Universal M3-20B Marine Diesel Engine

The Universal M3-20B is a compact, efficient, and dependable inboard marine diesel engine delivering approximately 20 HP, designed to provide reliable auxiliary propulsion for sailboats and small cruising vessels. Renowned for its simplicity and durability, the M3-20B is an excellent solution for boat owners seeking consistent performance and economical operation.

Engine Design & Construction

The M3-20B features a 3-cylinder, 4-stroke diesel configuration with mechanical fuel injection, ensuring smooth power delivery and dependable torque across the operating range. Built on a proven industrial diesel platform adapted for marine use, the engine is designed to withstand continuous operation in harsh marine environments.

A freshwater cooling system with heat exchanger helps maintain stable operating temperatures while protecting internal components from corrosion. Its compact dimensions allow for easy installation in tight engine compartments, and well-placed service points simplify routine maintenance.

Performance & Efficiency

Producing around 20 HP, the Universal M3-20B provides sufficient thrust for cruising, maneuvering, and docking. Its strong low-RPM torque makes it particularly well-suited for displacement hulls and auxiliary sailboat propulsion.

The mechanical fuel injection system promotes excellent fuel efficiency and reliability, keeping operating costs low while delivering steady performance during extended cruising.

Marine Integration

The Universal M3-20B is compatible with marine gearboxes and conventional shaft-drive systems, making it suitable for both new installations and repower projects. The balanced 3-cylinder design reduces vibration and noise, improving onboard comfort.

Ease of Maintenance & Reliability

Designed with simplicity in mind, the M3-20B offers easy access to filters, belts, and routine service components. Its straightforward mechanical layout reduces maintenance complexity and supports long service intervals. Supported by the Universal marine engine legacy, it benefits from reliable parts availability and service knowledge.

Ideal Applications

The Universal M3-20B Marine Diesel Engine is ideal for:

Sailboats and auxiliary propulsion systems
Small cruising yachts
Coastal and inland waterways
Owners seeking a compact, economical, and reliable marine diesel engine

Key Advantages

Proven Universal marine diesel reliability
Compact and space-efficient design
Fuel-efficient 3-cylinder diesel engine
Freshwater cooling with heat exchanger
Smooth operation with reduced vibration
Easy maintenance and long service life

Technical Specifications

General

Model: Universal M3-20B
Engine Type: 4-stroke, vertical, water-cooled marine diesel
Fuel System: Mechanical fuel injection
Aspiration: Naturally aspirated
Number of Cylinders: 3 inline

Displacement & Combustion

Displacement: Approx. 0.85–0.90 liters
Bore × Stroke: Approx. 72 mm × 73 mm
Combustion Chamber: Indirect injection diesel

Performance

Rated Power: Approx. 20 HP @ 3,000–3,200 RPM
Rated Speed: Up to 3,200 RPM
Torque Characteristics: Strong low-RPM torque for auxiliary propulsion
Fuel Consumption: Economical, dependent on load and propeller matching

Cooling & Lubrication

Cooling System: Freshwater cooling with heat exchanger
Lubrication System: Forced lubrication with gear-type oil pump
Engine Oil Capacity: Approx. 3.0–3.5 liters
Recommended Oil Type: Marine-grade diesel engine oil

Electrical System

Starting System: 12 V electric start
Alternator: 12 V marine alternator

Dimensions & Weight

Overall Dimensions (L × W × H): Approx. 780 × 460 × 550 mm
Dry Weight: Approx. 140–155 kg (engine only, excluding gearbox)

Drive & Installation

Rotation (Crankshaft): Counter-clockwise (viewed from flywheel end)
Drive Type: Inboard shaft drive
Compatible Gearbox: Universal marine transmission
Mounting: Flexible marine engine mounts

Service & Adjustment

Valve Clearance (Cold): Intake: 0.20 mm / Exhaust: 0.25 mm
Firing Order: 1 – 2 – 3
Maintenance Access: Easy access to filters, belts, and routine service points