The way I read that document, you round after you multiply. (Assuming I read it correctly, and that document is correct) Which, combined with a narrower transom than beam, would account for the ~50hp difference between the two calculations.
19.66 * 7.5 =147.45 or 147.0 rounded. Which then gets a 205 hp rating, because 147*2-90= 204 and rounds to 205hp.
Rounding both gets 20 * 8 =160.0 Which gets a 230hp rating
Rounding after, and using a 6.75 foot transom width gets:
19.66 * 6.75 = 132.705, rounds to 133.0. 133*2-90 gets 176hp, rounded to 180hp. My guess is that this is close to how it was calculated for the original capacity plates.
|