1991 Johnson/Evinrude Models "EI" 40 thru 55 Service Manual, Page 307Get this manual
General Safety Warnings
Before returning motor to owner, verify that manual release valve is torquedReplace any locking type fastener (locknut or patch screw) if its locking feature becomes weakDefinite resistance to tightening must be felt or locking fastener is not suitable for continued useReplace only with authorized replacement part or equivalentWhen servicing this hydraulic unit, only use the service procedures outlined and the correct parts catalog for this specific unitSome internal components may appear similar to those in other hydraulic units but may have different operating pressures and characteristicsInterchanging these components may have an adverse effect on the unit's operationBe sure the thrust rod is correct adjustedThis will prevent the possibility of loss of boat control should the motor trim "in" too far