383 MAG Inboard 4V 340HP


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29.00 (in)
22.00 (in)
43.00 (in)
Current Stock:

There is finally the perfect engine to replace a 5.7L or 7.4L classic inboard. This engine delivers more torque than any standard 7.4L big block, and it does so while weighing 150 pounds less. Standard and opposite rotation versions are available, so you don't have to re-engineer your classic boat with a different type of transmission to make it go again.

  • Full roller valvetrain reduces friction and saves on fuel
  • 1-Year Factory Backed Limited Warranty
  • Up to 2-Years of Mercury Product Protection Coverage available


Power 340 HP (254 kW)
Full Throttle Range 4600-5000 RPM
Displacement 383 CID (6.3L)
Engine Type Remanufactured GM V8 Marine Iron Block & Gen+ Heads - 062 Casting
Bore & Stroke 4.030" x 3.750" (102mm x 95mm)
Compression Ratio 9.0:1 with Hypereutectic Pistons
Rocker Arm Ratio 1.6:1 Full Roller
Fuel Requirement 87 Octane (R+M)/2
Fuel System Weber 750 cfm 4V Electric Choke Carburetor & Mechanical Fuel Pump
Induction System Dual Plane Aluminum Intake Manifold with Bronze Inserts
Ignition System Thunderbolt V with Knock Control - MIE Calibration
Charging System 65 Amp / 917 Watt Alternator
Water Drain System Multi-Point Drain - Hand Removable Blue Drain Plugs
Exhaust System Iron Manifold with Dry-Joint Exhaust Elbow
Cooling System Thermostatically Controlled Raw Water - 143F
Accessory Drive System Serpentine Belt
Lubrication System High Flow 100 psi Oil Pump and Copper Oil Cooler
Reccomended Engine Oil SAE 25-40 NMMA Certified FC-W Synthetic Blend
Audio Warning System

Oil Pressure, Coolant Temperature, Transmission Temperature

Dimensions (LxWxH) 43" x 29" x 22" - When Installed with 72C Transmission
Engine Weight (lbs./kg) 980 / 444 - When Installed with 72C Transmission
Boat Harness Type 14-pin with 10-pin adaptor included