Better an OUTBOARD or a STERNDRIVE?
This post is done thanks to a client who has been for different reasons trying to put a small inboard 2 strokes diesel as old as Jesus on a dinghy… Noel this is for you 😉
Let’s begin in saying that this is a question which remains for a dimension of rhibs which starts to be valid over 8m as for the structure and the width of the hull would not be possible otherwise. The reason is one of the first point we are gonna touch but let me tell you something you probably didn’t know…
All because of an icecream
It was the request for ice cream expressed by a young lady that prompted Ole Evinrude to row across a lake during the hot summer of 1906. That day was particularly sultry, so much so that the rowing crossing was a long, tiring and sweaty undertaking: E moreover, when the brave Ole showed up again, in a pitiful state in front of the delicious Bess Cary, the ice cream was not much better than him. It was at that moment that the young American wondered why no one had ever thought about putting an engine on small rowboats. After three years of development the first Evinrude outboard was built in 1909. That same year the 15 engines made were all sold immediately. In 1910, 1000 copies were sold and the following year the number doubled. The Evinrude became the first mass-produced outboard motor.
Outboard or Sterndrive?
Almost everyone in life, at least once, has participated in a discussion about which engine is the best. A nice stern foot with the propeller in the compartment and the stern platform, or a powerful outboard, all locked up under the grille, hooked to the mirror?
The Hamletic doubt has already been widely debated by experts, technicians, Sunday boaters and long-time captains. So why do we, too, feel the need to add ourselves to the discussion? Because things have changed, in the sense that the engines are no longer the same as they were a few years ago. In the past, outboards were only installed up to a certain size of boat or dinghy.
If the length increased, it was necessary to switch to a sterndrive. Today this is no longer the case, because the sterndrives are less and less bulky, less heavy and able to fit into small engine compartments, while the outboards are more and more powerful, just think of the 627 horsepower of Seven Marine, the English company acquired. by Volvo Penta. Seven Marine represents the tip of the iceberg, but it is not that the other manufacturers are much less.
In addition to Mercury, which has reached 400 hp, there are Suzuki and Yamaha who have 350 on the list and even Honda is studying a new 350 model that should make its debut at the Miami Boat Show next year. What about Mercury’s new V6 and V8? Is it science fiction to think that in the near future, with such a large volume, a volumetric compressor will be added and we will get many more horsepower than we have today? Let’s try, then, in the light of the growth of the outboards upwards and the sterndrives downwards, to deal with the topic. And we try to do it data in hand, that is, by comparing the performances we recorded during our tests.
For acceleration and top speed, outboards definitely come out better. The theory is supported by practice. Let’s consider two very similar boats in size and engine power: Ranieri Next 370 with two Mercury 400 hp each and Invictus 370 GT with two MerCruiser 370 hp.
It is true that Ranieri’s model has 60 hp more, but the acceleration was very intense. In less than 4 seconds it glided and reached the maximum in 22. Invictus with the sterndrives took 7 seconds to raise the hull and 27 to reach the maximum. Consumption also changes because the two Veradoes at full throttle consume 285 liters / hour in total, while the two MerCruisers drink just over half, or 158 liters / hour.
The question to ask is: how often do you go at maximum speed? Is the boat used for day trips or for longer range sailings? If cruising prevails, a stern drive may not necessarily be better than an outboard, especially in terms of fuel consumption.
Furthermore, it is easier for an engine mounted inside an engine compartment to have a better trim. On the other hand, with the same power, it has a heavier weight than an outboard. As far as maneuverability is concerned, both engines now have a maneuvering joystick. Therefore, those who have a double installation, will be able, with the addition of a lot of money on the list price, to make use of this technology.
An engine that pushes more than another, but consumes less has not yet been invented. Many things can affect consumption, starting with the trim, the propellers, the number of passengers on board, up to the sea conditions. Despite this, generalizing, it can be said that, especially at mid-range and cruising speeds, it is possible that a sterndrive consumes less than an outboard.
Take for example Bénéteau’s Flyer 8.8 with I.C.’s 2 × 200 Suzuki and Aquilia Yacht with 2 × 220 hp Volvo Penta. The latter measures half a meter more than that of the French shipyard, but the weights are similar, given that when empty the difference is just 100 kg.
Consumption with the two Volvo sterndrives is lower. At 25 knots the savings are about 20 liters / hour. The two Suzukis need 60 liters, while the two stern drives are satisfied with 40. At 30 knots the difference is even more evident: more than 100 liters with the outboards and just over 50 with the two Volvos.
For consumption, the type of fuel must also be taken into account: diesel or petrol? In the outboard world, the first diesel fueled was Ruggerini Marine about thirty years ago, but it was not very successful. It has recently made a comeback. There is the German Neander Shark, produced in collaboration with Selva Marine and distributed by Yanmar, Mercury which launched the 175 dsi last year and the English Cox with its 300 hp diesel model.
On paper it weighs about the same as Yamaha’s V8, but the dimensions are truly exaggerated. Weight and dimensions do not make us think that diesel outboards can have a mass diffusion in pleasure craft. Often born as military supplies which are then converted to civilian use, but are especially suitable for inflatable boats or commercial or work boats that grind many hours of motion a year.
The situation regarding the sterndrives is different, even if only partially. Also in this case you can choose between diesel or petrol because there are many stern drives powered by engines of one type or another. However, the advice to reflect on the miles that presumably will cover is valid.
Outboard or EFB A diesel EFB is more expensive than a gasoline and therefore the game is only worth the effort if you plan to sail a lot, otherwise the initial cost is not offset by the savings in fuel price. The difference in cost between a diesel model and a petrol model for a boat of about ten meters in length can reach or exceed 20,000 euros.
Is it worth it? With 20,000 euros, more than 12,000 liters of petrol can be bought. How long does it take you to consume 12,000 liters of fuel? Three, four or ten years? The choice between diesel and petrol also depends on how much you use the boat. Of course, data in hand, if you don’t look at the price list, there is no comparison.
A concrete example comes from Frauscher’s 747 Mirage. We had the opportunity to test it with MerCruiser 350 MAG and a Mercury Diesel TDI 4.2. Identical boats, different engines. Both sterndrives, but the 370 hp diesel and the 300 hp petrol. The diesel won hands down and not just for the extra 70 hp.
He pushed the 747 Mirage up to 50 knots, while on petrol we stopped at 44 and it consumes even less. At 40 knots of speed, the diesel needed 52 liters / hour, while the petrol consumed 76. The acceleration performance was very close: only a second of difference both for gliding and for reaching maximum speed. Therefore? Better diesel? Yes, if you don’t take the price into consideration. In the price list, the petrol MerCruiser cost just over 20,000 Euros including VAT, while the diesel exceeded 52,000.
The clash, in this case, is won by the outboard motor. The sterndrive includes more interventions and is subject to greater wear. Headphones, for example, both those that protect the gimbal and those that repair the exhaust gas, suffer from marine corrosion. Approximately every two years, they must be replaced.
If you sail in fresh water, the duration obviously increases significantly, possibly reaching four or five years. Furthermore, the advantages of the outboard are that often the foot, even when the boat or dinghy is in the water, can be lifted and remain dry. The stern drive, on the other hand, needs a good antifouling to avoid encrustations and dog teeth.
With proper maintenance and servicing every 100 hours with replacement of liquids, filters and spark plugs, they make the outboard almost indestructible, especially if the winter passes it dry and indoors. The sterndrive also gives ample durability guarantees with wintering and ordinary maintenance, but this is certainly more expensive.
Also as regards the overall dimensions, there are strengths and weaknesses for each engine. The stern foot offers the possibility of a large stern beach. The power unit is all in the engine compartment and the foot is submerged in water. The whole can then be covered by increasing the walkable surfaces and creating a very comfortable platform for entering and exiting the water.
The same thing can be considered a defect. Being in the engine compartment, in fact, there will be less space to devote to the lockers. The essential difference is perhaps all here. De gustobus. Yachtsmen who want the cockpit clear, perhaps for fishing or for sporting activities in general, will be more oriented towards the outboard.
Those who, on the other hand, prefer the cruising use of the boat, will find greater satisfaction with a sterndrive covered by a small beach at the stern.
Even more than once, when choosing the best engine, your preferences and the type of use you intend to make of the boat or boat count. There are no longer the imposed choices, when if you had a small hull you had to orient yourself towards the outboards and if the boat increased in length, the only possible engine became the stern drive. Today, thanks to the new outboard and sterndrive models, the choice is up to you (or the shipyard).
- the classic platform can be installed at the stern
- engine almost invisible because it is inserted in the compartment
- harder to steal than an outboard
- on average, quieter if the soundproofing of the compartment has been done in a workmanlike manner
- simpler and less expensive maintenance
- easier to repower
- lighter for the same power
- no clutter in the engine compartment