HP rated at prop / HP rated at crank

[Joe Raimondo]

How much H.P. is lost from the crank to the prop ? What is the average % diff between the two ? If you dyno a stock 115 V-4 Yamaha at 5500 RPM at the prop how much more HP would a dyno show if it was tested at the crank ? Joe Raimondo

[seahorse5]

For over a quarter of a century now outboards are rated at the propshaft, not the crankshaft.

gear losses varied about 5-8% loss, depending on design and power output.

[robert graham]

It's a pretty good guess that the motors are tested, modified and tuned at the factory, under load with the test propellers, so all readings would be at the propeller shaft.