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Boat Handling - Small Boats

Trailing|Launching| Loading | The Coxswain | Handling Inflatables |Anchoring|Outboard Engines
Boat Trim
|Weather| Fuel Usage | Planing | Handling in Rough Seas | Remote Areas | Equipment

Trailing Boats

Most boats are transported to the sea aboard boat trailers. These should be robust and have heavy-duty wheels and suspension if they are to be used on anything other than short journeys along good roads.
You must comply with law relating to trailing regarding loadings, lights, sharp projections and speeds. Load the trailer so that it is about 25 kg nose-heavy; secure items transported inside the boat. It is best not to use the boat as a baggage trailer. Cover the propeller with something substantial, such as a heavy plastic bucket.

Launching Boats

Launching a boat should be carried out with intelligence and prior planning. The exact technique will depend on the size and weight of the craft and on the shoreline features. These can vary from manhandling the boat over very broken ground to launching from a smooth slipway.
Most diving boats are now launched from trailers, and a simple, methodical procedure should be employed.
1. Ensure the boat is ready for the sea / water. Fully inflate inflatable tubes. Check fuel, and fuel control lines, anchor and other boat equipment, safety and emergency equipment.
2. Untie the boat from the trailer.
3. Wheel the trailer into the sea until the vessels floats off.
4. Two people should hold the bow into any waves to avoid broaching.
5. Pull the trailer out and take above the high waterline and stow it sensibly.
6. The rest of the party should load equipment under the supervision of the coxswain.
7. The coxswain places gear where required.
8. The coxswain starts the engine, the diving party gets aboard and the diving trip commences.

Loading Boats

To put large amounts of diving equipment in an inflatable obviously requires a certain amount of organization. The toolbox and emergency box go under the spray deck along with a basket for the anchor system and other odds and ends. All should be stowed so that is available in an emergency. It is useful for each of the four divers to be given a 25 liter, square plastic container with cutaway sides for equipment; these are lashed across the boat immediately aft of the spray deck. Next come the scuba units (unless the protocol is for them to be donned beforehand), followed by weightbelts. Finally the divers themselves, two fuel tanks, plus a container for cameras and sensitive equipment. This layout of divers and equipment works well, especially on longer boat journeys.
The boats manufacterers specifies the maximum load that a small craft is designated to carry.
The maximum is for still water conditions. In sea conditions, the max load should be reduced, and in heavier conditions the loading will have to be substantially reduced.

The Coxswain

The coxswain - which is olde English for boat pilot, is in total command of the craft and is responsible at all times for its safety and the safety of the passengers. He must be a good seaman with appropriate experience of small boat handling. Things to be aware of include: Boat conditions, events in the craft, engine and gear settings, weather and sea state.

Handling Inflatables

Most inflatables for diving are capable of reaching planing speeds when adequately powered. There handling characteristics are different to other types of boat and should be learned thoroughly before taking out divers diving. The final approach to the dive site will be done in neutral gear so low speed handling must be understood.
Small boats powered by outboard engines are usually steered by a tiller (also controlling acceleration) moving the propeller thrust in the direction that you want the boat to turn. This gives great manouverability at low speeds with low engine throttle positions.
At high speeds, small boats will bounce badly in even quite small waves. There is a risk of bouncing both people and equipment out of the boat. Speed must be reduced to counter this, although for economy and time it is best to plane whenever possible. The best tactic is to use all the engine power to get the boat onto the plane and then to reduce the throttle position until the boat is at the minumum planing speed, this will be the most comfortable for the passengers and most economical on fuel.
When planing, the boat is skimming over the water and sharp turns are not possible. The boat slides sideways in turns. The amount of slip being governed by the 'V' in the boats hull.
In an emergency it is not enough to merely cut the throttle and put the boat into neutral, the boat will not stop rapidly as the stern wave and the forward momentum will carry the boat some distance onward. A crash stop will can be achieved by simultaneously pushing the tilller fully in one direction. This causes the boat to go sideways and the stop in a few feet. Another essential manouver to know is the man-overboard drill. The Anderson and Williamson Turn are some of the few effective ways of heading the boat out and around and back to recover a man overboard, the former in good visibility and the later in poor visibility. Sharp reactions, a compass, judgement and spatial awareness are key to pulling off an accurate manouver on-the-fly, which results in a reciprocal heading.
It is most important to learn and practise all aspects of small boat-handling. A boat-handling course is the most effective way of achieving this.

Anchoring Boats

There is much to be said for not anchoring a diving support craft if it operating singly and much to be said for anchoring the main support craft if there are two or more boats. Generally it is best practice to have one vessel covering the divers quite closely. An anchor system is an essential bit of kit, without it vessel will be relying on mooring buoys at dive sites (useful but they aren't always there) or wasting fuel remaining to remain on station.
Anchor line should consist of chain (10 M) and then a 10-12mm rope (natural or synthetic) of between 30 - 40 M running up to and into a bucket were it is stowed. It is handy to punch a small hole in the bottom and pass the remained of the rope through and secure it onto a buoy. This way the whole anchor system can be jettisoned in emergency, then recovered later. Pay out a length two or three times the depth you are at to aid easing the strain on the anchor line, more if conditions are rough. When the anchor has rested make a loop in the line and carabiner the loop and then snap the carabiner it onto a suitable anchor point on the prow of the boat. The remainder of the line can be stowed on board in its bucket. If you're planning on diving deeper than the anchor system you have rigged up then add on extra sections of rope connected by snaplinks or double-sheet bends.
Weighing (lifting) anchor is best done by motoring slowly forward as a diver / crewman takes in the slack anchor rope, when the line is vertically over the anchor it should lift off the bottom. If not then its possible to 'motor' it out, depending on the anchor type and the seabed composition. If this fails then either a pair of divers with low nitrogen counts can attempt to retrieve it manually or simply abandon it altogether. Another altogether different anchor is the sea anchor: usually a fabric drogue that can be used as a brake in an emergency and also can bring a vessels bows into the waves if the even of engine failure. Life rafts also use them to reduce drift in an emergency.

Outboard Engines

An outboard engine powers most small diving boats, these are very powerful for their physical size and they are quite reliable when correctly maintained.
A small inflatable carrying four kitted divers requires at least a 25 h.p engine to plane, otherwise a motor that is smaller will only be adequate for displacement speeds. A boat planes across the water will move faster than a boat which displaces water as it sits higher in the water and rides across it. Another factor influencing this will be the shape of the hull, a planing (high speed)hull will, due to the shape of its hull plane across the water naturally. The propeller sits quite low under the boat and inclined slightly from the horizontal enchancing its effect, however care must be taken in any treacherous shallows not to damage or destroy the propeller and rudder. A planing hull is inherently more unstable than its counterpart, the displacement hull but can cover vast distances on a frugal amount of fuel and it is faster.
A displacement hull sits lower in the water and is more stable, it has to 'push' through the water and even at high speed it will not plane, which is opposed to the gliding effect a planing hull has on the water. The propeller and rudder sit higher than a planing hull and can navigate in the shallows more easily. Some hull types may combine qualities of both the displacement and planing hull. The Asian longtail type of hull being a hybrid example.
For larger craft carrying more divers and equipment over longer distances in bigger seas, the engine must be imcreased in size to between 40 h.p and as much as 125 h.p. Too much power can be wasted on a small boat and can even be dangerous, particularly in realtively inexperienced hands.
Engine layouts vary somewhat, but starting is usually by a pullcord at the top of the engine. Most engines are fitted with a manually controlled choke for starting. All but the smallest outboard engines require a separate fuel supply from a remote tank via a flexible hose. Throttle control and steering is provided by the tiller arm, while the gears are usually controlled by a separate lever on the side of the engine. An emergency-stop button is essential, although, although its position depends on the make of engine.
Larger engines are normally bolted permanently to the transom of the boat. They are usually fitted with remote throttle control, steering, electric starting and sometimes engine tilting.

Outboard Engine Fuel Supply

Outboard motors are usually two-stroke engines running on a fuel of petrol with two-stroke oil mixed in a ratio of anything between 1:10 and 1:100. You must use the correct mix for your engine.
Some high-powered outboards use a separate oil tank and inject oil to vary the oil-fuel ratio according to the engine loading.
Some fuel tank filler caps have an air bleed valve incorporated to allow air to enter the tank to replace the fuel as it is used. Do not forget to open it when running the engine!
Fuel tanks can be located out of the way under the bows. The fuel line is vulnerable to sharp edges or heavy weights, which can respectively cut the line or restrict the fuel flow. Both of these events usually stop the engine. A spare fuel line is a wise (if unusual) precaution.

Boat Trim

A well trimmed boat can mean the difference between the boat making good speed and economy while looking impressive to the complete opposite. Boat trim is controlled by two factors - The engine tilt angle and the weight distribution in the boat.
For a boat to plane correctly the tilt angle must be just right. This is normally adjusted by moving a large pin behind the engine's transom mount from one set of holes to another. If the tilt angle is to great, the boat's bow will points upwards and the stern digs in. If the tilt angle is too small then the bow digs in and the stern tends to rise.
If the entire load in the boat is near the stern then the stern will tend to dig in. Conversely, all the weight in the bows will cause the stern to rise. In extreme cases, this can allow the propeller to draw air down and cavitate. This is manifested by engine racing and loss of power.
The weight in a boat is best distributed fairly evenly, with perhaps a slight bias towards the stern. This varies from boat to boat, so some trial and error is required. Indeed, with a boat that is somewhat underpowered, it may be necessary to move some weight forward to enable it to plane initially.


Before diving it is obviously important to listen to the weather and shipping forecasts and carefully evaluate them. When following the weather it is useful to have a small pocket barometer. Take the advice of fishermen and other locals, although a group of experienced divers in a well-kitted inflatable is a substantially more seaworthy combination that some of the small boats used by inshore fishermen.
Even in moderate weather it is recommended that it is wise to exercise much caution. Turning back or not starting out when conditions are doubtful do not require the judgement born of years of experience.

Fuel Usage

Boating distances can sometimes substantial; thus you must plan your fuel accordingly. If you work on the formula of half a liter of fuel per horsepower per hour, you will only slightly overestimate the fuel consumption of modern outboards on full throttle. It is also useful to know how long your outboard will run on full throttle on a full tank of fuel as this gives an idea of operating range. It is imperative to rememer that sea conditions may allow you to plane to a site, but may prevent you from doing so on the return tip. Running off-the-plane as a displacement craft will use at least four times as much fuel as on-the-plane for the same distance. Faulty plugs and badly adjusted outboards also use more fuel.


There are very many sites in British waters that can only be realistically reached by a planing vessel. Such a craft will also sometimes allow you to beat bad weather home. Ensure that your boat, when fully loaded, has a reserve of power to enable you to plane whenever sea conditions allow. This increases the safety of the excursion generally and also allows the divers to spend less time on boat journeys, which are therefore, less chilling and not so tiring.

Handling in Rough Seas

The preparation of both boats and personnel must be more thorough when you intend to operate in heavier seas. The equipment used should be of heavier duty and must be fully comprehensive. The crew will have to be more experienced to be effective.
When planing into strong winds there is a significant chance that a lightly loaded inflatable will be flipped right over. There should always be more than one person aboard and the extra people should sit well forward as ballast.
When travelling slowly with a following sea there is always a chance of pooping i.e. having a wave catch up the boat and swamping it over the transom. Thus a robust boat should not have a low, cut-out transom to accommodate the outboard engine. Either use a false transom or a long-shaft motor. The direction and strength of the wind and how long it has been blowing largely determine what can reasonably be tackled in a small boat. It is not possible to quote categorically what is or is not feasible - so much depends upon the boatman and crew, the type of craft and what shelter there is from islands and headllands. As a general indication, a wind of Force 4 or 5 will usually make life uncomfortable in a small boat, especially if the coast is very exposed and the wind has been blowing for some time. Furthermore, the effects of wind and tide working against each other should never be underestimated. Conversely, an offshore wind gives apparently excellent and enticing sea conditions, but beware an engine failure.
When caught in difficult sea conditions, it is often possible to take a longer, but safer route back, using the shelter of islands, headlands or planing along the wave troughs to avoid a more time and fuel-consuming displacement journey. In many conditions you will find the need for a second 25 liter tank of fuel, occasionally more. Having the extra fuel in an outboard tank, although expensive, is far superior to petrol-can-funnel transfers.

Boat Diving in Remote Areas

At exposed sites the use of two boats operating together is sound sense. For the bast bulk of dives the second boat is a good insurance against breakdowns in remote areas. In the bigger seas experienced on exposed coasts it is prudent to plan for a slightly smaller load than normal. Reducing the load too far obviously brings the danger of lifting in the wind, whereas too great a load causes continual shipping of water in some seas. For a 4-5 meter inflatable a maximum of four divers with equipment is prudent, whereas in more sheltered waters it might be possible to have six divers in such a craft. Two inflatables of such a size, each with three divers and a boathandler, are a very vesatile combination. At many sites, this allows one boat to be anchored, while the other acts as a pick-up and cover craft. A portable VHF radiotransmitter should always be carried.
When operating well away from normal bases it is advisable to take many more spare parts, along with the tools and knowledge to use them. The boats and engines should be in tip-top condition before being taken to remote areas. The backup required is greater and should certainly include two-way radios. It is most desirable to operate vessels in groups of at least two.

Boating Equipment

The equipment you carry in you boat should (ideally) be beyond reproach, as you should give yourself every chance of a successful trip.
This list of boat equipment is so complete that it would impress Ulysses! No equipment or spare part is ignored allowing emergency repairs and replacement of parts in emergency. For more modest expeditions and where space / weight limits restrict (on smaller boats for example) feel free to cut down on some of the items :

In Boat:

4 Paddles, Pump, Baler, bilge pump, 5kg CQR on 3m chain, 5 kg folding anchor (backup), anchor warp (150 meters on 10mm rope), sea anchor, additional rope, 3 buoys, rigid pole with diver flag, charts (photocopy sealed in clear sleeve), decompression table, hot drink, spare fuel tank (25 liters), further spare tank, spare emergency engine (small 4 h.p).

In Tool Box:

Spares: plugs, shear pins, split pins, propeller nut, propeller, starter cord, fuel line, bolts etc.
Repair materials: plugs for hull, hull patches, glue / emery paper, insulating tape, heavy copper wire, WD40, etc.

In a Sealed Emergency Box:

Flares - 4 parachute, 4 hand, 4 smoke. 4 diver recall signals (weighted), whistle, torch, compass, emergency food (glucose tablets, chocolate, raisins, toffee bars), water, self-heat soup, space blankets, first-aid kit (including sea sickness tablets), coinage, large-denomination note for fuel purchase.

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