Sierra 18-9855 Mercruiser Driven Gear Shimming Tool Measures upper DRIVE gear clearance on MC-I, R-MR, Alpha One and Alpha OneGen. Two drive units. Interchangeable with GLM 90170 Mercury Marine 91-60523 Application Mercruiser Stern Drive Alpha One Gen II 1998-1998 sn 0L100040 up California Residents WARNING Cancer and Reproductive Harm - P65Warnings.ca.gov Other Details Google Product Type Special Tools Wiser Yes Product MPN 18-9855 Product UPC 808282109639 Fast Ship In Stock Ships Today Deals