Re: trolling motor to horse power ??????
Here's the correct formula used in marine applications.....more commonly known as Bollard thrust or Bollard pull.<br /><br />thrust = 62.72 X {[HP at propeller X (propeller diameter/12)] exp .67}<br /><br />If you know the thrust you can find the prop shaft HP. If you know the prop shaft HP you can find the thrust. But there is no direct correlation.<br /><br />I wouldn't recommend using JB's method. First it will not give you the motor's HP at the prop shaft. Granted, losses through an electric motor are minimal compared to a gasoline outboard, but none the less thrust (and hp) in these applications are measured at the prop, not the engine. Secondly, thrust is a static measurement in pounds. It can hardly be related to Watts, HP, Work, etc because of distance and time properties.<br /><br />An example and comparison would be Yamaha's 9.9 HP 2-stroke and their 9.9 HP 4-stroke high thrust model. Both have the same HP, but the high thrust model produces much more thrust. Or you could compare both the 9.9 4-stroke and the 9.9 4-stroke high thrust. Both exactly the same engine. But the gearing and propeller changes result in major thrust differences.<br /><br />Really all you need to know from the manufacturer to do it right smokinjoe is the ideal propeller diameter of your motor in question. From there it's plug-and-chug. Hope this helps.
