I bought a 255 Sprint from a buddy. It used to have a 48hp rude. It now has a rebuilt 1992 70 hp Johnson.Tach said 7100 rpm, but I know it's not turning that much. What position should the pulse screw be set for this 3 cylinder engine(it has 5 different positions)??? The prop that's on it is a 13X17. It shows almost 6000 wot trimmed all the way down also. thanks