New 383 MAG Inboard 4V – a perfect repower for all Bertram 28, 31 & 35s

Finally, the perfect engine to replace a 5.7 litre or 7.4 litre classic inboard!

Not only is MerCruiser’s new 383 MAG Inboard 4V powerful and lightweight, it also comes

in standard and opposite rotation versions – making it an ideal repower option for many boat owners.

“For example, there are a lot of people with older 28, 31, 35 Bertrams who are still running their original, tired engines,” said David Meehan, Director of MerCruiser (Australia, New Zealand, Pacific).

“The 383 MAG Inboard is the perfect answer. It’ll be like having a new boat, guaranteed, at a lot less cost.”

This remanufactured engine delivers delivers 340 horsepower and more torque than any standard 7.4L big block.

And it does so while weighing some 70 kilograms less.

“It is compact as well, so it will fit into the existing engine bay without any costly engineering,” David said.

And the option of standard and opposite rotation versions means there’s no need to install a new transmission for twin engine applications.

The 383 MAG also has a full roller valve train which reduces friction and saves on fuel.

All MerCruiser Remanufactured engines come with a 1-year factory backed limited warranty.


Horsepower @ flywheel


Kilowatts @ flywheel


Maximum RPM (WOT)



Remanufactured GM V8 Marine Iron Block & Gen+ Heads – 062 Casting

Displacement (CID/L)

383 / 6.3

Bore & Stroke (in/mm)

4.03 x 3.75in
102 x 95mm

Compression Ratio

9.0:1 with Hypereutectic Pistons

Fuel Requirement

87 octane (R+M)/2

Engine Control System

Thunderbolt V w/Knock Control – MIE Calibration

Fuel Delivery System

4V carburettor and mechanical fuel pump

Fuel Injection System / Carburettor Type

750 cfm Weber 4V with electric choke

Induction System

Dual Plane Aluminium Intake Manifold with Bronze Inserts

Charging alternator amp


Charging alternator watt


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

Recommended Oil

SAE 25-40 NMMA Certified FC-W Synthetic Blend

Rocker Arms

1.6:1 Full Roller Aluminium

Length (in/mm)

43in / 1092mm

Width (in/mm)

29in / 737mm

Height (in/mm)

22in / 559mm

Weight (lbs/kg)

980lbs / 444kg – When Installed with 72C Transmission

Features & Related Products

Audio Warning System:
– Oil Pressure
– Coolant Temperature
– Transmission Temperature