"In 1981 the marine industry went from powerhead rating to a prop rating. The word was that the Japanese engines of the same rating were outperforming the US engines, as they were rated differently. To get the equivalent prop HP on a US motor prior to 1981, take the HP rating & subtract about 10%, this will get you close to the newer rating."<br />From:<br /> http://www.pugetsoundanglers.org/Fishing Info/Johnson 9.9_15.htm <br /><br />So I guess you have 15 hp at the prop
Back in 1962, I remember a promotional film that OMC had out. At that time Mercury was considered a major competitor and OMC made a point that the horsepower of their engines were rated at the propeller whereas Mercurys horsepower was rated at the powerhead. Confusing issue at times!
