1998 Johnson Evinrude EC 50 thru 70 HP 3-Cylinder Service Manual, Page 181Get this manual
Cleaning and Inspection 1Clean all parts with parts cleaning solvent and dry with compressed airAll nut and screw threads coated with OVIC Screw Lock or OVIC Nut Lock must be thoroughly cleaned before assemblyWhen using thread locking product, be sure to prime the threads with OVIC Locquic Primer2Discard all seals, a-rings, and gaskets3Examine the upper and lower thrust mounts, and replace if deteriorated or damaged4Before checking the exhaust housing for distortionthoroughly clean the top and bottom mating surfaces and remove all sealer and corrosion00
5Check the exhaust housing for distortionPlace the housing on surface plateUsing dial indicator, check flatness by measuring the run-out on the top edge of the housingThe maximum allowable run-out is 0.009 in(0,228 mm)If you do not have access to dial indicator and surface plate, seek the services of machine shopDO NOT attempt to straighten distorted housing; replace itdistorted exhaust housing will cause the upper driveshaft splines to wear excessively and will damage the crankshaft splines6Inspect the water tube for obstructions or kinks, which may restrict water flow