The Best Engine For A Ski Boat: Power And Performance

When it comes to ski boats, there are several types of engines to consider. The most popular type of engine is the outboard engine, which is powerful, quiet, and lightweight. Outboard engines are also known for their excellent manoeuvrability, making them well-suited for water sports. Another option is the inboard engine, which is located inside the hull of the boat and is less popular due to its impact on stability and manoeuvrability. For those seeking sustainability, diesel-powered engines are an option, offering outstanding durability for frequent use. The size of the engine will depend on factors such as the length, weight, and hull shape of the boat, as well as the number of people on board. Jet drives are another option, using water to propel and steer the boat by changing the direction of the water stream.

Outboard boat engines

Two-stroke outboards offer up to 300 hp, while four-stroke outboards typically offer up to 350 hp, with one option providing 557 hp. Direct-injection two-stroke outboards are more environmentally friendly than older carbureted models, and they have become much more reliable in recent years.

Outboard engines are available from a variety of manufacturers, including Yamaha, Honda, Suzuki, Mercury, and Tohatsu. When choosing an outboard engine, factors such as shaft length, fuel delivery system, and horsepower should be considered to ensure it meets your specific needs.

For water skiing or wakeboarding, the required engine size depends on factors like the length, weight, hull shape, and number of passengers on the boat. As a general rule of thumb, a five-metre boat will need at least 60 horsepower, while a six-metre boat will require around 100 horsepower, and a six-and-a-half-metre boat will need approximately 150 horsepower. Consulting an expert is recommended to ensure you select the appropriate engine for your specific boat and activities.

Inboard engines

Inboard boat engines are installed inside the hull, either in the bilge or in an engine room for larger vessels. They are enclosed within the hull of the boat, usually connected to a propulsion screw by a driveshaft. Inboard engines require one or more rudders for steering, which are located behind the propeller that drives the boat. This means that boats with inboard engines are steered with a wheel rather than a tiller.

There are two main types of inboard engines: direct-drive (D-drive) and V-drive. In D-drive systems, the engine faces the rear of the boat and is connected to a drive shaft that protrudes out of the bottom of the boat. This type of engine minimizes power loss and is highly reliable. However, it may need to be placed further forward in the boat, reducing the amount of space available for the cabin and seating.

V-drive inboard engines, on the other hand, face forward and have a transmission that redirects the drive shaft towards the stern, creating a V shape. This configuration provides more space in the cabin or additional seating, as the engine is placed further back in the boat. However, some efficiency is lost between the engine and the propeller due to the change in direction.

Stern drive engines

MerCruiser offers a range of stern drive engines, from the 4.5L V-6 with 200 to 250 horsepower to the 8.2L V-8 producing 380 to 430 horsepower. They also have a line of diesel engines that can be rigged with their stern drives, including the 2.0L in-line-four, 3.0L V-6, and TDI 4.2L V-8 models.

Volvo Penta, credited with introducing the production stern drive in 1959 with the Aquamatic, offers a similar range of gasoline and diesel engines. Their gasoline engines start with the 4.3L V-6, producing 200 to 280 horsepower, and go up to the 6.2L V-8 with 380 to 430 horsepower. The diesel line includes the D3 (2.4L), D4 (3.7L), and D6 (5.5L) models, available in various horsepower configurations.

Jet drive engines

The jet drive system is commonly used in personal watercraft (PWC), also known as jet skis, and provides versatility, simplicity, safety, and speed. The absence of propeller blades makes it safer for swimming behind the boat and reduces the risk of injury. Additionally, jet drives have excellent off-idle acceleration due to the enclosed impeller design, which focuses the energy of the thrust.

One drawback of jet drive engines is the lack of a true neutral gear. Engineers have worked around this issue by creating a neutral setting that combines forward and reverse thrust, resulting in the boat moving slightly. Another limitation is the need for thrust to steer the vessel. Reducing the throttle to zero results in a loss of steering ability, which can be counterintuitive and challenging for those accustomed to traditional marine propulsion systems.

Despite these drawbacks, jet drive engines are versatile and can be found in various applications, from recreational boats to large passenger ferry boats. They are particularly useful for high-performance applications and shallow draft conditions, making them a popular choice for ski boats and other water sports vessels.

Diesel engines

While gasoline engines are more common, diesel engines are also an option for ski boats. Diesel engines offer greater durability if you plan on using your boat frequently and can be a good choice for heavier boats that need more power. They are also more fuel-efficient than gasoline engines. However, diesel fuel can be harder to find and more expensive than gasoline.

One example of a diesel engine for ski boats is the Craftsman Marine engine, which is built on a Mitsubishi base. This engine is known for its quiet and vibration-free operation and complies with the European Recreational Craft Directive (RCD). Craftsman Marine offers other sizes of marine diesel engines as well.

In addition to purpose-built diesel engines, it is also possible to convert existing ski boats to run on diesel fuel. For example, some ski clubs in the UK have converted their boats to run on LPG, which is cheaper than gasoline since it is not taxed as a fuel source. However, as one ski boat owner found out the hard way, filling a gasoline-powered boat with diesel fuel will not end well!

Frequently asked questions