Guide to Marine Shoreline Leads and Connectors

For simplicity, the term 'boat' is used in this guide to refer to any type of vessel e.g. yacht, leisure craft, canal boat.

What is a shoreline power connection?

Many boats are fitted with a power inlet, which enables a shoreline cable to connect it to a mains electricity socket at a mooring. The electrical connection can be used for a myriad of applications from trickle charging engine batteries, to powering domestic appliances. 

How can I tell which type of power inlet is fitted to my boat?

Power inlets fitted to small boats in the UK and Europe are most commonly rated at 230v 16A. Unfortunately, there are four different designs of connector, with no cross-compatibility between them. 

The guide below shows the range of connectors used within the UK and Europe. As identification labels are often missing or unreadable, key dimensions have been included.

We provide the highest quality shoreline cables made in our UK workshop from marine grade cable, together with a wide range of replacement connectors

Boat Inlet


Shoreline Lead Socket 

IEC60309 'Commando' 

230v 16A

IEC60309 230v 16A socket, commonly referred to as a Commando or CEE connector.

This is the most common connector used across the UK and Europe for small boats.

Note that in contrast to the Victron connector below, the plastic around the boat inlet protrudes outwards and is 43mm diameter. The shoreline socket is recessed inside the blue shell, with an outside diameter of 49mm.

230v 32A and 63A

Larger 32A (57mm diameter) and 63A versions (69mm diameter) are also available.


The terminals are marked:

  • Live = L
  • Neutral = N
  • Earth = E or the earth symbol 

Boat Inlet


Shoreline Lead Socket

Victron Energy/Ratio 

250v 16A

The same connector is marketed under the brand names Victron Energy and Ratio Electronics.

At first glance it can appear the same as the commando connector, as the pins are an identical size and configuration. However, the two types are not cross compatible. In contrast to the commando connector, the pins in the boat inlet are recessed inside. The shoreline socket part protrudes from the outer yellow shell and is 39.5mm in diameter.

250v 32A and 50A

Larger 32A (50mm diameter) and 50A (52mm diameter) versions are also available.


The terminals are marked:

  • Live = L1
  • Neutral = N
  • Earth = Earth symbol

Boat Inlet


Shoreline Lead Socket


230v 16A

The Marinco is the European version of the most popular connector in Northern America. The connector has flat blades, pushes in and then twists to lock.

The connector will be marked 230v 16A, although it is actually based on the NEMA L5-30 design.

The white section of the shoreline socket is 45mm in diameter and protrudes by 19mm, far less than the Hubbell. The outside diameter of the blades in the boat inlet is 25mm.

230v 30A

A larger 30A (50mm diameter) version is available. The outside diameter of the blades in the boat inlet is 29mm. There are also a myriad of 125v versions used in North America.


The terminals are identified:

  • Live = Brass/black screw, brown marking
  • Neutral = Silver screw, blue marking
  • Earth = Green screw and marking

Boat Inlet


Shoreline Lead Socket


230v 16A

The Hubbell connector is also the European version of a connector used in Northern America. The connector has flat blades, pushes in and then twists to lock.

The connector will be marked 230v 16A, although it is actually based on the NEMA L6-20 design.

The white section of the shoreline socket is 46mm in diameter and protrudes by 35mm, much further than the Marinco. The outside diameter of the blades in the boat inlet is smaller than the Marinco at 23mm.


The terminals are identified:

  • Live = Brass/black screw or marked Y
  • Neutral = Silver screw or marked X
  • Earth = Green screw


What is a Shoreline Power Point?

Electricity is normally provided at marinas and other moorings using power bollards. In addition to sockets, the bollard will have a clear window with a circuit breaker and RCD. What do they actually do?

Shock Protection

Each socket must be protected with an RCD. An RCD, or residual current device, is a life-saving device which is designed to prevent you from getting a fatal electric shock if you come into contact with a live wire or object. 

An RCD constantly monitors the electric current flowing through the live and neutral wire. If a fault occurs and the live and neutral current become unbalanced (e.g. someone has come into contact with a live wire), the current will flow to earth and the RCD will detect this fault and cut the power immediately.

This useful YouTube video helps explain how an RCD works.

Overload Protection

Each socket must also have overload protection provided by a Miniature Circuit Breaker (MCB). MCBs trip and cut off the power if too much current flows through a circuit or there is a short circuit. Unlike RCDs, they do not protect against the risk of electrocution, as the current required for them to trip would not be generated in such a situation. MCBs protect property, RCDs protect people. 

More recently RCBOs have become more widely used. They are a single unit providing the combined function of an RCD and MCB.

How can I tell which type of socket is available at the mooring?

The most common socket at marinas across the UK and Europe is the blue IEC 60309 commando 230v 16A. The socket has 3 contacts and is single phase (it has 1 live contact L+N+E). A standard boat shoreline cable with an IEC 60309 commando 230v 16A plug can connect directly to the socket.

Marina Socket Plug Required


230v 16A IEC 60309

  • Blue
  • 43mm diameter
  • 3 pins


Other sockets may be available for larger boats. The most common is the blue 230v 32A commando socket, which has larger pins and overall diameter to the 16A version. 

Marina Socket Plug Required


230v 32A IEC 60309

  • Blue
  • 57mm diameter
  • 3 pins


A standard shoreline lead with a 16A plug must not be connected directly to the 32A socket by either swapping the shoreline lead plug to a 32A version or using a simple adaptor. Despite being dangerous, adaptors like the one below are often sold by unscrupulous online suppliers:

The only safe way is to use an adaptor fitted with a 16A MCB (circuit breaker). Without a 16A MCB, the lead and boat installation will only be protected by the 32A circuit breaker from the supply. In the case of a fault, wires could become dangerously hot, even causing an electrical fire, before the 32A MCB trips. A suitable safe adaptor is available here

In the rare case that only red 415v three phase IEC 60309 sockets are available, these can be used with a suitable adaptor. Whilst the socket has 3 live contacts (hence three phase), the voltage between each phase (live) and neutral is 230v. For 415v 16A sockets a simple adaptor cable is required, whilst with 32A sockets an adaptor with a 16A MCB is essential.

What's a shoreline cable?

A shoreline cable is the cable used to connect the boat to the marina power supply. Using the tables earlier in the guide, you should be able to identify the correct connector for the inlet on the boat and the right plug for the marina socket.

We provide the highest quality shoreline cables, made in our UK workshop from marine grade extremely robust orange rubberised cable and available with a range of connectors.

Cable Diameter

The IET Wiring Regulations (BS 7671) specify the cable diameter required for shoreline leads; this refers to the size of the inner cores, not the overall diameter of the cable itself. Cables with 16A connectors require 2.5mmsq, whilst those with 32A connectors require 6mmsq. When it comes to shoreline cables, the correct diameter is important.

Imagine watering your garden with a 20m hose pipe. The hose pipe exerts resistance on the flow of water. The longer the pipe, the more resistance is experienced by the water as it flows through, resulting in lower the pressure at the end. This same principle applies to electricity flowing through a cable. The longer the cable, the more resistance is exerted on the flow of electricity. Just like the pressure is reduced at the end of a long hose pipe, voltage is reduced at the end of a cable. The smaller the diameter of the cable, the more the voltage reduces with each metre. As the voltage drops, appliances draw more current to compensate, resulting in reduce performance and risk of overheating.

Cheap cables, particularly those under 14m, are often sold using 1.5mmsq flex. They do not comply with the IET Wiring Regulations (BS 7671) requirements for shoreline cables and should not be used.

Cable Length

Leads should be kept to the minimum length required. Under no circumstances should a lead be coiled either in open air, or on a reel when in use. Using a lead which is still coiled, can lead to the build up of heat, with catastrophic results.

Cable Types

Orange Rubber H07BQ-F

We only use orange rubber H07BQ-F cable with our marine leads and meters. It is an industrial specification marine grade cable, specifically designed for use in harsh environments. It benefits from a high resistance to mechanical, chemical, water and UV damage. Flexibility and performance is retained over a wide temperature range (-40 to 90°C). 

The cable has a silicone appearance and is exceptionally tough. Whilst at a distance it looks similar to artic cable, it is in an entirely different league. Whilst the cost per meter is higher, it should provide a significantly longer service life 

Arctic Cable

Blue ‘arctic’ flex is commonly used for shoreline leads. Yellow arctic cable was originally designed for 110v construction site use, where it offered flexibility down to -25°C. Whilst a blue 230v version is available, it is not tested to the same standards and is not recommended for use below 5°C.

Compared to H07BQ-F cable, it is far more prone to mechanical and UV damage. We therefore do not consider it suitable for marine applications. Further information on the significant limitations can be found in this excellent article within Wiring Matters.

CY ‘Flexible Armoured’ Cables

CY cable is sometimes used for shoreline leads, in the mistaken belief that it is a tougher cable. However, it is entirely unsuitable for use in the marine environment. The PVC sheath is not specified as waterproof, it has low UV resistance and should not be used for prolonged periods outside. The sheath is prone to mechanical damage and becomes stiff at colder temperatures. The wire braiding is not intended to be used for mechanical protection, it is purely for screening.

How do I Connect to Shoreline Power Safely?

The IET Wiring Regulations specify the wording of a sign to be placed by all marine shoreline sockets, which provides useful advice:

On Arrival

  • Ensure that the supply is switched off before inserting the craft plug.
  • For safety reasons, your craft must not be connected to any other socket outlet than that allocated to you and the internal wiring on your craft must comply with the appropriate standards.
  • Every effort must be made to prevent the connecting flexible three-core cable from falling into the water if it should become disengaged. For this purpose, securing hooks are provided alongside socket outlets for anchorage at a loop of tie cord.
  • Only one leisure-craft connecting cable may be connected to any one socket outlet.
  • The connecting flexible cable must be in one length, without signs of damage, and not containing joints or other means to increase its length.
  • The entry of moisture and salt into the leisure-craft inlet socket may cause a hazard.  Examine carefully and clean the plug and socket before connecting the supply.

Before Leaving

  • Ensure that the supply is switched off before the connecting cable is  disconnected and any tie cord loops are unhooked.
  • The connecting flexible cable should be disconnected first from any marina socket outlet and then from the leisure craft inlet socket.  Any cover that may be provided to protect the inlet from the weather should be securely replaced.  The connecting flexible cable should be coiled up and stored in a dry location where it will not be damaged.

Our Additional Advice

  • Carefully check the cable condition prior to each use and replace if it shows signs of damage.
  • Regularly check the contacts of the lead plug and socket, together with the boat inlet for signs of corrosion or over heating. Pin/blade corrosion can cause a poor electrical connection, leading to overheating. Heat damage will cause the metal to turn darker, often with a multicoloured pattern. The plastic may also be melted, particularly around the contact.
  • Ensure the cable is fully uncoiled to avoid the risk of overheating
  • When not in use, store cables safely, away from sharp edges, sea water or other contaminants. We offer a range of cable storage solutions.

How can I measure the electricity I use?

In response to customer demand for a reliable, robust weatherproof kWh meter suitable for marine use, we developed our own unit. Manufactured in our UK workshop, they combine a high quality shoreline cable with a digital MID certified class 1 accuracy meter.

A push button toggles the meter between displaying live power usage (W), resettable cumulative energy used (kWh) and non-resettable cumulative energy used (kWh).


Available either with 25cm cable either side to connect between a marina socket and a separate shoreline lead, or in 10m lengths with a range of connectors. Click here to see the range.


The latest IET Wiring Regulations (BS 7671) Eighteenth Edition Amendment 2 was published in 2022. Installations at marinas and moorings are covered within the special circumstances section 'Marinas and similar locations'. Electrical installations on boats are not governed by the IET Wiring Regulations. A range of different regulations apply, which must be followed. As a complex area, we always recommend consulting with a Marine Electrician.