Boat motor: outboard, sterndrive, diesel, gasoline, water jet? Advantages and disadvantages
In fact, choosing a new motor is not as difficult. There is a simple rule: to get the boat on planning, you need 1 hp for 11 kg of loaded boat weight. And then what? Nuances. Which? We tell in our article.
Gasoline, diesel or gas?
Let’s start with fuel type. Engines that run on gasoline are more compact, quieter, less vibrating & lighter when compared to diesel of the same power. Still, the consumption of gasoline is much higher than that of D. By the way, refuelling a gasoline engine with fuel with an octane rating higher than recommended does not make much sense. Power will not increase, which cannot be said about the amount in the check.
Diesels are less flammable. Subject to the maintenance regulations, they can serve many times longer than gasoline ones. By the way, in the rental boats you can often find diesel-engines. The disadvantages of a diesel engine are weight, dimensions.
Propane, aka liquefied gas. More environmentally friendly and quieter than gasoline engines. But more expensive – difficult to maintain. Finding a specialist will not be easy.
Electric. Today, their middle-maximum power is 80 hp, the cruising range is 50 miles. Such boats are usually found inside megayachts, are used as a water taxi.
Sterndrive or outboard motor?
In general, the larger and more seaworthy the boat, the more modern, expensive the engine should be. Let’s start with outboard motors. Two-stroke engines are easier to maintain, lighter. Four-stroke ones are more modern, more complex, heavier, more expensive, but they work quieter, the consumption is less. The draft of the boat depends on the length of the engine leg. The size is selected depending on the height of the transom.
The sterndrive is the evolution of the OM. Pros. They are be cheaper, easier to repair, easy to remove and take up no space below deck. Benefits of tilt-and-turn motors: more powerful, consume less fuel (diesel), improve handling (twin propeller), more comfortable during planning (low center of gravity), more durable, rarely steal (difficult to remove), suitable for marine areas.
Advantages of an outboard-motor
- Are more economical than stationary & tilt-and-turn columns;
- Installation–replacement is easier, which makes it easier to maintain the engine;
- Since they mounted outside the boat, it maximizes the interior space of the aft area and the swimming platform. Many yachtsmen find this spacious format much more comfortable for relaxation;
- Provide better maneuverability at low speeds, as they have a smaller turning radius compared to stationary motors or tilt-and-turn columns;
- When traveling in shallow water, it is possible to lift the engine out of the water, avoid damage to the propellers;
- If the boat is equipped with a drive with front propellers, it can still be used for wakesurfing.
Disadvantages of an outboard motor
- As a rule, they are louder than stationary ones.
- The power of one is sometimes not enough, so owners install several. However, this solution increases the level of noise, exhaust gases.
- Due to their location, the propellers are more prone to cavitation, the formation of air bubbles around the blades, which reduces the efficiency of the propeller at speed.
- The easiest way to control it – is with a tiller attached directly to the motor. Still, this requires the skipper to be in the stern of the vessel, which is not always convenient. Alternatively, hydraulic or cable systems can be used to allow the navigator to steer the boat from another location. However, this option does not provide the same level of precision as the tiller.
Water jet
If you’re going to be sailing in challenging shallow waters with rocky bottoms or floating debris, then the obvious choice is a water jet. The advantage is the absence of a screw. You may have noticed how the rescue equipment swims as close as possible to a person, while not jamming the water cannon, since it is safe at almost any distance. Also, jet ski are very maneuverable. Remember how they ride jet skis. For an emergency stop, the jet can be rotated 180 degrees. But if you do such a trick with a screw motor, then most likely the end of the drive shaft will come due to the high load.
Do water jets break? Certainly! A fine grate allows sand and small pebbles to pass through, from which the impellers fail. Disadvantages of water cannons: they are more expensive than propeller engines, consume more fuel.