Motorboat Expert

Independent Yachting Magazine

The main principles of fuel economy

Fuel economy on yachts and motorboats

Updated on June 9th, 2024

Fuel will continue to rise in price until electric motors can create enough competition for internal combustion engines, so saving fuel is becoming an increasingly important issue for owners of boats and motor yachts. In addition, reducing its consumption to some extent will help reduce harmful emissions.

Some points can be difficult, but if you do them all, you can reduce the consumption of gasoline or diesel fuel by 10-12%, which in the long run can provide significant budget savings.

1. Air streamlining of the hull

Any objects protruding beyond the line of the side, glazing or superstructure create harmful air resistance. The most common example is the soft canopy over the cockpit. If it is not necessary, then when moving it is better to fold it or remove it completely. Otherwise, at cruising speeds, it plays the role of a good parachute.

2. Angle of attack of the boat hull

Each boat hull has its own optimal mode of movement, which includes the angle of attack to the surface of the water. The high rise of the bow, as well as its excessive lowering, not only increases fuel consumption, but also negatively affects seaworthiness, handling and safety. On planing boats, the initial incorrect fit of the hull complicates the exit to the working mode of planing.

For proper balancing, a drive trim can be used to change the angle of attack of the propeller. If this does not completely eliminate the problem, then it is necessary to redistribute the weight in the boat. Very often the bow rises too much, so moving the load from the stern to the front of the boat corrects the situation and accelerates the exit to the planing mode.

The more modest the size of the boat, the more urgent this problem. With increasing length and displacement, it becomes less significant, especially when direct drive power plants are used, rather than sterndrives or outboard motors.

3. Leave excess weight on the shore

It is logical that reducing the weight of the yacht has a great effect on fuel economy. This is by no means about cutting back on drinking water or food supplies on board, however, it is sometimes useful to audit and give someone those things that you have not used for a couple of seasons.

4. Clean hull

This is one of the most important factors. Regular cleaning of the underwater part of the boat is a must. Sometimes cleaning the hull below the waterline allows you to increase the speed by a couple of knots or more at the same engine speed.

5. Engine condition

At least once a year, you need to check the marine engine, conducting a deep inspection of the motor with the replacement of consumable components and worn parts. If your own skills do not yet allow you to do this, then even a hired specialist will cost much less against the background of possible costs for unplanned repairs due to lack of maintenance.

In addition, of course, a serviceable engine with good compression consumes noticeably less fuel than a worn mechanism. And in general, the sea is not a highway, where an engine breakdown is fraught with only temporary inconvenience. A failed propulsion system on a yacht poses a potential serious hazard to passengers and crew if it occurs on open water.

6. Slow down!

This is the easiest way to save not only fuel, but also battery charge when it comes to electric motors. For all motorized vessels there is a cruising regime in which the compromise between consumption and speed is considered optimal.

However, lovers of speed to the limit spin the engines. At the same time, the motors are at the limit of their capacities for a long time, and wear increases almost several times, but the speed increases by no more than two or three knots.

In most cases, from the point of view of economy, the most profitable is a leisurely movement in a displacement mode. Another thing is that it is not entirely advisable to buy a gliding motor yacht or a speedboat for this, and then it is better to consider trawler-type vessels or displacement gentleman’s cruisers.

7. Propeller

The propeller must be in perfect condition, since it is he who is the main link between the motor and the aquatic environment, converting the rotational movement of the shaft into the translational movement of the boat.

The propeller must be absolutely clean, and its edges must not have any damage and dents from impacts and cavitation. Even small potholes offer tremendous resistance, given the speed of rotation of the blades in the water. In importance, this item is comparable to the clean hull of the boat.

In addition to the technical condition, the propeller has such important parameters as pitch, diameter, blade area, blade thickness, emphasis and material of manufacture. Boats and yachts come with an optimally sized propeller for maximum speed, but by playing with these parameters, you can achieve excellent fuel economy by installing a propeller that is matched to individual requirements for speed, mode of movement and loading of the vessel.

However, the selection of a propeller requires at least basic knowledge and understanding of hydrodynamics, otherwise you can not only exceed the current fuel consumption, but also harm the engine by loading it too much, or, conversely, allowing it to spin up to maximum. This is true for engines of small boats that are not protected by an on-board computer. In any case, the help of professionals is often the best solution.

8. Electric boats and yachts

This is one of the best fuel economy options, if not considering sails as an alternative. Today, the cost of yachts with an electric motor powered by solar cells is very high, but there is a tendency to reduce it. The issue of the safe disposal of spent batteries has not yet been fully resolved, but I want to believe that soon we will be able to significantly improve the environmental situation on the planet and at the same time not worry about fuel consumption.