1977 Evinrude 4HP Outboards Service Manual, PN 5303, Page 24Get this manual
To assure that the fuel tank contains the proper mixture, drain and flush the tank at least once year, and at every tune-up or major repairClean the tank by flushing with clear gasoline or solventPrimer, screen, etc, may be inspected and cleaned as described belowRefill the tank with the correct fuel mixtureDESCRIPTION The fuel tank is of simple but rugged construction, with capacity of gallons of fuel mixtureIt contains the bulb primer (for priming the fuel pump), fuel hose and connector, bracket arrangement to hold fuel line when not in use, carry grip, and disc valve which prevents any escape of gasoline or fumes, minimizing the danger of explosion or fireSee Figure 3-18BULB PRIMER DISC VALVE
from escapingTo check operation of the valve, alternately blow into the valve and draw outAir should enter but not escapeValve assembly can be serviced by unscrewing from tankSee Figure 3-20_ _-SEAT
Figure 3-20
Fuel Tank Vent Assembly (Serviced as assembly only)
HOSE AND PRIMER BULB ASSEMBLY CLAMPS To disassemble hose clamps, grip clamp with pliersBend overlapping hook backward (in direction of arrow) to release clampSee Figure 3-21To assemble hose clamps, grip clamp firmly with pliersApply slight pressure to hook on topside with screwdriverSqueeze clamp with pliers until hooks interlockSee Figure 3-22