ok i have a 350 chevey with a omc 800 stringer outdrive i just changed my omc outdrive upper from a v-8 gearing to a v-6 geared upper the old unit had 21:16 ratio and the new upper has a 21:20 so is geared higher if you will i ran the boat today and with an aluminum 14 1/2 x 19p prop the engine...