The specs for that trolling motor say minimum draw 9 amps, max draw 20 amps. So with your little 11 amp-hour battery, you'll get maybe an hour at minimum draw, and half an hour or less at max draw. Some basic electrical math: 11 AH divided by 9 A = 1.2 H. Please don't head out on a 5 hour tour (or even a "3 hour tour" :-) without other means to get back if the wind dies...at medium draw (15A) you'll get about 40 minutes of runtime at best. You can get a 50AH or 60AH or more lithium battery, and it will be much lighter than same capacity lead-acid, but it will also lighten your wallet by a whole lot more. cheers, John On 10/15/20 9:09 AM, casioqv@usermail.com wrote:
I've been playing with using a 12V trolling motor on my M15 along with a cheap "Golf Cart Voltage Converter" to use a 48v electric bike battery pack with the trolling motor. It seems to work very well so far, but doesn't have quite the thrust of a gas outboard... good enough for exiting the marina, but not for motoring into a chop. The weight and runtime is comparable to a Torqueedo but at a tiny fraction of the cost. I've never ran it empty, but I suspect I can motor for 5-6 hours on the battery at about 3 knots.
Here's what I have: -DPLANET 30A 360W 12v Golf Cart 48V 36V to 12V Converter ($35 on Amazon) -Watersnake T24 ASP Saltwater trolling motor - designed for Kayaks ($150 on Amazon) -2017 Rad City Battery Pack 48V, 11.6 Ah (557 Wh) (from my eBike, but $399 new)
Total weight of this setup is 14.1 lbs with 7.4lbs for the battery, and 6.7lbs for the motor (converter is small and negligible). This is comparable to the lightest gas outboard I think has ever been sold- the 1.5hp Cruise'N'Carry at 12lbs. I used to have a Cruise'N'Carry, and found it to be cheaply made and extremely loud, so not really viable.
A big 24v 80lb thrust trolling motor would probably push the M15 at near hull speed and into a chop, but would be much much heavier than a comparable gas outboard, and requires dual large heavy batteries.
Sincerely, Tyler '81 M15 #157 S/V Defiant
----- Original Message ----- From: "Rimantas Aukstuolis" <raukstuolis1@gmail.com> To: "For and about Montgomery Sailboats" <montgomery_boats@mailman.xmission.com> Sent: Thursday, October 15, 2020 8:18:41 AM Subject: Re: M_Boats: changing Honda 2/2.3 prop
What about those electric trolling motors? Hard to figure out thrust/power/torque comparisons. What little I know, comparing them to expensive Torquedo is that they use bulky 12 volt batteries vs lithium. Any thoughts? Rimas Aukstuolis
On Thu, Oct 15, 2020 at 11:14 AM Alex Conley <conley.alex@gmail.com> wrote:
Thanks for the caution re overpropping. I guess the real solution would be to change the gear ratio to turn a larger prop slower at a given throttle setting. Then you could use more of the engines range and gain both torque at higher speeds and a slower low speed- both on my wishlist. But not a mod I can see making- it’d be a whole new lower end... It seems most of the little outboards we use on our displacement sailboats are geared to get a little inflatable zipping around; have there been attempts to make an outboard geared for small sailboats, or is it just too niche a market? I’ll plan to live with my imperfect 35 yr old motor long enough to hopefully hit the point where the range/cost ratio of the electrics makes them a good replacement....
On Wed, Oct 14, 2020 at 8:10 AM Dave Scobie <scoobscobie@gmail.com> wrote:
Alex:
Somewhere a few years ago I read about a person changing out the prop on the small Honda - wasn't a Mboat. I can't remember any specifics.
The general consensus was the problem is the motor will likely be overstressed under the load - especially a concern with the powerhead being or cooled.
:: Dave Scobie :: M6'8" #650 :: SV SWALLOW - sv-swallow.com :: former owner M17 #375 SWEET PEA - m17-375.com :: former owner M15 #288 SCRED - www.freewebs.com/m15-named-scred/
On Wed, Oct 14, 2020, 8:03 AM Alex Conley <conley.alex@gmail.com> wrote:
Ive also searched for a high thrust prop for my 35 yr old Honda 2 hp but never seen one. In these days of 3D printers/milling, strong plastics and computer designs, it would seem there might be an opportunity for someone to work up some designs that could then be made on order.
-- John Schinnerer - M.A., Whole Systems Design -------------------------------------------- - Eco-Living - Whole Systems Design Services People - Place - Learning - Integration john@eco-living.net - 510.982.1334 http://eco-living.net http://sociocracyconsulting.com