1990 Johnson Evinrude "ES" 40 thru 55, P/N 507872, Page 219Get this manual
Driveshaft Shimming Using Tool PI 393185 The driveshaft pinion is precisely meshed with the forward and reverse gears by the use of shim or shims between the driveshaft bearing housing and thrust washer When installing new thrust bearing or washer, bearing housing, pinion, or driveshaft, it is necessary to gauge and select the proper shims to restore factory clearanceGauge bars are precision made and should be handled carefullyThe length of each gauge is stamped near the part number, and this dimension can be used to measure the gauge to confirm accuracyThis dimension is 0.020 in (0,508 mm) shorter than the actual shimmed length of the driveshaft INote Before assembling the pinion to the driveshaft, degrease