i am looking for the correct gear ratio for my setup 1986 350ci ,260 hp,alpha one outdrive . i have a 1.50 gear in it now,but only get 4100 rpm and 38 mph with my 21"pitch clever prop which came with boat,i did have 4800 rpm , and 49mph with first alpha drive that came with boat. please let me know which gears i need and or what could be wrong thanks bob.call me 1 516 754 1763.