Need Prop Help... 140/Looper on a Bracket
 

I have a 1979 V-20 ...I repowered it from an I/O to a Gil Bracket with floatation... Installed a 1988 Johnson 140HP VRO Looper .....It has a 13 1/4" X 17P aluminum prop on it, Cavitation plate is 2 1/2" above the bottom of hull... My V-20 is heavier than most with lots of gear and fishing equiptment and a hard top... Motor runs great but seems to have way to much prop on it the tach was broken. . I just installed a new tach.....I'm wondering if anyone can recomend a starting point for prop size I'm thinking 13 1/4 X 15p or even a 14p.....

do you have the small V4 style gearcase or do you have the big V6 gear case, they were avbailable both ways

how far back is your motor set? the correct height is for every 1 ft back from transom to the lower unit your cav plate should be 1 inch above bottom of the boat. is it a 20 or 25 inch motor? if it's a 20 inch you will have the small gear case, is it a 13 or 15 spline prop shaft? if it's a 13 spline then the 13 1/4 x 15 in stainless would be a good prop. if it's the 15 spline larger v4 lower unit then a 15 x 15 would be a good place to start.

What is your WOT reading on the new tach? By "too much prop" I take it you think the motor is not reaching it's proper RPM @ WOT? If that's the case I'd keep the same dia if possible and drop to a 15p prop for starters.. Dial in the pitch first, then fine tune with different diameters if necessary. IMHO

Being an 88 it is probably a V-4 gearcase regardless of shaft length. A 13 1/4 X 15 stainless would be a good starting point as the 17 is quite a bit of prop for one.