1999 "EE" 90, 115 FFI, 150, 175 V4, V6 FFI Outboards Service Manual, P/N 787024, Page 50Get this manual
If vapor pressure increases due to hot fuel or high undercover temperatures, vapor volume expandsThe fuel level lowers, the float follows, and the vent valve opensVapor travels to the intake manifold, and as pressure drops, fuel level rises and the float closes the ventThis cycle repeats as conditions dictate, and thus eliminates hot fuel handling problems such as vapor lockTest Point
There is one test point for testing high pressureIt can be used to purge air from the fuel system to allow quick fillingThe test point can also be used to vent pressure prior to disassembly for service, and will allow installation of gauge to check system operating pressure&