I actually have couple questions in this post but mainly to get me the right prop for my boat. First off it is 1990 sweet 16 classic. It has alpha drive and merc 4.3l v-6 in it. It also has performance corsa through hull exhaust on it. my first question would be anybody know what gears i have in the drive (ratio) . I just bought the boat and its got a 21p prop on it. Took it out today for first time and the boat is running about 52mph on the speedo. I am going to try to gps in couple days cause it def. feels like its wrong. Anybody the boat should be doing mph wise with that prop on it? it almost feels like the prop is slipping and not making the boat move enough( too high rpm) My main thing is running at the speed on the speedo 52mph i am tached at like 5500 to 5800. which i think is way to high for that motor. I have seen guys sayig 23p is the way to go. I am looking to gain a bit more speed but lower my rpms. (i might be running higher speeds and speedo is wrong) Somebody help me out here with some suggestions thanks...