Our new website is still in progress! For any enquiries please call +44 (0)1462 892391.
Download our product information sheets: Rope Cutters | Flexible Engine Mounts | Damper Drive Plates | Flexible Shaft Couplings | Clamp Half Couplings, Adaptors & Bobbins
UK Office Opening Hours: Monday - Friday: 8:00am - 5:00pm | Saturday & Sunday: Closed
Published on May 16, 2025
With marine engineering, every connection counts, especially when it comes to transmitting power between your gearbox and propeller shaft. This is where clamp half couplings come into play.
These vital components serve as the mechanical link that keeps propulsion systems functioning smoothly and efficiently.
Unlike their solid coupling counterparts, marine clamp couplings are designed to be maintenance-friendly, corrosion-resistant, and secure, even in the harshest saltwater conditions.
A poor fit or unreliable coupling can lead to misalignment, reduced efficiency, or even costly damage to your drivetrain.
If you’re fitting out a new engine installation or replacing a worn coupling, choosing the right one is crucial to ensure engine shaft alignment, long-term durability, and optimal power transmission.
A clamp half coupling is a precision-machined steel component that connects a marine gearbox output flange to a propeller shaft.
Unlike traditional solid couplings, which typically rely on grub screws and tight tolerances, clamp couplings use a clamping action to grip the shaft securely, accommodating standard tolerances with ease.
This makes them particularly useful for applications where quick adjustment, maintenance access, or shaft repositioning is important.
R&D Marine’s range of marine shaft couplings includes both imperial and metric sizes, ensuring compatibility with a wide variety of shafts and gearboxes.
If you’re dealing with PRM, ZF, Twin Disc, Hurth, or Volvo units, there’s likely a clamp half coupling in the range that fits the bill.
These couplings are available as solid or split styles, the latter allowing easier installation and removal without sliding the unit along the shaft.
The functionality behind clamp couplings lies in their name: they clamp firmly around the shaft using precision-machined bores, clamp bolts, and sometimes integrated keyways.
Here’s how it works:
Clamp half couplings are not limited to a single role, they’re integral across a wide range of marine systems, both in propulsion and auxiliary equipment. Their versatility and ease of installation make them a popular choice for professionals working with everything from compact leisure vessels to large commercial fleets.
The most common application for marine clamp couplings is in main propulsion systems, where the coupling connects the gearbox to the propeller shaft. This connection must handle continuous torque transmission, potential misalignment, and the harsh conditions of a marine engine room. A secure, correctly fitted coupling ensures smooth power delivery and reduces the risk of vibration-related wear.
In addition to propulsion, clamp half couplings are widely used in auxiliary machinery such as:
Clamp couplings are suitable for a wide range of vessels, including:
Choosing the right clamp coupling for your vessel isn’t just about size, it’s about performance, compatibility, and longevity. Below are the key factors to keep in mind when selecting a clamp coupling for marine use.
Clamp half couplings from R&D Marine are machined from high-quality solid steel, offering excellent strength and resistance to mechanical stress. For vessels operating in corrosive environments, such as saltwater or high-humidity regions, opt for marine-grade materials or ensure protective coatings are in place to enhance saltwater corrosion resistance.
Your coupling must be capable of handling the torque produced by the engine. R&D Marine’s steel half couplings cover a broad range of torque capacities, with ratings from 100 Nm to 10,000 Nm. Always consult manufacturer specs or a marine engineer to ensure proper match.
Couplings must match the shaft diameter and keyway profile to ensure a secure fit. R&D Marine supports both:
In marine environments, couplings are regularly exposed to moisture, salt, temperature fluctuations, and vibrations. Therefore, selecting corrosion-resistant couplings with robust design and protective finishes is essential. Consider options like split couplings for systems prone to vibration or needing frequent access.
In cramped engine compartments, especially on smaller boats or retrofitted vessels, split clamp couplings offer a real advantage. They can be fitted without sliding the coupling fully over the shaft, saving time, effort, and potential shaft disassembly.
Engine shaft alignment is critical to prevent wear on bearings, seals, and other drivetrain components. Clamp couplings allow for precise shaft positioning, which is especially important during installation or servicing. This reduces the risk of long-term drivetrain misalignment and promotes efficient operation.
Choosing the right marine clamp coupling involves more than matching shaft size. To ensure long-term reliability, proper alignment, and ease of maintenance, follow these essential steps:
Start by confirming your gearbox’s manufacturer and model, this is essential for determining the correct flange pattern, bolt-hole circle, and register size.
We offer an extensive catalogue of clamp half couplings and adaptors that are compatible with most leading gearbox brands.
If you’re unsure, our technical support team is here to assist in identifying the correct flange dimensions and pairing them with a suitable coupling.
Precision is important in terms of diameter. You’ll need to accurately measure:
Our couplings are available in both imperial and metric standards, adhering to:
To select a coupling that can withstand your system’s demands, we recommend checking:
Our clamp couplings are engineered to handle torque ratings up to 10,000 Nm, making them suitable for everything from small leisure boats to heavy-duty marine clamp applications.
Our couplings are available in standard flange sizes from 4″ to 7¼”, and we offer multiple options for:
Depending on your installation environment, you may require one of the following:
These are ideal for restricted spaces where sliding a coupling over the shaft is not practical. Our split clamp couplings are designed for quick installation and removal, minimising downtime.
A cost-effective choice for straightforward installations with easy shaft access. These offer dependable performance where space is not an issue.
If your gearbox flange doesn’t match the standard coupling, we offer custom-machined adaptors to ensure a precise fit. This is especially useful when switching between gearbox models.
Our precision-engineered bobbins are designed to extend shaft length when additional clearance or realignment is needed.
We offer standard sizes from 50 mm to 500 mm, with custom lengths also available upon request.
Every installation is unique, and we’re here to help you get exactly what you need. We offer:
All custom work is handled in-house by our skilled engineers, ensuring a fast turnaround and exact fit, no matter how complex the requirement.
Even seasoned engineers can overlook important considerations when selecting a clamp coupling for marine use.
Here are a few common pitfalls, and how to avoid them:
R&D Marine provides a comprehensive and versatile range of clamp half couplings and accessories, designed to suit the wide variety of configurations found across marine applications.
For outfitting a new engine or upgrading an older setup, their precision-engineered components ensure secure, high-performance results.
These robust couplings are machined from solid steel, offering exceptional strength and durability.
Their design accommodates normal shaft tolerances, allowing for a superior fit over traditional solid couplings.
Designed for ease of maintenance, split couplings are machined in two halves and bolted together, making them simple to install or remove, especially in confined marine engine bays where sliding a full coupling along the shaft is impractical.
When gearbox flange patterns differ from the coupling’s flange, adaptors are the perfect solution.
R&D Marine offers custom-machined flange adaptors to match various gearbox outputs.
Solutions that enable the use of flexible marine couplings where direct fitment isn’t feasible.
Bobbins are used to extend shaft length, offering flexibility for installations that require additional clearance or component alignment.
Precision-machined spacers are available in lengths ranging from 50 mm to 500 mm. They are used in conjunction with clamp half couplings and adaptors for full system integration
Especially valuable in tight engine bays or unique drivetrain layouts.
R&D Marine understands that not all marine coupling needs fit a standard mould. That’s why they offer in-house machining for bespoke projects, including:
With decades of experience, R&D Marine has earned its reputation as a trusted British manufacturer in the marine sector.
Our products are engineered to meet the real-world demands of both commercial and leisure vessels.
Here’s why industry professionals consistently choose R&D Marine:
Selecting the right clamp half coupling for marine applications is vital for ensuring safe, efficient, and long-lasting operation.
From material selection to shaft compatibility and space constraints, every factor must be considered to avoid unnecessary wear or downtime.
With a wide selection of clamp half couplings, split couplings, adaptors, and bobbins, R&D Marine makes it easy to find the right fit for your system configuration. Backed by custom engineering and fast, knowledgeable support, their solutions are trusted worldwide.
For expert guidance, always consult with a marine professional or contact R&D Marine directly to ensure you’re choosing the best coupling for your vessel.
If you’re looking for secure, high-performance marine couplings that stand up to harsh environments and demanding applications, look no further than R&D Marine.
Our range of precision-engineered clamp half couplings and split couplings are trusted by marine engineers, boat builders, and ship operators around the world. Whether you’re working on a new installation or retrofitting an existing system, we provide the components you need for reliable, long-term shaft-to-gearbox connections.
R&D Marine also supplies a complete suite of adaptors and bobbins, tailored to suit a variety of system configurations and gearbox models.
Explore our broader range of bespoke marine products, including:
Every component is designed to meet the highest standards of marine-grade durability, saltwater corrosion resistance, and ease of installation.
Don’t hesitate to call us today on 01462 892391 to discuss your requirements, check stock availability, or receive expert guidance on selecting the best marine coupling solution for your vessel.
A clamp half coupling secures itself around the shaft using a clamping action, offering a more uniform and reliable grip than a traditional solid coupling. It allows for better alignment, can accommodate normal shaft tolerances, and is easier to install or adjust.
In contrast, solid couplings depend on precise shaft tolerances and usually rely on set screws or keyways, which may not provide the same flexibility or holding strength.
For most marine applications, especially where reliability and serviceability are critical, clamp couplings for marine use are the preferred choice.
Not always. While some gearboxes share common shaft sizes, the flange bolt circle, hole pattern, and register diameter often vary between manufacturers.
If you’re replacing a gearbox or adapting an existing system, you may require a custom-machined adaptor to ensure compatibility.
R&D Marine offers a full range of adaptors to bridge different gearbox output flanges with the correct marine shaft coupling or flexible coupling. This ensures you get a secure, aligned fit without compromising system performance.
The choice between a split and solid clamp half coupling often comes down to access and maintenance requirements.
If you’re working in a confined engine room or retrofitting a system where it’s difficult to slide a coupling onto the shaft, a split clamp coupling is far more convenient. It comes in two parts and bolts together around the shaft, making installation much easier.
Solid couplings are more suitable for new builds or where full access to the shaft is available. They’re also a more economical option in straightforward applications.
