Mercury-Mercruiser 8M0187373 Quicksilver Longblock 383 4V LH V8 Inboard

8M0187373 Quicksilver New Longblock Assembly 350 HP

GM 6.3 Liter Gen+ 383 V8
Left‑Hand / Standard Rotation
Replaces 2011‑2020 383 Mag Inboard (LH /standard rotation) Repower engines

3 Year limited factory warranty. No core or container deposit.

Parts that will need to be transferred or purchased separately:
• Balancer
• Flywheel
• Spark Plugs
• Distributor
• Water pump
• Manifold gasket set
• Quicksilver Synthetic Blend 25W‑40 4‑Stroke Oil

Black‑X Valve Technology
• 21N Intake valve parent material
• 24N Exhaust valve parent material
• Plasma nitride prevents valve sticking & increases toughness
• Chrome‑Cobalt alloy seats resist corrosion from alcohol fuels
• Valve life improved 42%
Hardened valve seat installed in the cylinder heads
• Hardened Intake & Exhaust seat inserts
• Premium alloy seat material
Heavy duty head and block castings
• Resist corrosion and cracking
• Higher loading capacity
• Ability to use solid engine mounts
Premium components
• 100% brass core plugs
• High volume oil pump
• Marine valve springs resist fatigue
• Super polished crankshafts using superior material and design features
100% Advanced SIM Testing
• Water and oil passages pressure tested 100%
• Phased rotational testing with hot oil validates all oil passages, bearings, and assembly
• Advanced compression testing verifies cylinder sealing and valve lash integrity
• Oil flush at completion of test removes break‑in debris
• Shipped without oil to prevent spillage while in transit