1997 Johnson Evinrude "EU" 40 thru 55 2-Cylinder Service Manual, P/N 507265, Page 74Get this manual
Disassembly
1Remove primer pump housing retainer from primer pump2Remove primer plunger from housingDiscard O-rings
Inspection
Inspect brass plunger shaft for any burrs or scratchesRemove small scratches by polishing the plunger with crocus clothIf the plunger has deep scratches, replace the plungerInspect plunger where cross hole intersects inside holeAny burrs around cross hole will accelerate wear of O-ringsRemove any protruding burrs, and polish with crocus clothThe check valve under the small nipple on the primer pump housing allows fuel flow .out of the pump housing and prevents flow into the housing
To verify check valve function, connect clear plastic hose between the small nipple and syringe filled with isopropyl alcoholSqueeze the syringe lightly to force alcohol through the hoseVisually check for alcohol flow into the housingIt is permissible for few drops to enterThis indicates the check valve is blocking the flow and functioning correctlyIf steady stream of alcohol flows through the small nipple, the check valve is inoperative and the primer pump housing must be replacedInstall hose between the large nipple of the primer pump housing and the syringePlace your thumb over the end of the plunger housingSqueeze the syringe to fill the plunger housingAlcohol should flow freely out of the small nipple, indicating no obstructionsIf no flow is indicated, replace the primer pump housing