SE216 Lower Unit | SEI 90-216 Sterndrive Engineering SE216 Lower Unit | 90-216 SE216Replaces Most Mercury 3.0L Lower Units13 Splines20, 25, and 30 inch Shafts.If you have an 8 Spline drive shaft you will need to buy the stub shaft unitand purchase an upper driveshaft from an OE dealer.20" 45-824114A 125" 45-823901A 130" 45-824115A 1 (This item is no longer available from the OE. You will need to source a used one, or fix your old drive.)If you have a 13 spline two piece shaft just purchase the appropriateone piece shaft from the drop down box above.The SEI 216 gear cases are supplied with the correct water tube coupling for units with a serial number of OG438000 and higher. If your unit has a lower serial number, you will need to use your old water coupling or purchase the correct part (SEI part number 96-116-12K). If you need application assistance please email sales@macombmarineparts.com and have your engine serial number available. SE216 Installation Guide