A deck crane is chosen by the load it must lift at its outreach over the ship’s side, not by the tonnage on its nameplate. Our 16 t telescopic deck crane lifts 16,000 kg only 2.5 m from its column, but at its full 22.3 m outreach it lifts 1,050 kg. Start with that outreach figure, then check the deck structure, the hydraulic power supply and the sea conditions in which the crane will normally operate.
This guide is for owners, builders and fleet managers who want to fit a hydraulic deck crane to a cargo vessel, landing craft, supply boat or workboat. It covers what a deck crane is and the main types. It shows how to measure outreach, how to stow the crane at sea, and how to mount and power it. For this guide we compiled the technical drawings and load charts of all 24 of our current marine cranes, from 0.8 t to 25 t, and every crane figure below is taken from them. Achord Chan, Product Operations Director at BOB-LIFT, compiled the guide from those drawings and from photographs and videos of our customers’ installations.
Key takeaways
- Size a deck crane by the load it must handle at your required outreach over the side; our 25 t knuckle boom deck crane, for example, lifts 2,000 kg at its full 18.0 m outreach.
- Telescopic deck cranes provide the longest outreach in our range: 22.3 m on the 16 t model and 22.0 m on the 20 t model.
- A knuckle boom folds into a compact envelope and keeps the cargo deck clear, whereas a telescopic boom needs a boom rest along the deck.
- The crane’s own weight ranges from 220 kg (0.8 t) to 6,950 kg (20 t telescopic), so the shipyard or naval architect must verify stability and deck strength.
- Load charts assume a level, steady vessel, and UK maritime guidance instructs crews to suspend lifting operations when the weather deteriorates.
What is a deck crane?
A deck crane is a crane fixed to the deck of a ship or boat to lift cargo, stores and equipment on board, ashore or onto another vessel. On large cargo ships it is often a heavy electro-hydraulic cargo crane. On small and mid-size vessels, it is usually a hydraulic knuckle boom or telescopic boom crane on a steel pedestal. People also call it a marine deck crane, ship deck crane or boat deck crane.
The name causes some confusion in search results. A carry deck crane is a different machine: a small wheeled mobile crane that travels around industrial plants and yards carrying loads on its own deck, and it is not installed on ships. The table below sets out the main differences.
| Type | Where it works | What it lifts |
|---|---|---|
| Hydraulic deck crane | Fixed on a pedestal on a cargo vessel, landing craft, workboat or barge | Cargo, stores, tools and small boats, from a few hundred kilograms to several tonnes at outreach |
| Ship’s cargo crane | Fixed on a bulk carrier or general cargo ship | Grabs and cargo slings, often 25 t and more |
| Offshore crane | Fixed on a platform or offshore vessel, built to offshore crane rules | Loads to and from supply vessels in open sea |
| Carry deck crane | On land, in plants and yards; drives on wheels | Loads carried on its own deck; not a Marine Crane |
We build the first kind: hydraulic marine cranes from 0.8 t to 25 t rated capacity. We do not build ship’s cargo cranes, offshore cranes or carry deck cranes. If your vessel is an unpowered barge or pontoon, our barge crane guide covers heel and stand-alone power.
Knuckle boom or telescopic deck crane?
Both types work well on deck, but they suit different vessels, so compare them against your deck plan and your typical loads before looking at brochures.
- Knuckle boom deck crane. The boom folds at a joint and stows in a small space beside the pedestal. It can reach over a bulwark and then down into a hold or onto a low quay. It usually lifts more at the end of its reach. Our 10 t knuckle boom lifts 1,150 kg at 14.68 m.
- Telescopic deck crane. The boom extends in a straight line. It reaches further for its weight class, which suits long lifts from deck to quay. It stows along the deck on a boom rest, so plan that space. Our 20 t telescopic lifts 1,500 kg at 22.0 m.
A general rule from our installations: choose a knuckle boom when deck space is short or loads go below deck. Choose a telescopic boom when the vessel has a long open deck and the lifts are to and from the quay. Our marine crane buying guide compares the two boom types across the full range.
How much outreach does your deck crane need?
Outreach is the horizontal distance from the crane’s slewing centre to the hook. Measure it on the deck plan, not on the crane brochure. Mark the pedestal position, then measure to each place you lift from or land on. That is usually the far side of the cargo deck, the hatch, the quay when you lie alongside, or a boat moored outboard.
Then add the transverse distances. A crane installed on the centreline of an 8 m wide vessel already needs 4 m of outreach to reach the rail, and landing a pallet 3 m back from the quay edge takes the requirement past 7 m before any gap between hull and quay is included. A crane mounted at the side reaches the quay more easily, but it must cover the full beam to serve the opposite side of the deck.
The chart shows why rated capacity is a misleading guide on a ship: our 8 t telescopic crane reaches 18.5 m but lifts only 400 kg there, while our 8 t knuckle boom reaches 14.68 m and still lifts 850 kg at that distance. If your heaviest load is a 1 t pallet at 14 m, the 10 t knuckle boom (1,150 kg at 14.68 m) covers it and the 8 t models do not. Read the load chart at your real outreach, with a margin for slings, nets and the hook block. Our guide on how to read a crane load chart walks through the method.
Deck space and stowage at sea
A deck crane spends most of its working life stowed. While the vessel is under way, the boom must rest in a secure position with the hook fastened, so that it cannot swing when the vessel rolls in a seaway. Plan the stowed footprint on the deck plan as carefully as the working outreach.
The photo shows a typical layout on a small cargo vessel: the crane stands at the forward end of the cargo deck, immediately behind the wheelhouse. When stowed, the boom stays clear of the cargo area, so the entire deck aft of the crane is available for pipes. A knuckle boom folds into an even smaller envelope, which is particularly useful on short decks. Its stowed width and height are on its dimension drawing; check them against the wheelhouse view and the navigation lights.
Crane weight, deck strength and stability
A deck crane adds weight high above the deck and transfers a considerable overturning moment into the hull structure whenever it lifts. On our drawings, crane weight ranges from 220 kg for the 0.8 t model to 6,950 kg for the 20 t telescopic, and maximum lifting moment ranges from 1.3 t·m to 53 t·m. The deck beneath the pedestal therefore needs local reinforcement, and the vessel’s stability must be verified with the crane installed and operating.
UK maritime guidance puts it plainly. Under MGN 332, the guidance to the ships’ lifting equipment regulations, a suitably qualified person should check the vessel’s stability before a crane is installed [1]. It calls this especially important on workboats and other small vessels, and recommends asking the crane manufacturer for advice. We supply the crane weight, its foundation loads and the load moments for that check.
Our Egypt customers show a typical small-vessel set-up. Their SQ5ZA3T knuckle boom deck cranes on harbour workboats sit on raised pedestals, with a seated control station, an access ladder and a hydraulic power unit on deck. The pedestal lifts the boom clear of the rails and deck gear.
Lifting at sea: what the load chart does not cover
A load chart assumes a steady, level base. On a vessel, roll, pitch and heel swing the suspended load and add dynamic force to the boom, and wash from passing ships has the same effect in harbour. The rated loads therefore hold only when the vessel is moored, level and steady.
The UK regulations require lifting to stop when the weather deteriorates [2]. MGN 332 adds that lifting should stop before conditions become dangerous. It also warns that overloading a crane on a small vessel can, in some cases, sink it [1]. Under the same regulations, lifting equipment on UK ships needs a thorough examination at least every 12 months, or every 6 months if it lifts people. Other flag states set their own rules, so check yours.
How to power a deck crane
Every crane in our range runs on hydraulic oil at a specified flow and pressure, and a self-propelled vessel offers two common ways to supply it. A pump on a power take-off from the main or auxiliary engine is simple, but the crane only works while that engine is running. An electric hydraulic power unit on deck draws on the ship’s electrical supply, so the crane can operate in port with the main engine stopped.
Size the pump from the specification on the drawing. Our marine cranes require from 3.5 kW and 8 L/min (0.8 t) up to 55 kW and 80 L/min (16 t telescopic), with operating pressures between 16 MPa and 35 MPa; the 20 t telescopic uses two hydraulic circuits, 80 + 63 L/min. Give these figures to the shipyard or electrical contractor who specifies the power unit.
Deck crane sizes by vessel and job
The table groups our current marine cranes by the jobs we see them do. Figures come from each model’s technical drawing; the load at full outreach is the last point on its load chart.
| Typical use | Model (rated) | Boom | Load at full outreach | Crane weight | Hydraulic supply |
|---|---|---|---|---|---|
| Stores and small boats on yachts and small workboats | SQ08ZA3TJ+1 (0.8 t) | Knuckle | 220 kg at 4.151 m | 220 kg | 8 L/min, 18 MPa |
| SQ2ZA2TJ (2 t) | Knuckle | 750 kg at 5.1 m | 590 kg | 20 L/min, 20 MPa | |
| Cargo on workboats and small cargo vessels | SQ4ZA3TJ (4 t) | Knuckle | 850 kg at 7.7 m | 1,256 kg | 25 L/min, 26 MPa |
| SQ5ZA3TJ (5 t) | Knuckle | 1,100 kg at 8.05 m | 2,120 kg | 35 L/min, 28 MPa | |
| SQ6.3ZA4TJ (6.3 t) | Knuckle | 1,190 kg at 10.2 m | 1,740 kg | 40 L/min, 28 MPa | |
| SQ6.3SA4T (6.3 t) | Telescopic | 600 kg at 12.6 m | 2,200 kg | 40 L/min, 20 MPa | |
| Cargo vessels, landing craft and supply boats | SQ10ZA6TJ (10 t) | Knuckle | 1,150 kg at 14.68 m | 2,920 kg | 40 L/min, 30 MPa |
| SQ12SA4T (12 t) | Telescopic | 1,200 kg at 16.19 m | 4,050 kg | 75 L/min, 26 MPa | |
| SQ16SA5T (16 t) | Telescopic | 1,050 kg at 22.3 m | 5,800 kg | 80 L/min, 30 MPa | |
| SQZ430T (20 t) | Knuckle | 1,910 kg at 16.6 m | 4,900 kg | 63 L/min, 33 MPa | |
| SQZ500T (25 t) | Knuckle | 2,000 kg at 18.0 m | 6,474 kg | 80 L/min, 35 MPa |
Models with J in the code, such as the SQ10ZA6TJ, are drawn with a winch drum for lifts below the crane base. Winch pull and rope length are not on the drawings, so we confirm them with the quotation. The full lists are on our knuckle boom marine crane and telescopic boom marine crane pages. For boats under 10 m, see our boat crane guide.
Deck crane on a cargo vessel: a Maldives example
Our Maldives customers operate telescopic deck cranes on open-deck cargo vessels and on a harbour quay. One of their vessels carries an earlier 16 t telescopic model, installed at the forward end of its cargo deck. In the photos it carries lashed pipes and timber, which the crane lifts between the deck and the quay. The long straight boom suits that operation particularly well: the vessel lies alongside, and the crane delivers each load across the quay in a single movement.
Corrosion protection and care
A deck crane operates in constant salt spray, so ask your supplier about the paint system, the protection of cylinder rods and pins, and how the electrical components are sealed. After delivery, keep a simple maintenance routine: rinse the crane with fresh water after work in spray, grease the slewing ring and pivots on the schedule in the operating manual, and keep the boom stowed with the hook secured whenever the vessel is moving.
Deck crane checklist: six steps
- Loads. List your heaviest load and the one you lift most frequently, including slings, nets or a lifting frame.
- Outreach. On the deck plan, measure from the slewing centre to each pick-up and landing point, over the side.
- Load at outreach. Choose a crane whose load chart covers that load at that distance, with a margin.
- Stowage. Check the folded or rested boom position against the deck layout, the wheelhouse visibility and the navigation lights.
- Deck and stability. Provide the crane weight and foundation loads to your shipyard or naval architect for verification.
- Power. Confirm a PTO pump or an electric power unit that meets the crane’s flow and pressure.
Frequently asked questions
What is the difference between a deck crane and a carry deck crane?
A deck crane is fixed to a ship’s deck and lifts cargo on and off the vessel. A carry deck crane is a small wheeled mobile crane that works on land, in plants and yards, and carries loads on its own flat deck. We build marine deck cranes, not carry deck cranes.
Can I fit a truck crane on a ship’s deck?
We do not recommend it. A truck crane is protected for road use, not salt spray, and its base is designed for a truck chassis. Our marine models, marked T in the code, share the lifting geometry of the truck versions but are built for work at sea and fit on a deck pedestal.
How big a deck crane does a small cargo vessel need?
Work from the heaviest load and the longest outreach, not from the vessel’s overall dimensions. As a rough guide from our drawings: about 1 t at 8 m needs a 5 t knuckle boom (1,100 kg at 8.05 m). About 1 t at 14 to 16 m needs a 10 t knuckle boom or a 12 t telescopic. About 1.5 t at 22 m needs the 20 t telescopic.
Can a deck crane lift while the vessel is moving?
Load charts assume a steady, level vessel, so moor the vessel and lift in sheltered water whenever possible. If roll or swell begins to swing the suspended load, stop the operation. UK rules require lifting to halt when the weather deteriorates, and other flag states have similar rules.
Do I need a winch on a deck crane?
You need one when loads go below the crane base, for example into a hold, onto a low quay or into the water. The winch pays out rope, so the hook can go lower than the boom tip. Our knuckle boom models with J in the code are drawn with a winch drum.
Get a deck crane matched to your vessel
Send us the deck plan, the vessel’s length and beam, your heaviest load and the outreach you need over the side. Tell us how you plan to power the crane. We will propose a model with its load chart, weight and foundation loads, so your yard can check the installation. Contact us for a quotation.
