SE216 (Replaces most Mercury 3.0L) 90-216 Replaces Most Mercury 3.0L Lower Units with 13 Splines and 20,25, and 30 inch Shafts. If you have an 8 Spline drive shaft you will need to buy the stub shaft unit and purchase an upper driveshaft from an OE dealer. 20" 45-824114A 1 25" 45-823901A 1 30" 45-824115A 1 If you have a 13 spline two piece shaft just purchase the appropriate one piece shaft from the drop down box.