On Mon, 30 May 2005 04:07:00 -0400, tedwilliams wrote:

On Sun, 29 May 2005 21:32:39 GMT, skddjl (Mic) wrote:

///
"NOTE: There is no neat formula or correlation between thrust and
horsepower.///

There is in fact a formula which relates thrust to horse-power and
water speed.
Simply put: thrust in lb. =
( power in watts / speed through water in MPH )
X 0.1 scaling constant

Example: 1/2 HP = 373 watts,

water speed 1 MPH

thrust = 373watts /1 mph X 0.1 = 37 lbs

water speed 2 MPH:

thrust = 373watts / 2 mph X 0.1 = 18 lb thrust

Notice that the big unknown is the water speed. Even if a boat is
anchored, the propeller will push water at 1 mph or 2 mph depending on
its size, pitch etc. You can take 1 mph as a lower limit - usually
higher. This is higher than the other unmentioned
losses - motor efficiency 90%? prop efficiency 80%??

Brian Whatcott Altus OK