1988 Johnson Evinrude "CC" 9.9 thru 30 Service Manual, P/N 507660, Page 109Get this manual
Intake Manifold Servicing, 9.915 Removal 1Remove the powerhead as described in Section 4
Loosen and remove six intake manifold screws
3Remove intake manifold, leaf plate and two gasketsDiscard gasketsInspection
Inspect the leaf plate assemblies for damage: The leaf valves and plate must not be distorted The leaf valve tips must not be cracked or chipped The leaf stops must not be distorted or loose The check valve disk must be intact and free to move inside the valveThe check valve screen must be clean