MERCURY MERCRUISER PCM 555 BIG BLOCK DIAGNOSTICS & TROUBLESHOOTING MANUAL #33 PCM 555 DIAGNOSTICS SN 0M000000 and ABOVE Models Covered in This Manual Sterndrive (MCM) Model Serial Number 496 MAG HO 0M000000 and Above 496 MAG 0M000000 and Above Inboard (MIE) Model Serial Number 8.1S HO 0M000000 and Above 8.1S Horizon 0M000000 and Above Service Manual Outline Section 1 - General Information Section 2 - Troubleshooting Section 3 - Wiring Diagrams