The lower the fuel consumption is the happier the captain gets.
Saving fuel is an issue that «burns» all of us, especially when on our transom one or more high-horsepower outboard engines are mounted.
It is very well known that the most economical performances in modern outboard engines are observed when they operate between 3000 and 4000 rpm corresponding to cruising speeds of about 20-35 knots.
At this range of rpm besides, we mostly operate our engine or engines since at this range we use to travel especially when we have to cover long distances.
So we will try to explain the ways to reduce the fuel consumption at low and medium rpm focusing of course on the factors that we can change.
We should always keep in mind that the following important parameters will help us to improve our fuel mileage:
One of the major factors that affect the overall performance of our boat-engine combination and its fuel consumption is our propeller itself.
By matching the right propeller is sure that we can improve our boat’s fuel economy. But we never forget that the propeller which will eventually choose should allow the engine to reach at least until the middle of the maximum rpm range recommended by the manufacturer.
Propellers with larger diameter are generally getting better fuel economy at low and medium rpm than the relevant ones with smaller diameter, a fact due to their less slippage.
When we are switching from a smaller diameter propeller to a larger one we just have to reduce its pitch in order to retain the same engine’s rpm.
Indicatively it is mentioned, always relying on our test data, that a larger diameter propeller can easily achieve 30% lower fuel consumption than a smaller diameter one. A typical example is the much lower fuel consumptions of the Eco Enertia compared to the Tempest Plus, the Mirage Plus or the Revolution propeller.
Switching from a shorter pitch propeller to a longer pitch of the same brand it is almost sure that we will achieve greater fuel economy at the midrange rpm. Suffice off course our engine’s rpm at wot to be near at the middle of its maximum rpm range.
Let’s suppose for example that the maximum rpm range of our engine is between 5700-6300 rpm and the propeller we have matched is the Revolution 19" which allows our engine to reach 6300 rpm.
In this case we can switch to a Revolution 21", especially if we want to cover a large distance, thereby increasing our cruising speed at the midrange rpm while reducing the fuel consumption. Of course our engine’s rpm will drop but they will still remain near the middle of its maximum rpm range.
The reduction of the fuel consumption at medium rpm is noticeable when we increase the pitch of our propeller by 2 inches.
But beware! We must not fall into the trap and increase the propeller pitch further due to the even greater fuel economy, sacrificing the boat’s performance at low rpm, as well as the proper operation of our engine, the rpm of which will drop very low.
The 3-blade propellers provide usually better fuel consumption than the 4-blades of the same diameter; except of course when we are carrying heavy loads.
The reason is the additional drag generated by the extra blade of a 4-blade propeller.
We all know that there is no ideal engine mounting height for each use as the height of the engine on the transom depends on many factors interacting together.
In general the engine is better to be mounted as high as possible, but on that point in which the boat performance at low rpm will not be suffered.
Raising our engine to the highest possible position, the immersion of the lower unit is reduced. In other words there is less gearcase in the water which means better fuel economy due to its reduced drag.
At this point it is important to emphasize the value of using the power lift, which enables us always to have the ideal engine height so as to achieve the maximum fuel economy in relation to the way we use our boat and the conditions we operate it in.
It is noteworthy that the proper engine mounting height in combination with the proper propeller can give us up to 50% lower fuel consumption!
The proper adjustment of the engine’s trim during our ride determines the boat’s attitude, the angle i.e. of our bow related to the surface water, which affects significantly, among other things, the fuel consumption.
Knowing in advance in which rpm range of the engine we have the greatest economy while underway, we only have to push the throttle lever until the engine reaches the desired rpm while adjusting the trim in the proper position.
But what is the proper position of the engine’s trim?
Certainly an experienced captain is able to determine the proper position of the trim just observing where the hull cuts the water looking the spray that exits from its either side, watching the wake of the stern and listening to the sound of the engine.
If we don’t belong to the above category then it would be wise to experiment several times with the engine trim while observing the indications of the tachometer, the Gps and the flow scan so as to achieve the best combination of speed and fuel consumption.
When the conditions and our loads permit, our engine shall be trimmed neither too far down nor too far up. We are trimming out the engine so as to bring the A / V plate parallel to the water surface and our propeller running alongside it. Usually the best trim position is a little bit higher than the point referred as above, where we achieve to reduce the exposure of the lower unit in the water while by raising the bow, at the same time, we try to keep the most possible part of the hull out of the water minimizing the amount of its wetted surface.
All the referred above lead to the most efficient running angle, minimizing the drag and improving the fuel economy maximizing thus our mileage.
However, be careful! Don’t trim up too much!
If you have trimmed out your engine too much the propeller will tend to lose its bite and aerate leading to negative results in both the speed and the fuel consumption.
The heavy load and the unbalanced weight distribution are the enemy of the center of gravity and the right attitude of a boat.
The weight and the weight distribution on board affect more than any other factors the fuel consumption. This is why we have to be particularly careful of the carrying loads and the placement points.
The extra load increases the wetted surfaces of the hull resulting to greater drag and fuel consumption. The heavier the load is, the more the fuel burn gets.
It is a fact that most of us usually take aboard much more load than we really need.
So remove everything you don’t need and load only what is necessary on each trip. No need for example to carry extra refrigerators or spare anchors with many meters of chain when we will not need them. No need to travel with fuel and water tanks full when not travelling long distances. This of course does not mean that we are risking our safety for the sake of lower fuel consumption.
But even more important than the carrying loads is where they are located on board. By storing additional weights in the wrong places we change the boat’s center of gravity destroying the right relationship of center of gravity-engine mounting height thus virtually cancelling the operation of trim.
The small and all stepped boats are more sensitive to centre of gravity’s changes which affect greatly the attitude, downgrading thus the quality of the ride and increasing the fuel consumption especially in bad weather.
So, take care of the right boat’s attitude and save fuel by storing the heavier objects around the center of gravity and on the aft third of your deck, placing the less heavy towards the bow. Keep the bow light so as to be able «to listen» the trim settings and stay high and dry during riding.
The overload and the unbalancing weight on board kill the ride.
We know very well that a clean and polished hull is more slippery, goes faster and maximizes the fuel economy.
Many times we have noticed sudden reduction of our engine’s rpm, decrease of the speed and increase of fuel burn due to the additional drag created by a fouled bottom.
It is very important therefore to maintain our hull’s gelcoat in excellent condition and free of fouling in order to get the maximum performance without wasting fuel unreasonably.
Apart from the above mentioned factors there are many others which play an important role in fuel efficiency such as:
By handling the throttle smoothly, avoiding sudden accelerations and aggressive driving, maintaining steady course and constant speed is sure to improve fuel economy.
Avoid traveling with bad weather conditions because the strong headwinds and rough seas create additional resistance while forcing us to constantly deviate from our course and fluctuate our speed. If it is possible choose to travel having the sea on the quarter achieving greater economy.
We will never get the optimum fuel economy if we don’t know our boat very well, if we don’t handle it with the right way or if it is not properly rigged.
Think about how many hundreds of miles we cover every season and calculate how much money we can save by implementing the above ways to reduce fuel consumption.
At the 61st Genoa Boat Show we had the opportunity to test the new beastly 7.6-liter, V12 and 600-horsepower Verado outboards mounted on the MAR.CO R-Evolution 36, a...
Read moreAs we have already mentioned in our related articles, the use of trim tabs is of great importance on each Rib...
Read moreIt is a fact that a spare propeller is one of the most important elements of the basic equipment of every boat and is really important for our safety, especially if we are used to making long...
Read moreThere is no doubt that a stern anchor is one of the basic supplies that we shall always have on board and therefore one of the elements of the necessary equipment that every boat...
Read moreIt is true that lately the inflatable boats have grown up to 50 feet in length. As a result, their equipment, such as refrigerators, freezers, heaters, microwaves, etc., have also
Read moreOne or two outboard engines? That’s an essential dilemma that concerns many sea-friends who have decided to buy a larger rigid inflatable boat. And the answer is...
Read moreDo you want to buy a rigid inflatable boat (RIB) but you do not know how to go about it? Worry no more. This article will guide you on what to consider in making the best possible...
Read moreIt would not be an exaggeration if we said that it is wonderful and sometimes even fascinating to have the required basic knowledge so as to be able to setup a boat...
Read moreIt is true that we often hear about «great» captains who «flatten» the waves with their unbelievable Ribs, even waves created by winds of 7 or 8 bf. Of course, they never talk...
Read moreEvery year we have always the same problem: “how can I clean my Rib without damaging its tubes’ surface?” Here it is a complete tutorial for the restoration of your inflatable boat...
Read moreEach time we are going to tow our Rib, it is necessary to check thoroughly the trailer to ensure not only our own safety but our beloved inflatable boat as well...
Read moreHaving completed the maintenance of your engines, which must remain in a vertical position in order to drain well from the water, we proceed to the maintenance of the Rib...
Read morePlease, do not abandon your passion! The water, and especially the saltwater, corrodes everything while the immobility accelerates the wear...
Read moreThe word «raid» has the power to bring to mind mysterious islands and unlimited rides to every devotee of ribs deserving this title...
Read moreMany of us, at the chase of the ideal propeller, have tried quite many of them looking for the ideal one for our rib-engine combination...
Read moreAs it has already been mentioned, there is no the ideal engine height suitable for any combination of hull, prop and load but each...
Read moreEvery year about this time, boaters across the country start to get the itch. The days get a little longer, and a little warmer, and it just..
Read moreI’ve heard steering cables should be «maintained». How exactly is this done?
Read moreAs spring slowly approaches, it’s time to start planning for boating season. In order to make sure your boat is safe and running efficiently...
Read moreTaking into consideration the ancient Greek saying «Prevention is better than Cure», it would be appropriate to check our RIB and our engine every time we get out of the sea. It...
Read moreAs we have seen in the previous article entitled «Engine’s mounting heigh», one of the most important factors affecting a lot the boat’s performance is the engine’s mounting...
Read moreNowadays, as the increase of the cost of fuel has become one of the major factors for the choice about the proper outboard, Suzuki has
Read moreAs we have seen in a previous article, the trailing edge of the trim tabs should be slightly higher than their front edge when they are fully retracted. This slight upward...
Read moreThe lower the fuel consumption is the happier the captain gets. Saving fuel is an issue that «burns» all of us...
Read moreThe Maritime knots and their use II. The Cleat hitch and the Highwayman’s hitch...
Read moreBefore we go out to the sea with our boat, it is necessary to know some basic knots that will mainly help us to tie with safety...
Read moreA few days ago we had the joy to meet Gianni Di Meglio, one of the most famous offshore powerboat racers in Italy and…not only. Any...
Read moreThis project was born some time ago in the one of the most beautiful places of our beloved Italy, standing in the wonderful...
Read moreAny obstacle to the constant flow of fuel from the tank to the engine is sure to immobilize us. It is indeed...
Read moreAs we have seen in previous articles, the application of trim tabs is particularly useful to any boat. They improve hole shot, boat’s...
Read morePerhaps there is nothing more exciting than the time we take our place behind the cockpit, our hand pushing the throttle and the bow...
Read moreIt is known that the outer surface of a hull is covered by a special resin called gelcoat, which mainly protects it. Thus, this gelcoat...
Read moreBy the term of deadrise we mean the angle which is formed between the horizontal plane and the side of the hull, at its any point...
Read moreIt is a fact that every manufacturer of outboard engines installs different gear ratios while we see that as the horsepower decreases the gear ratio gets higher...
Read moreThe torque that is produced by the engine is converted to thrust by the combined effect of the gear ratio with our propeller. Physics...
Read moreThe propeller rotates at the same speed with the propeller shaft, while the propeller shaft usually rotates much slower than the engine...
Read more