In the "Roaring Twenties" (Under water exhausts were rare – 8^D ) it was discovered horse power sold motors. Engineering departments fiddled with the prototypes to get the maximum possable. Unfortunately production motors were not as carefully assembled. This led to most outboards over 4 horse power falling far short of there advertised rating. Sniping by competitors and complaints from customers led to the outboard builders forming the National Outboard Association as a group to rate others motors horse power. Competitors representatives would come into the factory and randomly pick three motors off the assembly line. These were run in and adjusted. They were then put on a dynamometer and the horse power average (to the nearest tenth) of those three became the certified horse power for that model. In a single year (1933) some models lost 20% of there advertised horse power. This rating method continued through the war years of the mid ’40s. It was virtually destroyed by Carl Kiekhaefer who refused to join, and found great commercial success in under rating his Mercury outboards. So ratings became more a product of the advertising department until the Federal Government copied a European trend, and mandated uniform power measurements taken at the propeller shaft.

In the dawn of outboard use, manufacturing was, of course, rather primitive. Measurements could change by how tight a production worker screwed there micrometer. Precision we take for granted today was totally unknown back then. This was also true in the oil & gasoline industry. Motors had to be designed to work under the worse conditions encountered. The fuel you bought today might be different from that bought last week, even though coming from the same gas station. Ole Evinrude was a great engineer and tireless craftsman. In the beginning (First 50 outboards) he built and tested each motor. To make his products easy to use, he attached a metal tag to the fuel adjustment needle valve indicating the adjustment needed for optimal starting and reliable operation. This continued until production accuracy allowed for the adjustments to be incorporated into the engine.

. . . . . . 😀

The fuel adjustment tags were attached to the carburetors. The NOA Horsepower Certification medallion was usually on the clamp screw . . . 🙂