I just bout a 1980 or 1981 Marquis Riviara with a Mercuiser 120 in it. The boat will pull up skiers but I want to get a little more hp out of it, is there any simple addition I can add to get that. I have tried a 15,75 x 15 pitch 4 blade prop, a 17 and 19 pitch 3 blade prop and all seem to...
