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Do you have a boat with an outboard motor, but you are not sure what the maximum speed is? Unfortunately, that cannot be said exactly. It depends on many factors, such as the material of the boat, its size, weight, age, the shape of the underwater hull and maintenance. This makes it difficult to say how fast an outboard motor can go. What we can calculate is the hull speed of a boat. We are happy to explain more about the advantages and disadvantages of hull speed and how to calculate it.
Hull speed is the highest speed a boat can reach under normal conditions. This speed is determined by the amount of water displaced by the hull of the boat (the underwater hull). When the boat is sailing at hull speed, a bow wave is created in front of the bow of the boat: the water is pushed away and moved backwards. If the hull speed is exceeded, the boat will plane. In this situation the boat no longer sails through the water, but over the water. The following image illustrates the different stages of this process.
The hull speed therefore indicates the maximum speed that a boat can reach under normal conditions. It is useful to know this speed. By cruising between low speed and hull speed, the boat uses significantly less power, which saves fuel and is more durable.
When the hull speed is exceeded, it is difficult to go any faster. This is because the boat cannot catch up with its own bow wave; he cannot sail faster than the speed of this wave. In this case, adding extra power only leads to more water displacement. The hull speed therefore forms a physical limit for the maximum sailing speed. So it is better to avoid hull speed if you want to sail fast and plane.
Do you want to know what the hull speed of your boat is? You can easily calculate this with a simple formula. Multiply the square root of the boat’s waterline in meters by 4.54. For a 9 meter boat this means that the hull speed (√9=) is 3 x 4.54 = 13 km/h. For a 16 meter boat, the hull speed is (√16=) 4 x 4.54 = 18 km/h. Please note: this calculation only provides an estimate.
Sailing at a high hull speed has both advantages and disadvantages.
It is more difficult to gain speed because the boat cannot ride over its own bow wave. The boat is then ‘trapped’ in water displacement.
To return to the outboard motor: power is often expressed in horsepower. Maybe kilowatt (kW) means more to you. Fortunately, it is easy to convert horsepower to kW. 1 hp equals 0.74 kW. If you buy a 25 hp outboard motor, it will have approximately 18 kW.
You can also calculate it the other way around: 1 kW equals 1.36 hp. If you have an outboard motor with 90 kW, it has approximately 120-125 hp.
The maximum speed of your boat including outboard motor is difficult to say. Factors such as the boat’s material, size, weight, age, hull shape and maintenance all affect speed. There are certain apps and tools that can calculate your speed during your boat trip. What you can also do is divide the number of kilometers traveled by the time it took you to get to your final destination. For example, if you sailed 50 km in 1.5 hours, your average speed was 33 km per hour.
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It's impossible to say exactly. It depends on many factors, such as the material of the boat, its size, weight, age, the shape of the underwater hull and maintenance. What you can do is divide the number of kilometers traveled by time.
Hull speed is the highest speed a boat can reach under normal conditions. This speed is determined by the amount of water displaced by the hull of the boat (the underwater hull).
You can use a simple calculation to calculate the hull speed: multiply the square root of the ship's waterline in meters by 4.54. A 16 meter boat therefore has a hull speed of (√16=) 4 x 4.54 = 18 km/h.
The hull speed is caused by the amount of water pushed away by the underwater hull. When the boat sails at hull speed, a bow wave is created in front of the bow of the ship. The water is pushed away there and moved to the rear.
1 hp equals 0.74 kW. If you buy a 25 hp outboard motor, it will have approximately 18 kW.
1 kW stands for 1.36 HP. If you have an outboard motor with 90 kW, it has approximately 120-125 HP.
