relative or not? my 12' "mini-henley slipper launch" on a 12v 36lb thrust MK trolling motor, does 4.5 mph top speed well enough, is a 41" beam at waterline (600lbs). its spinning a 3 blade kipawa prop helps quite a bit. have had success with a 24v 250w scooter motor and a 5.5" youngs prop, was feeding it 12v instead of 24, wasnt fast but it sure had torque. youngprops makes some 7" props for 3/8 shaft, could be bored to 1/2 easy enuf. monsterscooterparts site has some 900-1000w motors and PWM speed controllers, if you have trouble finding a golf cart to cannibalize, might be good-cheep source. direct drive gives about 2500 rpm tops, no load. options are pretty easy for toothed belt or small chain reduction for lower rpms and bigger or steeper pitch props if wanted. 14ft sq-rt > 3.74 x 1.56 = 5.83 mph theoretical hull speed, x 0.75 = about 4.4 and 5.83 x 0.85 about 4.95 mph.. beyond that its likely to gobble the juice really hard! I also use a simple online calculator, is saying 1100lbs with 1.1hp doing a max of 7mph, is same to about 1320lbs drops to 6 mph.. 3/4 that being 4.5mph, is about what I'd expect from a 900-1000w motor. this all trolling motor speed stuff, is really all I know here. I have a 50lb thrust 12v motorguide and a 55lb thrust 12v MK sittin here, but maybe too small on power for a beamy little tug? they're about 570 and 600w. my little 12' toy does just as well, same speed and runs longer on the 400w 36lb MK. (its light is why) the 55lb MK has the shaft faired for less drag and a kipawa prop on it, with a spare stock one, its all new, newly "butchered to fit" and just sittin for now. if you want to go that route give a holler, its a mechanical speed controller and can show ya how to hook up a couple BIG microswitches to handle full speed without the controller gettin hot and stealing power away from the motor (simple as making the controller backplate into a cam-lobe for direct parallel feed), yeah its low tech low budget stuff. calc's here showing 0.8hp (600w) oughtta do 4 to 4.5 mph with 950 lbs, same kinda ballpark figgerin as above to arrive at that, and experience with the 12' toy. power demand usually goes up TONS above 75-80% of hull speed. for less speed but more grunt theres always the MK "weedless wedge" prop, it'll slow ya to 3mph but it'll move some weight! there is an advantage to the setup.. cut shaft trolling motor with a spool on top, rope and pulley steering, and a 5x13 (roughly) motor well.. is easy access. its using the stock MK clamp mount so if theres a prob its just 2 electric connecters, a couple carabiners to the steering and its in or out in a minute. I've run into water too shallow and tilt-raised it some to get loose a couple times. pod motor submersed is bit quieter than inboard too. theres 16v AGM's been looking at for a little more kick maybe. couple 1100 deep cycles to 600w oughtta run 4 hrs full tilt or 6-7 hr on MK's "4" setting. too rough or too windy is gonna affect a little tuggy quite a bit too for its wheelhouse. 6hp is about 4500w, depending on weight might be pretty overkill for displacement speeds, a pair of healthy scooter motors belted or chained to a driveshaft might be plenty for it, might be another option to play with. I'd think a couple 4-5-600w motors oughtta do well, full displacement speed only being the 5.8mph for its 14' length. if its got the right shape for it, that 6hp could put it up slow planing could be kinda cool too because it'd shed the displacement drag to get ya 1/2 as far and 3x as fast. not realistic for a tug but 13-14 mph is rollin pretty good if its a near flatbottom. --- On Sun, 7/22/12, AJ Gilchrist <andrew@fastelectrics.com> wrote:
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