Center console boats from 20'' can usually perform well with a single outboard from to hp, depending on load and top speed expectations. Over 25'', twin engines are typically recommended. Consumer Caveat: Buyers should remember that most boat tests are done with just two people aboard. All small boats are weight-sensitive, so owners planning on loading a boat with guests should plan on robust power options. Big Single or Smaller Twins?
All outboard engines are much more reliable than they were 15 years ago. As a result, many offshore anglers are opting for the advantages of a larger single rather than smaller twins, equaling the same horsepower.
Twins will weigh more and burn more fuel at a given RPM and speed -- thus reducing range. On the other hand, some anglers feel more comfortable offshore with redundant power. Take your pick. Whether or not all of this expensive iron on the transom is necessary is a matter for the individual buyer to decide depending on his or her mission. Make sure you know what octane fuel your large outboard is recommended to run on. Some require high test fuel.
For the last decade, pontoon boats have been the most popular type of boat on the market. The invention of the tri-toon and new center console designs have made pontoon boats faster so that they can now be used for skiing and towing, in addition to cruising and entertaining. Most pontoon boats have twin toons and these are displacement boats; they can only be pushed so fast and adding big engines will not make them go faster and is counterproductive.
Depending on how large and heavy the twin toon is, most can be pushed close to their maximum speed with a single hp engine, and many people are quite content with a hp engine driving their toons. Tri-toons are another story. Because of their added buoyancy, these boats can get up and plane and typically have WOT speeds in the mph range.
Some new tri-toons can go 55 mph to 60 mph when powered with twin hp engines. There is even one large pontoon boat on the market with triple hp engines. They can be powered with hp to hp single engines. Towing Considerations: Owners wishing to tow water skiers or wakeboarders must buy a tri-toon. Because all tri-toons are hard to get up to what we might consider "planing speeds," an engine with strong low-end torque is advisable. Do you want to go 75 mph or 7 knots?
Torque is easiest to explain through an example. Imagine you have a large socket wrench with a two-foot handle.
Keep in mind, with that calculation, you could get the same result — pound-feet of torque — by applying one pound of force to a socket wrench with a foot handle, or by applying pounds of force to a socket wrench with a one-foot handle. In an engine, torque produces power — so being able to relate it to horsepower is critical. A device called a dynamometer applies a load on the engine and then measures the amount of power it produces to determine torque.
Marine dynamometers are available, too — taking into consideration boat operation by simulating on-the-water operation. The divisor, 5,, comes from a series of calculations that convert rpm to radians per second. Engines will have a point in rpm at which the power available from the engine has reached its maximum. In addition to giving you a maximum for passengers and cargo, the manufacturer will also spell out the absolute maximum boat horsepower.
The boat horsepower-to-weight ratio is simple to calculate and can be expressed in horsepower per pound or pounds per horsepower. Taking 5, divided by gives you a result of Doing the opposite calculation — taking divided by 5, — gives you a result of 0.
The lower the number, the faster your boat will go. While one or two outboards may give you the same horsepower result, keep in mind additional weight will accompany each additional outboard motor. The amount of horsepower you choose will impact your fuel efficiency. According to Boating magazine , running your gas engine between 3, and 3, rpm and your diesel engine at three-quarters throttle is the sweet spot for fuel efficiency. Keep this fact in mind as you consider what horsepower to choose.
For those who prefer exact calculations, Boating magazine has provided some calculations you can use to run some of the numbers. To do this, you need to know gasoline weighs approximately 6. You also need to know a well maintained four-stroke gasoline engine is estimated to burn about 0.
For example, if you want to determine the fuel consumption for a horsepower gasoline engine, you would calculate 0.
As with most decisions related to boating, the use of the boat is always a factor. Are you using the boat just to cruise with friends and family? Or will you be pulling water skiers, wakeboarders and tubers? The addition of pulling someone behind the boat — and the additional weight of storing watersport accessories — increase the need for power and are often a reason to consider adding horsepower to your boat.
All Rights Reserved. Parsun Outboards Motor Size Guide. Tips for selecting the right size hp for portable outboard motor for your boat. What you can expect: Will propel most hulls at approx kmh In auxiliary or kicker motor applications, hulls less than kg and under 4.
What you can expect: Engines in this range will propel most hulls at approx. We have had no problem with these motors and would recommend them to anyone. Social Media: Facebook. If you want high-speed, you'll need plenty of power.
Depending on the size and weight of your boat, your hull design, and how much cargo you are carrying, you can figure you'll need to hit mph just to get your craft on the plane.
If there's one point of discussion in the world of outboard boat motors, it's the debate between 2-stroke and 4-stroke motors. In reality, both are good choices. Which is best for you depends on what features are most important to you. Do you want 2-stroke electronic fuel injection EFI?
Or an old-school 2-stroke carbureted model Effective July 1, , U. Each motor type has its advantages and disadvantages depending on the type of boat you have and how you want to use it. Take time to learn about them and decide which type is right for you. For example, 2-strokes are generally lighter for the same power and offer a better, faster throttle response, but they also tend to throw more vibration and noise.
And, while 4-strokes may be larger and heavier, they're also quieter, often have better fuel efficiency and generally offer better speed control. Most inflatables will require a 15" short shaft, while fishing boats and yacht auxiliary motors require a long shaft. If you're not sure what length shaft you'll need, here's how to find out.
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