1999 "EE" 90, 115 FFI, 150, 175 V4, V6 FFI Outboards Service Manual, P/N 787024, Page 121Get this manual
2Inspect the intake manifold: All gasket surfaces must be smooth and free of nicks []J
Use machinist's straightedge to check flatness in all directionsSurface must be flat, 0.004in(0,10 mm)
All manifold components must be clean before assemblyDo not use strong carburetor cleaner or hot soaking tank
Assembly
1Place leaf valves on leaf plateIf new valves do not seat on the leaf plate, turn the leaf valves overUsed leaf valves must not be turned over for reuse Leaf valve may break, causing serious powerhead damage
2If any leaf valves are standing open, apply light pressure using pencil eraserIf leaf valve closes with light pressure, valve is acceptableIf not, inspect leaf plate for high spots or burrs