Sierra 18-2167 Engine Drive ShaftReplaces part number 45-41939A1For all #1 units S/N 2791957 & above except MR/Alpha units or units which have been retro-fitted with MR/Alpha lower units. Also for 165 (6 cyls) S/N 2763442 & above.Interchangeable with: GLM; 11110; Mercury Marine; 45-41939A1; Application:Mercruiser Stern Drive R/MR/Alpha One (Sterndrive); 1983-1991; s/n 6225577 thru 0D469858; R/MR/Alpha One (Transom Assembly); 1983-1991; s/n 6216687 thru 0D469858;