Boats and outboard motors selected by MSF are intended for emergency situations: as lightweight as possible, and simple to assemble and operate.

If you use water transport regularly in your mission, the appropriate choice of boat and engine is more complicated.

Ask your technical department for advice.

BUY OR RENT

The choice between purchase or rental is usually based on 3 criteria: availability, quality and price.

Availability

Compare the lead time to the requirement.

Quality

The technical standards used by those who sell or hire boats are not reliable measures of quality.

In case of rental, check that the boat is in good condition (engine, safety devices, fuel quality etc.) and that there is no repair required that could subsequently be attributed to lack of maintenance by MSF. Think about establishing a system of quality checks and carry out regular assessments (once a year).

In case of purchase, try to follow the general specifications given below.

In either case, ask your technical department for advice, and if possible ask other organizations about their experiences.

Cost

In case of rental, the decisive point is not the price, but the quality! Choose a company that offers good quality over one that offers the lowest price.

In case of purchase, costs are important, especially the initial investment. Make a proposal to the financial coordinator. The higher the initial investment, the longer it will take to recover the cost.

EFFICIENCY

Water transport by slow vessel is the most energy-efficient. "Slow" corresponds to the hull's displacement speed (also known as "hull speed"), expressed as follows:

S = 4.5 x the square root of L

S = displacement speed in km/h

L = waterline length of the boat in m

If a higher speed is required, the fuel consumption will increase drastically. At a certain point, the bottom of the boat – if it is designed for this purpose – will rise to the surface of the water as a result of its speed: this is known as planing. Once the boat is planing, the fuel consumption will drop, but it will stay far above the consumption of a slow vessel.

Planing starts at about 25 km/h, depending on hull design and total weight.

For each boat design, the manufacturer or supplier produces a graph showing estimated speeds and a curve plotting weight against required engine horsepower. These graphs also indicate the planing speeds.

CHOICE OF BOAT

Before choosing a boat, it is essential to assess the requirements and conditions of use.

The type of propulsion, the shape, the size and the weight of the boat will be determined by:

• the environment: river with clear or turbid water, or with floating or submerged objects (tree trunks etc.); fresh or brackish water, or coastal salt water; shallow or deep water etc.
• the required payload
• the required speed
• the required range
• the engine selected (see "choice of engine" below)

A long wooden canoe (± 15 metre) equipped with a small 25 HP outboard motor is a good example. It has good energy efficiency, good payload and reasonably good speed (close to 20 km/h).

Such a canoe can easily carry 500 kg of cargo, 200 litre of fuel and 8 people for about US $0.20/km.

STANDARDIZATION AND LOCAL MARKET

Choice of engine

Most MSF boats have outboard engines.

Two-stroke outboard engines have the advantage of being simple, lightweight, reliable and efficient. They are also easy to maintain and can be repaired almost everywhere. However, it is likely that two-stroke engines will gradually disappear from the market and be replaced by four-stroke engines. Two strokes engines are more and more difficult to find, report to your supply center for availability.

Four-stroke outboards are less noisy and have a greater range and longer lifespan. They are more demanding to maintain, slightly heavier and more expensive, but they are the most economic engines in the short and medium term.

Four-stroke outboards are therefore preferable if they are available locally. However, you should be aware that introducing them often leads to difficulties and negative feedback from local people and boat drivers, hence the importance of proper training.

If you opt for an inboard engine, choose a diesel model rather than a petrol one. Inboards are the most economic engines in the long term.

Choice of propeller

Due to the wide variety of types and sizes available, it is very important to make the correct choice. There is a wide variety of types and sizes available. The standard propeller delivered with any outboard engine is a three blade aluminium propeller with a pitch intended to be used on a fast (light) boat. Aluminium propellers are cheaper compared to stainless steel ones that last longer. If you want to use the outboard engine on a slow boat, ask for advice from the supplier or your support department. An incorrect match of propeller, engine and boat will result in high costs and reduced lifespan.

"Water jet" propulsion is another option; it should be limited to inboard engines and to boats operating in shallow water. Water jet propulsion provides better manoeuvrability, but is less efficient.

Choice of hull

For slow boats, the weight is not very important. Hulls are often made of wood or steel.

For fast boats, weight is an important factor in fuel consumption and costs. Ranked according to increasing weight, the options for fast boats are:

• welded aluminium
• glass reinforced plastic (GRP)
• welded steel

Provided that the boat is suitable for the context and that all materials meet our requirements, the choice will be determined by the local availability of repair facilities.

When you buy a boat

Enquire about the local boatyard's quality and reliability. Test a boat which is equivalent to the one you intend to buy, with the same engine and same power.

Order the boat with an engine, sold and fitted by the boatyard. If this is not possible, or if you decide to order the engine from a different supplier, follow the boatyard's recommendations and make it responsible for the final functioning of the boat/engine combination.

Do not forget to specify the propeller you have chosen in the order or quotation request, and to include a fuel tank, buoyancy chambers etc.