Drive Unit chart

Sterndrive model/Year guide

Please use the table below to help you determine the correct model sterndrive, Upper or lower half.

***We will also require you to enter the year and horsepower of your MerCruiser in the "Special Instructions" area of checkout. This will help us confirm the correct application for you.

While this guide should cover most models there may be other models not listed here. If you have any questions regarding a particular application or are unsure please give us a call at (877) 567-8930 or email us

Sterndrives and lower units are available in counter-rotation as well.
Counter rotation is typically used on the Port side of a twin engine boat.
Older inline engines may use a shorter (8-1/8") U-joint spline shaft, click here for help.
Frequently asked questions, click here.
Applications may also be affected by boat operating altitudes, twin engine applications, special configurations. Just give us a call and we'll help!

Sterndrive Model	HORSEPOWER / Model	ENGINE / Old Gear ratio	YEAR	NEW RATIO & Gear Teeth	Choose Below
Merc. #1, 120-260, "Pre-Alpha"	120, 140	4 cyl. One drive /1.98:1	1972 thru 79	1.94 / 20-24	Complete drive (short shaft) Complete Counter (short shaft) Upper half (short shaft) Lower half Lower half counter
Merc. #1, 120-260, "Pre-Alpha"	170, 190, 470, 485, 490, 3.7 Liter	4 cyl. One drive /1.84:1	1972 thru 79	1.81 / 17-19	Complete drive (short shaft) Complete Counter (short shaft) Upper half (short shaft) Lower half Lower half counter
Merc. #1, 120-260, "Pre-Alpha"	165	6 cyl. /1.65:1	1972 thru 79	1.62 / 24-24	Complete drive (short shaft) Complete Counter (short shaft) Upper half (short shaft) Lower half Lower half counter
Merc. #1, 120-260, "Pre-Alpha"	188, 198, 228, 260	V-8 /1.32:1 or 1.50:1	1972 thru 79	1.47 / 20-22	Complete drive Complete Counter Upper half Lower half Lower half counter
Merc. #1, "R" drive, 120-260, "Pre-Alpha"	120,140, 2.5, 3.0 Liter	4 cyl. One or "R" drive /1.98:1	1980 thru 84	1.94 / 20-24	Complete drive (short shaft) Complete drive (std. shaft) Complete Counter (short shaft) Complete Counter (std. shaft) Upper half (short shaft) Upper half (std. shaft) Lower half Lower half counter
Merc. #1, "R" drive, 120-260, "Pre-Alpha"	170, 190, 470, 485, 490, 3.7 Liter	4 cyl. One or "R" drive / 1.84:1	1980 thru 84	1.81 / 17-19	Complete drive (short shaft) Complete drive (std. shaft) Complete Counter (short shaft) Complete Counter (std. shaft) Upper half (short shaft) Upper half (std. shaft) Lower half Lower half counter
Merc. #1, "R" drive, 120-260, "Pre-Alpha"	165	6 cyl. One or "R" drive /1.65:1	1980 thru 84	1.62 / 24-24	Complete drive (short shaft) Complete drive (std. shaft) Complete Counter (short shaft) Complete Counter (std. shaft) Upper half (short shaft) Upper half (std. shaft) Lower half Lower half counter
Merc. #1, "R" drive, 120-260, "Pre-Alpha"	188, 198, 200, 228, 260, 5.0 & 5.7 liter	V-8 One or "R" drive /1.50:1	1980 thru 84	1.47 / 20-22	Complete drive Complete Counter Upper half Lower half Lower half counter
Alpha One (Gen. One)	120, 140, 3.0, 3.0 LX	4 cyl. / 1.98:1	1985 thru 90	1.94 / 20-24	Complete drive Complete Counter Upper half Lower half Lower half counter
Alpha One (Gen. One)	170, 190, 470, 485, 490, 3.7 Liter, 3.7 LX	4 cyl. /1.84:1	1985 thru 90	1.81 / 17-19	Complete drive Complete Counter Upper half Lower half Lower half counter
Alpha One (Gen. One)	198, 5.0, 5.0 LX	V-8 / 1.65:1	1985 thru 90	1.62 / 24-24	Complete drive Complete Counter Upper half Lower half Lower half counter
Alpha One (Gen. One)	260, 5.7, 5.7 LX	V-8 /1.50:1	1985 thru 90	1.47 / 20-22	Complete drive Complete Counter Upper half Lower half Lower half counter
Alpha One (Gen. One)	454 Magnum / 330 HP �	V-8 / 1.32:1	1985 thru 90	1.47 /20-22	Complete drive Complete Counter Upper half Lower half Lower half counter
Alpha One (Gen II)	3.0, 3.0 LX	4 cyl. / 1.98:1	1991 thru present	1.94 / 20-24	Complete drive Complete Counter Upper half Lower half Lower half counter
Alpha One (Gen II)	4.3, 4.3 LX	V-6 / 1.84:1	1991 thru present	1.81 / 17-19	Complete drive Complete Counter Upper half Lower half Lower half counter
Alpha One (Gen II)	5.0 (twin engines)	V-8 /1.65:1	1991 thru present	1.62 / 24-24	Complete drive Complete Counter Upper half Lower half Lower half counter
Alpha One (Gen II)	5.7, 5.7 LX	V-8 / 1.50:1	1991 thru present	1.47 / 20-22	Complete drive Complete Counter Upper half Lower half Lower half counter

� Please Note: Our Sterndrives are covered under warranty for engines up to 300 horsepower. Sterndrives are available for engines over 300 horsepower however they will be sold without warranty.