Part Number: IM150

Upper Gear Set 1.50:1

Gear set for Mercruiser upper drive.FITS MERCRUISER #1 1971 & Alpha to 1996

LOWER Bearing FOR driven gear is different and included

Fits most V-8, ratio determined by 20/22 teeth count

Part Number: IM165

Upper Gear Set 1.65:1

Gear set for Mercruiser upper drive shaft housingMercruiser #1 1971 & Alpha to 1996 (press on gears)

If you seea nut under your top cap these will not fit

Your drive shaft should have 13 splines not 8

Ratio determined by teeth 24/24

Part Number: IM184

Upper Gear Set 1.84:1

Gear Set for Mercruiser upper drive shaft housingMercruiser #1 1971 Alpha to 1996 (press on gears)

If you see a nut under your top cap these will not fit

Your drive shaft should have 13 splines not 8

ratio determined by teeth 19/17

Part Number: IM198

Upper Gear Set 1.98:1

Gear set for Mercruiser upper drive shaft housingMercruiser #1 1971 & alpha to 1996 (press on gears)

If you see a nut under your top cap these will not fit

Your drive shaft should have 13 splines not 8

Ratio determined by teeth 24/20