ok guys, here's the deal-
My boat is an '80 glastron cvx18 with a mercruiser 228 (305 chevy 4bbl). When i bought the boat about 3 years ago, it would run around 4800 rpm w/ a 21 pitch going about 55-60 mph. at some point it lost power and i am now down to 4500 rpm w/ a 19 pitch going about...