9.9 1987 Mercury fly wheel wont turn over

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I have a 1987 Mercury 9.9 with 50 hours of operation.Clean as a whislte inside Has not been run for 12 years. Fly wheel will not move.When manually disengage lock fly wheel turns. Handle shifter will not turn past neutral. Can I repair it myself? Or should I have it looked at by a outboard mechanic.