Ok I have recieved the inline scale I purchased and have tested for static lbs of thrust that my 4hp johnson outboard provides on my sailboat. The scale is rated from 1 lb to 3000 lbs in 1 lb increments with a digital readout and is certified. I tested three times to make sure it was consitent. I also created a bridle from the aft deck cleats to tie the scale to so that thrust was measured by pulling on a line that ran down the center of the boat from the bow to the center of the transom.
at an idle 15 lbs of thrust +- 1 lb
at half throttle 60 lbs of thrust +- 2 lbs
at full throttle it varied by about 10 lbs ranging from 120 lbs of thrust to 130 lbs of thrust. This was not a variation from one test to the next but a variation within each of the three tests while at full throttle.
I just got tired of everyone saying oh its this strong or that strong but never giving apples to apples comparisons or any imperical evidence for IC (internal combustion engines) to electric. So now you know that on a mid 90’s 4hp johnson that it has a average thrust at full output of 125 lbs of thrust. Since I believe that electric motors. especially trolling motors are rated this way we can now start to build some realworld comparisons. This engine will drive my 87 F235 Beneteau 23.5 ft long 8 ft wide and weighing about 3500 lbs at 5.5 knots to 6.2 knots if the boat is well balanced.
Here is a video of the last of the three tests. Readings in it were a bit higher than in previous tests. This was I think due to the pull being more inline with the centerline of the boat. Static thrust test on Sea Puppy
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