Hi Larry,<br> I looked up yor motor in my
Advanced DC motor catalog and found that it is about 75%
effecient. That will account for some of the minor
differences in my model and your actual performance. I Also
noticed that the motor is rated at a maximum speed of
2100 RPM's that means that your motor will produce 4.2
HP at 2100 motor RPM's.(I am going to varify this
with KTA since they are about 8 miles away from me
this is very easy)<br> How is the motor connected to
the shaft. I assume that you have some kind of a belt
drive. What is the ratio?<br> a common misteak people
make when applying DC motors is to not gear them in
properly.<br> Remember that HP = Torque x RPM devided by either
63025 or 5252 depending weather you are talking about
inch pounds or foot pounds.<br> You should alway gear
the motor so that it will reach its Maximum RPM when
the load (your shaft) is at its maximum RPM's in you
case if you are looking for a maximum speed of 8 knots
then with you existing prop you will want to plan on a
shaft speed of 1475 RPM's That means that a 1.4:1 Ratio
would be ideal. anything less means that you are
wasting power. That means that you can actualy lower your
amps draw by selecting the right ratio. A 16 x 16 prop
would cause your shaft speed to be lowered for a given
speed and it would increase your thrust. But if the
thrust is needed the it would make sense. you motor amps
would go up however. If your motor is not geared at
1.4:1 then you should either change the ratio or select
a smaller prop.<br><br>Good sailing er a
motoring<br><br>Don
