| Have tried different pitches on my inboard electric with good success. ie 12" diameter 2 blade 10" pitch drew 75 amps wot and got about 5.mph 12" diameter 3 blade 8" pitch drew 80 amps wot and got about 4.6 mph 12" diameter 3 blade 13" pitch drew 115 amps wot and gets about 6.2 mph or hull speed ***** The 115 amps at 36 volts wot is within the spec for the motor. After several miles at wot the motor is very warm but can be held by your hand without burning and water on motor does NOT boil. Temp control is ok for a maginally ventilated motor space. *** A non-standard prop voids most trolling motor warranties bc of possible motor overloading. The motors (almost all with 4" pitch) regardless of power rating are sold to power at fishing speeds for different weights of boats. The 36 volt motors can push a 20ft boat without overloading the motor at wot. If your motor is listed by the manufacturer at 60amps wot on a 3000-4000 pound boat and you have a 1200 pound boat, then wot will maybe only draw 35 amps at wot. IF this is the case then a steeper prop will give more speed but draw more amps at wot. IF the amps don't exceed the 60 in the spec at wot, then you are ok as the motor won't overload except possibly when fighting high winds and or current **** also you are subject to the rules of hull speed calculations as this affects ultimate top speed in a NON-PLANING HULL. ie Hull speed is approximately 1.3 times the square root of the waterline length of the hull. 9 foot waterline would be 1.3 x 3 = 3.9 kts 16 foot waterline would be 1.3 x 4=5.2 kts 20 foot is 1.3 x 4.47=5.8 kts My 23 foot Helson motorsailor has about a 20-21 foot waterline so I need to be happy with 6.2 mph at wot 4 mph draws 25 amps 5 mph draws 50 amps 6.2 mph draws 115 amps ****** To get 7 mph by over propping I might draw 250 amps and burn the motor, NOT worth the risk. ***** Using a 3 blade Motorguide trolling motor prop on a Minn Kota gave me the same amp draw but 0.3 mph more forward speed and DOUBLE the thrust in reverse. Reverse gear is the brakes on a boat. Well worth the effort, but the Minn Kota 2 blade (weedless) was better in forward in heavy weeds than the Motorguide. Hope this was helpful. Each boat is an experiment waiting to happen. Good luck Dave ( Day Dream Believer) --- On Sat, 10/2/10, alex <alex04032@yahoo.com> wrote:
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