Manufacturer

ZEXEL Corporation (formerly Diesel Kiki Co., Ltd.)

Country of Origin

Japan

Product Type

Mechanical Hydraulic Governor

Marine Application

Main Marine Diesel Engines, Auxiliary Diesel Engines, Marine Generator Engines, Industrial Diesel Engines

Product Introduction

The ZEXEL RHD6-MC Hydraulic Governor is a precision mechanical-hydraulic speed governing system developed by Diesel Kiki (later ZEXEL) for medium and high-speed diesel engines. It automatically regulates engine fuel delivery to maintain a constant engine speed despite rapid load variations.

Widely used on commercial ships, fishing vessels, tugboats, offshore support vessels, and marine diesel generator sets, the RHD6-MC has earned a reputation for exceptional reliability, precise speed control, and long service life.

The governor operates using a hydraulic oil system combined with a centrifugal flyweight mechanism, providing smooth fuel rack movement and excellent stability under varying operating conditions.

SM MARINE SERVICE™ supplies New, Used, and Professionally Reconditioned ZEXEL RHD6-MC Hydraulic Governors, including repair services, calibration, overhaul, spare parts, and worldwide shipping.

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What is the ZEXEL RHD6-MC Hydraulic Governor?

The RHD6-MC is a self-contained hydraulic governor that maintains engine RPM by automatically adjusting the fuel injection pump rack according to engine load.

When engine load increases, the governor immediately increases fuel delivery to maintain speed. When the load decreases, it reduces fuel flow, preventing overspeed and ensuring stable operation.

Unlike fully electronic governor systems, the RHD6-MC operates using a mechanical flyweight assembly, hydraulic servo mechanism, and governor oil pump, making it highly dependable in harsh marine environments.

Main Features

• Genuine Japanese hydraulic governor
• Precision mechanical-hydraulic speed control
• Stable engine RPM regulation
• Built-in governor oil pump
• Adjustable speed droop
• High reliability
• Excellent transient response
• Long operational life
• Suitable for continuous marine service
• Easy overhaul and maintenance
• Proven design with worldwide marine applications

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Main Components

The ZEXEL RHD6-MC governor generally includes:

• Governor Housing
• Hydraulic Oil Pump
• Flyweight Assembly
• Hydraulic Servo Piston
• Governor Shaft
• Speed Adjusting Mechanism
• Droop Adjustment Assembly
• Compensating Adjustment Valve
• Bearings
• Oil Reservoir
• Control Lever
• Output Shaft
• Mechanical Linkage
• Seal Kit

Working Principle

The governor is driven directly by the engine gear train.

As engine speed changes, centrifugal flyweights move outward or inward according to RPM. This movement controls the hydraulic pilot valve, directing oil pressure to the servo piston.

The servo piston moves the fuel control linkage to either increase or decrease fuel delivery, maintaining the desired engine speed automatically.

This hydraulic feedback system ensures smooth engine operation with excellent speed stability during rapid load changes.

Marine Applications

The ZEXEL RHD6-MC is widely used on:

• Main Propulsion Engines
• Auxiliary Diesel Engines
• Marine Generator Sets
• Fishing Vessels
• Tug Boats
• Bulk Carriers
• Container Ships
• Offshore Support Vessels
• Passenger Ships
• Industrial Diesel Engines
• Harbor Power Units

Common Problems & Troubleshooting

Typical faults include:

Engine Speed Hunting

Possible causes:

• Incorrect compensating adjustment
• Air inside governor oil
• Internal wear

Oil Leakage

Possible causes:

• Worn oil seals
• Damaged gaskets
• Loose fittings

Slow Governor Response

Possible causes:

• Dirty hydraulic oil
• Blocked oil passages
• Worn servo piston

Unstable Engine Speed

Possible causes:

• Weak governor springs
• Flyweight wear
• Incorrect droop adjustment

No Fuel Control

Possible causes:

• Broken linkage
• Hydraulic pump failure
• Internal mechanical damage

Preventive Maintenance

To ensure long service life:

• Use the recommended governor oil.
• Replace oil according to maintenance intervals.
• Inspect for oil leaks regularly.
• Check linkage movement.
• Verify droop adjustment.
• Inspect bearings and seals during overhaul.
• Perform governor calibration after repairs.
• Follow manufacturer maintenance procedures.

Why Ships Continue Using the ZEXEL RHD6-MC

The ZEXEL RHD6-MC remains one of the most trusted hydraulic governors because of:

• Exceptional durability
• Proven Japanese engineering
• Reliable hydraulic operation
• Accurate speed regulation
• Easy field maintenance
• Long spare parts availability
• Excellent overhaul capability
• Wide compatibility with marine diesel engines

Frequently Asked Questions (FAQ)

Is the ZEXEL RHD6-MC still supported?

Yes. Spare parts, overhaul kits, and repair services remain available through specialized marine service providers.

Can the governor be repaired?

Yes. Most governors can be fully overhauled, including replacement of bearings, seals, springs, hydraulic components, and calibration.

Is calibration required after overhaul?

Yes. Proper speed and droop calibration are essential to ensure stable engine operation.

Does SM MARINE SERVICE™ supply this governor?

Yes. We supply New, Used, and Professionally Reconditioned ZEXEL RHD6-MC and RHD10-MC Governors, including spare parts, repair, calibration, and worldwide shipping.

Short Product Description

The ZEXEL RHD6-MC Hydraulic Governor (105856-5580) is a precision mechanical-hydraulic speed control unit designed for marine diesel engines and generator sets. Manufactured in Japan by ZEXEL (formerly Diesel Kiki), it provides accurate engine speed regulation, dependable performance, and long service life in demanding marine applications.

User Manual & Technical Resources

Typical technical documentation includes:

• User Manual
• Operation Manual
• Service Manual
• Workshop Manual
• Parts Catalogue
• Overhaul Manual
• Calibration Procedure
• Maintenance Manual
• Troubleshooting Guide

SM MARINE SERVICE™

SM MARINE SERVICE™ supplies New, Used, and Professionally Reconditioned marine governors, automation equipment, and genuine spare parts.

We provide:

• Worldwide Supply
• Governor Repair & Overhaul
• Calibration Services
• Genuine Spare Parts
• Technical Support
• Equipment Sourcing
• Fast Worldwide Shipping

Bangladesh Office
Samir Market, DT Road, Pahartali, Beside CDA Market, Chattogram, Bangladesh

China Warehouse & Support Center
Shanghai, China

Website
www.smmarineservice.com

Email
info@smmarineservice.com

WhatsApp
+8801818929292

Marketing Contact
Nazmul Hasan Bhuiyan