I hope nobody thought I was recommending using 24 V on a 12 V motor. My
motor is designed for 24 V so it is not inclined to overheat and burn up at
that voltage. Others are designed for 36 or 48 V. I think the advantage of
the higher voltage is to get more power without a proportionate increase in
current, which would require heavier wiring.
I just checked the MinnKota specs. My 24 volt RT70/S (70 lbf thrust) uses
45 A at full power, not 50 A as I think I said.
The next size smaller in the RipTide series is the 12 volt RT55/S (55 lbf
thrust), which uses 55 A at full power.
According to MinnKota, the RT70/S is supposed to be adequate for a boat up
to 25 ft weighing 3500 lb. The RT55/S is rated for a boat up to 22 ft
weighing 2500 lb. That seems very optimistic to me. They are probably
assuming a bass boat trolling slowly in quiet water and no wind.
Today, in my heavy first-generation P14 with the RT70/S, I used 100% power
to motor, sails down, at 3 plus knots, head-on against a 15-20 knot wind.
The power was quite adequate to get me where I was going in a reasonable
time, but was less than most gas outboards, including Dave Kautz's Mercury
(2 hp?) or my own 3 hp Seagull.
The clean, quiet performance and the positive control of the electric motor
are wonderful. I only take the Seagull if I need its greater range. On a
windless day (or downwind) I use 50-75% power to extend the range of the
electric. I recharge the batteries as soon as the boat is back in my
driveway, and I top off the charge the day before I plan to use it again.
MotorGuide has some motors that use either 12 or 24 V.
Harry Gordon
P14 #234, Manatee
Mountain View, CA