors at all and been in situations I couldn't sail out of. Had to used the anchor to avoid crashing into a bridge in 30 knots of wind. Certainly it's nice to have the power to motor when you want it. However, there will be times when nothing is enough.
What I see my needs being are to dock in light to medium winds, getting through a pass or under bridges, possibly saving myself when wind is not present.
I can't afford a Toquedo and I haven't they are that much more powerful than a larger trolling motor anyhow.
I'm going to put an electrical system on board so battery weight won't add to my displacement.
I've heard the arguments that when you are out of battery power you're out but doesn't that hold true for gas too? Even more so, since you can't get more gas without a gas station.
- Will (Dragonfly)