Small Boat Engines: Choosing The Right Sea Power

Small boats are a great way to get out on the water and explore. They are less expensive than larger boats, easier to tow, and can access tiny waterways. When it comes to choosing an engine for a small boat, there are several factors to consider, including the size and weight of the boat, the type of engine, and the intended use of the boat. The right engine is crucial—too small and the boat will lack speed, too large and it can damage the vessel. A good rule of thumb is that a boat needs one horsepower for every 25 to 50 pounds of vessel weight. So, for a small boat, an engine with 20-60 horsepower would typically be sufficient.

Electric vs. gas motors

Electric motors for small boats have many advantages over gas motors. They are much quieter, which makes for a more enjoyable journey and is also beneficial for anglers, as the noise won't scare fish away. Electric motors are also more powerful than trolling motors and are more efficient and environmentally friendly, especially when trolling at slow speeds. They are lightweight, portable, and easy to start, with a simple electric throttle. They are also clean, with no petrol leaks or stains, and can be solar-powered.

However, gas motors have their benefits, too. They provide higher power output, making them suitable for medium to large boats and demanding water activities. They are also better for long-distance journeys, as they have extended range capabilities and do not need to be recharged like electric motors.

Electric motors are initially more expensive than gas motors, but the former's longer runtime and lower maintenance costs make them a more cost-effective choice in the long run. Gas motors require regular maintenance, including oil and filter changes, and fuel system checks, which can increase overall ownership costs.

Electric motors are ideal for short trips and freshwater use on small to medium-sized boats, while gas motors are better for long-distance and heavy-duty use.

Outboard, inboard and stern drive engines

Small boats are a great way to discover a love for the water. They are less expensive than larger boats, easier to tow or load, and can access tiny waterways that bigger boats cannot.

There are three types of engines for powered small boats: outboard, inboard, and stern drive engines. Each has its own advantages and disadvantages, and the best choice depends on the activities you plan to do with your boat.

Outboard Engines

Outboard engines are mounted on the transom of the boat, outside of the boat's hull. They are used to both power and steer the boat. On smaller boats, a hand tiller is used to steer, while larger outboards use a steering wheel to adjust the direction of the engine. Outboards can be lifted completely out of the water, allowing access to shallow areas. They are also easy to work on as the engine is exposed and out of the water. They do not require the same level of winterization as inboard and stern drive engines. However, outboard engines may lack the power and torque of inboard and stern drive engines, and they tend to be noisier due to the engine being exposed.

Inboard Engines

Inboard engines are located inside the boat's hull. They are four-stroke automotive engines that have been modified for use on the water. These engines power a drive shaft that is connected to a propeller. Inboard engines do not steer the boat; instead, they use a rudder controlled by a steering wheel. Inboard propulsion systems are popular in watersport boats due to the small, clean wake created by the position of the propeller underwater. They are also easier to repair and service compared to stern drive and outboard engines. However, the engine location can take up space in the centre of the boat, resulting in less seating.

Stern Drive Engines

Stern drive engines, also called "inboard-outboard" engines, combine elements of inboard and outboard systems. The engine is an inboard engine, often a marinized automotive engine, while the boat is driven via a lower unit similar to outboard motors. Stern drive engines can be trimmed like an outboard motor, and they offer more power than outboard motors. The engine is located at the stern, allowing for more seating space and a larger rear platform. However, the lower unit of a stern drive engine is continuously exposed to water, which can cause damage.

Engine horsepower

When choosing an engine for a small boat, there are several factors to consider, including the type of engine, horsepower, weight, and intended use.

Types of Engines

There are three main types of boat engines: outboard, inboard, and stern drive. Outboard engines are mounted on the transom of the boat and are used for both power and steering. Inboard engines, on the other hand, are located inside the boat's hull and power a drive shaft connected to a propeller. Stern drive engines, sometimes called "inboard-outboards," share features of both outboard and inboard engines.

Horsepower is a measure of an engine's power output and is an important consideration when choosing an engine for a small boat. The required horsepower will depend on the size and weight of the boat, as well as the intended use. For example, a small boat like a Jon boat or dinghy may require an engine with 3-10 horsepower, while larger boats, such as medium to large Jon boats, skiffs, and inflatables, may need 20 horsepower or more.

When selecting an engine, it is important to refer to the maximum horsepower specified for your boat, usually found on a metal tag inside the vessel. Choosing an engine with higher horsepower than specified can be dangerous and may cause issues with boat handling and stability.

Weight Considerations

The weight of the engine is also an important factor, especially for small boats. Heavier engines can affect the boat's performance and fuel efficiency. Lighter engines, such as the Suzuki 20 HP outboard, can be a better choice for small boats, as they won't weigh down the craft. Additionally, for lightweight boats like aluminium fishing boats, tenders, and inflatables, a lightweight engine like the Yamaha 20 HP outboard, weighing just 126 pounds, is more suitable.

Electric vs Gas Engines

Another consideration is whether to choose an electric or gas engine. Electric motors offer several advantages, including quiet operation, easy starting, and lower maintenance costs. They are also more environmentally friendly, especially when trolling at slow speeds. However, gas engines may be more affordable upfront and can offer higher horsepower options.

Fuel efficiency

There are several ways to improve the fuel efficiency of a boat engine. Firstly, choosing the right type of engine is important. Two-stroke or low-speed diesel engines are popular choices for small boats as they have low fuel consumption requirements. Electric motors are also an excellent option for small boats as they are portable, lightweight, easy to start, and provide a long runtime. Electric motors are also more environmentally friendly and produce less noise than traditional gas engines.

Another factor that affects fuel efficiency is the type of fuel used. Heavy fuel oil (HFO) is commonly used for larger ships but is not very efficient and leads to increased pollution. More efficient and eco-friendly alternatives include marine gas oil (MGO), liquefied natural gas (LNG), and biofuels. LNG, in particular, offers incredible fuel savings and reduces emissions, corrosion, and wear and tear on engines.

The speed of the vessel also impacts fuel efficiency. Operating a ship at high speed requires more fuel due to increased water pressure. Therefore, travelling at slower speeds can help preserve fuel and increase travel time. Additionally, the ocean and environmental conditions can also affect the speed and fuel consumption of a vessel. Using navigational systems can help shipping companies choose simpler routes, reducing negative outputs and improving fuel efficiency.

Finally, proper maintenance and fuel treatment are crucial for optimizing fuel efficiency. This includes removing impurities from the fuel, ensuring correct fuel temperature and viscosity, maintaining correct air-fuel ratios, and optimizing injection timing, atomization, and compression temperature.

Engine maintenance

Consult the Owner's Manual:

Each small engine model has unique maintenance requirements. Refer to your owner's manual for specific guidelines and maintenance schedules provided by the manufacturer. This will ensure you're performing the correct procedures at the right intervals.

Routine Oil Changes:

Routinely checking and changing the engine oil is vital for engine health. It is generally recommended to perform an oil change after every 50 hours of engine use or at least once a season. Using a product like Sea Foam Motor Treatment during oil changes can help clean harmful residues and deposits, improving oil flow and lubrication.

Fuel System Care:

Keeping the fuel system clean and using fresh fuel is essential. Fuel can break down over time, leading to the formation of sticky varnish that can cause issues. Use fuel stabilizers or additives to prevent oxidation and deposits in the fuel system. Additionally, install a high-quality fuel filter to keep water and debris out of the engine.

Air Filter Maintenance:

The air filter plays a critical role in preventing dirt and debris from entering the engine. Regularly clean or replace the air filter to ensure maximum airflow, which is vital for engine performance and fuel efficiency.

Spark Plug and Battery Maintenance:

Inspect and replace spark plugs regularly to maintain peak engine performance. If your engine uses a battery, keep it and its connections clean and corrosion-free. Check the battery's fluid levels and test its overall health periodically to prevent unexpected failures.

Engine Flushing:

After boating in saltwater, it's crucial to flush your engine to remove any salt buildup. Refer to your owner's manual or seek guidance from a professional technician for instructions on flushing your specific engine type.

Annual Servicing:

Complete annual servicing of your engine, either by yourself or by hiring a professional technician. This basic service includes tasks such as oil and filter changes, changing the gearcase lubricant, and inspecting various components.

Winterizing the Engine:

If you use your boat in colder climates, don't forget to winterize the engine. This process involves flushing the cooling system with antifreeze to prevent freezing and potential damage to the engine. Refer to your owner's manual or seek professional assistance for winterizing procedures.

Visual Inspections:

After each trip, perform a simple visual inspection of all the boat's systems. This allows you to identify any potential issues and decide whether to address them yourself or take the boat in for repairs.

Clean and Lubricate:

Keep your boat clean and well-lubricated where necessary. Wash and wax the hull regularly to prevent oxidation and chalkiness. Lubricate moving parts as needed to ensure smooth operation.

Frequently asked questions