Spring lines are one of the simplest ways to gain more control over a Motorboat alongside a pontoon. They limit movement forwards or astern, help keep the boat settled when wind, tide or wash is acting on it, and can also be used to help a boat leave a berth when it is being held against the pontoon.
They are most useful when everyone aboard understands what the line is meant to do. A spring in the wrong direction, or a line loaded with too much engine power, can make a straightforward manoeuvre harder rather than easier.
What does a spring line do?
A spring line runs diagonally between the boat and the pontoon. Its main purpose is to control fore-and-aft movement.
A spring leading aft from the boat prevents the boat moving forwards. A spring leading forwards from the boat prevents it moving astern.
This is often easier to remember than concentrating on the names given to individual springs. Before securing the line, ask which direction you need to prevent the boat from moving and choose the pontoon cleat accordingly.
When the boat is left alongside, springs normally work with bow and stern lines to keep it positioned within the berth.
The line should have a clear lead between suitable strong points on the boat and pontoon. Avoid running it across sharp edges or somewhere it can become trapped or badly chafed.
Spring lines and breast lines are not the same thing
Spring and breast lines control different types of movement.
A spring line runs diagonally and primarily prevents the boat moving forwards or backwards.
A breast line runs more directly between the boat and pontoon and primarily limits sideways movement away from the berth.
Alongside mooring arrangements often use both because a boat needs control in more than one direction. Bow and stern lines, springs and breast lines can each have a role depending on the berth and conditions.
Avoid pulling every line as tight as possible. The boat still needs to respond safely to changes in water level, wash and movement at the berth. This is particularly important against fixed quays where the vertical distance between the boat and the mooring point can change considerably with the tide.
Prepare spring lines before the final approach
Sort the lines and fenders before entering the berth.
Decide which line you want first and make sure the crew member handling it knows where it needs to go. A spring can provide useful control soon after arriving alongside, particularly when wind or tide is trying to move the boat along the pontoon.
Keep the crew briefing straightforward. They should know which line they are handling, which cleat it needs to reach and what to do once it is secured.
Nobody should need to jump from the boat to make a line fast. If the boat is not close enough for a safe step or for the line to be passed ashore, reposition the boat and try again.
Keep hands and feet away from the gap between the hull and pontoon, and never wrap a mooring line around a hand or arm. A line that suddenly takes the weight of a Motorboat can generate a considerable load.
Using a spring once you are alongside
The direction in which the boat wants to move determines which spring will be most useful.
If the boat is creeping forwards along the berth, use a spring that leads aft from the boat to prevent that movement. If it is moving astern, a spring leading forwards will provide the restraint.
Conditions can change after the boat has been secured. Wind direction, tidal flow and wash from passing vessels can all alter the loads on the lines.
This is particularly relevant in tidal areas such as the Solent. A berth that is settled when you arrive may behave differently several hours later.
Check the lines rather than assuming the arrangement that worked on arrival will remain suitable throughout the stay. Look at line tension, chafe points and the position of fenders as part of those checks.
How can a spring line help when leaving a berth?
A spring can be particularly useful when wind is pressing a Motorboat against the pontoon.
Simply applying power away from the berth may not give the control you expect. The boat can remain pinned against the fenders while the bow or stern begins moving in an unhelpful direction.
Instead, a spring can restrain one part of the boat while gentle propulsion encourages the other end to move away from the pontoon.
For example, a correctly positioned spring may allow the stern to move away while the forward part of the boat remains controlled. Once there is sufficient clearance, the spring can be released and the boat can move into the fairway.
The same principle can be used to create space at the bow with a different spring arrangement.
The exact response depends on the boat. Shaft drives, sterndrives and outboards can behave differently, while hull shape, propeller effects, wind and tide will also influence the result. Learn how the technique works on the Motorboat you actually use rather than assuming the same control inputs will produce the same result on every vessel.
Use as little power as necessary
A spring departure does not require large amounts of throttle.
Once the line is loaded, engine power is being transferred through the boat’s cleat, the rope and the pontoon fitting. Applying unnecessary power increases those loads and can cause the boat to pivot more quickly than expected.
Start with minimal power and watch the response.
Fenders should be positioned where the boat will bear against the pontoon during the manoeuvre. Crew handling the spring must also remain clear of the bight of the rope and anywhere they could be injured if the line suddenly tightens.
If the manoeuvre is not developing as expected, stop and reassess rather than adding more throttle.
Check where the boat will go next
Getting the bow or stern away from the pontoon is only the first part of leaving the berth.
Before loading the spring, check the space around the whole boat. Consider where the opposite end will move as the boat pivots and whether there is enough room to complete the manoeuvre.
Look at the fairway as well. Another boat entering the marina, a tender moving between pontoons or somebody manoeuvring from the berth opposite can remove the space you expected to use.
Wind and tide may also start affecting the boat differently as soon as it moves clear of the shelter provided by the pontoon and neighbouring vessels.
If conditions are already taking the boat away from the berth, there may be no reason to use a spring at all. Use the simplest manoeuvre that gives you control.
Common spring line mistakes
A few problems account for many difficult spring-line manoeuvres.
Leading the line in the wrong direction means it will not prevent the movement you intended to control.
Using too much power places unnecessary load on the rope and fittings and can make the boat move more quickly than expected.
Poor fender positioning can leave part of the hull unprotected as the boat pivots against the pontoon.
Releasing the spring too early can allow wind or tide to take control before the boat has reached a useful angle.
Leaving the spring too late creates the opposite problem. The boat may already be trying to move away while the line is still holding it back.
Clear communication between helm and crew matters throughout. The person handling the line should know when it needs to remain secured, when it can run and when it should be released.
Practise springing off before you need it
A quiet pontoon and light conditions are far better places to learn spring lines than a crowded marina with a strong crosswind.
Start alongside and see what happens when a spring takes the load. Use very small engine inputs and watch which part of the boat remains restrained and which part moves. Repeat the exercise with different spring arrangements.
It is a useful extension of close-quarters boat handling, because it teaches you to use lines, propulsion and the conditions together rather than relying on engine power alone.
Once you understand how your own Motorboat responds, spring lines become much easier to use. They give you another way to control movement alongside and can turn an awkward departure into a slower, more predictable manoeuvre.
FAQs about spring lines on a Motorboat
How long should a spring line be?
A spring line needs enough length to run diagonally between suitable strong points on the boat and shore while still allowing the crew to handle and adjust it safely. The useful length therefore depends on the size of the boat and the type of berth rather than one standard measurement.
Can you use a midships cleat for a spring line?
Yes, where the cleat and arrangement are suitable for the load. Midships cleats can provide useful options when rigging springs, particularly during short-handed berthing, but lines should always be led through fittings designed to take the expected load.
What type of rope is suitable for spring lines?
Mooring rope should be suitable for the size and weight of the boat, comfortable to handle and in good condition. Some elasticity can help absorb movement and shock loads, but the correct rope type and diameter should reflect the vessel and mooring arrangement.
Should spring lines be left rigged while a Motorboat is unattended?
Springs commonly form part of the normal mooring arrangement when a boat is left alongside. The complete set of lines should suit the berth, expected tide and conditions, with enough allowance for movement and changes in water level where necessary.
Can spring lines be used against both floating pontoons and fixed quays?
Yes, but the mooring arrangement needs to suit the location. A floating pontoon rises and falls with the boat, whereas the vertical relationship between a boat and a fixed quay changes with the tide. This can affect line length, lead and how much movement needs to be allowed.