by DanaDCole on Thu May 21, 2015 9:02 pm
Crag,
My understanding is that, since this is a keel boat, it cannot go faster than the hull speed which is a little over 5 knots (except in the case of the rare "surfing" event). That rule holds no matter how large a motor you put on the boat, so there is no point in any more than 2 or 2.5 HP, which will easily take it up to hull speed. It's like comparing apples and oranges, but I believe a 50 lb thrust motor generates the equivalent of about 2 to 2.5 hp.
I took a ride in Charles Huie's PocketShip with a 2 HP Lehr (running on propane). It had us clipping along nicely against a pretty strong headwind, mast up. If you don't go electric, I suggest you take a good look at the Lehr ($1,000). More expensive than the Suzuki, but well worth it. No pollution and no annoying fumes.
As to range, there are lots of variables, but in general, according to Torqeedo their Travel 1003 with built-in battery will run for about 3 1/2 hours at half-throttle (3kts) or 35 minutes at full throttle (5kts) (or at 2kts it could run for over 10 hours). BTW, I was mistaken, their replacement battery costs $700, not $600. (The $600 battery is for the 503.)
I couldn't find any range figures on the Minn Kota site, but they do say that the maximum amp draw on the 55 lb thrust motor is 50 amps, so at full speed with a 100 amp-hour battery it theoretically would run for two hours. Considerably longer I'm sure at lesser speeds (interpolating from Torqeedo's figures, it should run 12 hours at half-throttle). All this assumes no other draws on the battery, which would be rare, but if you're running some LED lights and a small radio you won't be adding much load. I should also point out that trolling motors automatically shut down when they overheat, so if you use one for extended runs you may be stopping now and then to let the motor cool (and allow the solar panel to start bringing the battery back up). (I once capsized my Skerry and was pulled in by a guy with one of those big bass boats using a small trolling motor. I was hanging on to the boat while still in the water and was astounded by the power of that little motor. There was a hell of a lot of drag and he pulled it all in at a pretty good clip--I had to hold on tight.)
I'll be happy when I get the boat built and do some testing so I can report successes and/or problems to readers re the Minn Kota (or some other brand) trolling motor.
All that being said, I am not planning to run any races under motor power, or to drive around for extended periods. All I'm needing is some help getting out of difficult or dangerous situations near docks and that sort of thing, so I will most certainly not be using the motor much.
Question for Shudoman: I have read that the Torqeedo is pretty flimsy. Have you found that to be true?