To sail elegantly with a well-tuned boat over the surface of the water, leaving only a long white foam strip in the wake, is perhaps the greatest pleasure for those who have committed themselves to motorboating. If the boat has a well-balanced and clean hull and the rudder has a little feel for the throttle, this pleasure can be even more efficient. Well, a bit at least. Of course, physics can not be ignored. The fact is that it takes quite a lot of power and fuel to lift a boat so far out of the water, to put it into a fast glide. In an era in which ships and costs are getting bigger, but in which there is also far more environmental consciousness, than even 10 or 20 years ago, every skipper can do something by himself.
The most important tips for fuel savings in short form:
- A clean underwater boat
- The right trim
- A sensitive hand on the throttle lever
- A propeller adapted to the engine and the boat
And here is the extended list of our advice on the more economical operation of your boat:
- If you do not travel long distances, avoid dragging a full tank. This is unnecessary weight, which even on smaller boats quickly makes as many extra pounds of three or four adult men on board.
- Pay attention to the weight distribution, so that your boat floats on the water line and then runs smoothly on level Kie without plowing, stamping or killing.
- View the fuel flow and calculate the speed at which you can travel most sparingly, most miles per liter.
- Get involved with conscious intention to forego full gas acceleration or be on the road with more than 80 percent of gas, because both radically screw up the fuel consumption while simultaneously pushing the range.
- The fuel consumption also passes through the ceiling as soon as the underwater vessel carries a beard, i.e., algae, mussels or other vegetation, which drastically increases the friction resistance. Therefore, keep the hull clean and, if possible, store it on land on a trailer or in a Drystack camp.
- Make assured that your boat is equipped with a propeller that is tuned to the engine.
- Speaking of Prop: A damaged screw increases fuel consumption and lowers performance or comfort. Regularly inspect the propeller and have it serviced or repaired by a propeller specialist, e.g., by using a new one. Costs little help a lot.
- Be proactive in trimming your boat, either by timely adjustment of the trim tabs or weight shifting so that they are balanced on the road, which means that the hull is sprayed at the optimum angle by the water.
- Do not forget to have regular engine maintenance.
- Avoid constant adjustment of the throttle lever, except for the sea movement.
Fuel efficiency through design
If you have not purchased a boat yet or are thinking of a new one, it is worthwhile choosing one with an efficient design. While many are longing for a sports machine with a deep V-hull that cuts through the waves, the flattering multi-purpose hull is often the better choice for a leisure boat. Low weight and a cleanly shaped hull allow a faster drainage of the water, but there are also other shapes, such as catamaran hulls, ventilated step hulls and wings that minimize the friction resistance.
However, the combination of engine and propeller and its behavior with the boat is just as important. Make sure that your engine has the appropriate weight and power for the boat tail. Especially in the case of exterior brackets, perhaps the conversion to a more modern and efficient model is worthwhile. Also make sure that you have installed a suitable propeller, that is, one that fits the machine and which can be used to reach the speeds indicated by the engine manufacturer. A wrong or damaged propeller can adversely affect acceleration as well as top speed negatively through panties if it should nevertheless grip and pull. In fact, it is often worthwhile to try out different types of propellers because the differences can be quite amazing.
Dirt on the trunk
As we have seen, fouling by weeds and barnacles affects the performance of a boat like hardly any other factor. How does the beard on the underwater boat come about? The beginning is a basic layer of microorganisms and bacteria, which multiply rapidly to develop a thin film of “slime.” Afterwards, algae are found, where weeds are formed, a very attractive food source for larvae, which subsequently lead to sea pox attack. When a so-grown boat starts off, the friction between the hull and the water is radically increased. According to the International Maritime Organization, regular cleaning can increase the efficiency of a commercial ship hull by up to 12 percent,
I have already found test boats, which cut by 30 percent, both at the top speed and the maximum efficient cruise because the hull was polluted. A 22-foot, for example, did not even get into the glide, so the resistance to friction was due to the aquaculture which had settled on the entire underwater vessel. And this was by no means a single case. Many journeys will notice the drop in efficiency over the course of the season, either by higher fuel consumption or lower top speed. Depending on the boat type, this loss can account for 15 to 50 percent of the normal power. Honestly: Is not that a proper burden of the Brieftasche, apart from the increased pollutant output, not to mention the fun of losing?
How to keep the hull clean
If you have your boat in the water, the antifouling paint is still the simplest and most cost-effective solution. Luckily, there have been many effective and eco-friendly products as an alternative to the chemical control of recent decades, with aggressive biocides such as Tributyltin, which have been used in self-renewal paints. There are now numerous paints with low volatile organic compounds, as well as paints which have been mixed with oil and water basis.
In the past few years, so-called ultrasonic antifouling has become a very realistic alternative. It works by emitting pulsed ultrasonic frequencies via transducers on the inside of the trunk. Thus, a layer of mobile water molecules is created on the entire underwater profile of the hull, which is intended to prevent microorganisms from settling and thus counteract the evil at the root. For a large boat, however, this is a rather expensive fun, because several converters have to be used and you need a reliable power supply. However, regarding fuel savings in the operation of your boat, not to mention the cranks and cost of properly cleaning the underwater vessel and the proper disposal of the sewage.
Proactive behavior of the skipper
If a boat with a glide is calm in the water, it is the buoyancy that keeps it above water. But when it starts to move forward, we (at least initially) become a displacer. In other words, to put a boat length back, it must push aside a quantity of water corresponding to its weight. As the speed rises, the shape of the fuselage produces more and more buoyancy, which lifts the fuselage over the water surface and radically reduces the displaced water volume. This buoyancy finally reaches a hydrodynamic equilibrium, whereby the boat glides on a small section of the aft fuselage area and thus only has to accept very little resistance.
However, this balance can be quite unstable. If you plane the boat too much, it is lifted too much from the water, reducing the surface of the hull in the water so much that it can no longer support the weight of the boat. The result: the bow goes up and down, the boat begins to stomp without wave influence. On the other hand, if there is too much hull in the water, the friction resistance increases, which hinders or slips the glide, which slows the boat and plows through the water like a semi-skid. The optimum compromise between control and efficiency is nothing but the continuous balancing of hydrodynamic buoyancy, speed, and trim. And that is exactly what you are called for as a skipper.
It is ideal to be on the road with a clean, well-trimmed boat and only have to give so much gas that the optimum performance is achieved. Each boat has a different “sweet spot” that is dependent on weight, propeller selection, the ratio of length to width, trunk shape, reclining, trimming and many other factors. Fortunately, all this can be determined relatively easily on your boat. You only have to spend a few minutes to gradually increase the revolutions per minute during the journey, beginning at 500, to the very end of the scale, constantly checking the fuel consumption at the flow meter and the speed at ground level at the GPS. If you know the tank capacity, you can calculate the optimum range of these values. This occurs in a pattern which can be visualized with a curve that is most likely to drop drastically between 80 percent and full throttle and shows a range of the ideal rotational speed which should be between 60 and 75 percent, or for modern outboard engines between 3,600 and 4,500 rpm/min. If you move your boat within these parameters, you are quite well.
However, the speed range is only a part of it. You must also work on the optimal trim of the boat, not only with the angle of the motor (with external brackets) and the trim tabs but also with the correct weight distribution, where most pounds should be stowed far down and centrally (similar to the keel a sailing yacht). Avoid carrying excess luggage and large fuel reserves if you do not need them. Steer them in focus and take a look at the side of the waterline to see how far the fuselage gets out of the water. Listen to the sound of the engine revolutions, get an idea of the boat’s floating position and develop a feeling for the “sweet spot” of your boat.
For longer trips, when it comes to miles and not ruling, it is worth to have the tide on its side. Choose in low-priced weather, so you are not forced to take a defensive zigzag course. It is also recommended to navigate as precisely as possible between the individual waypoints. All this is trivial, but distributed over a whole season, the positive effects achieved can help save quite nicely.
Use other electronic instruments on board, especially your navigation software. The old geometric rule of thumb, which has been introduced into the school, namely that the shortest link within two points is a straight line, also applies to the water.
If you are only one or two degrees away from the ideal line on long passages, you will have to take a detour that costs both time and fuel. A distance of 10 additional miles can mean 80 liters of additional consumption, depending on the boat and the conditions. Use the chart plotter to get the shortest course and look forward to the savings you earn.