GUIDE: Which engine to choose for a 5m boat?

GUIDE: Which engine to choose for a 5m boat?

A boat engine is chosen with care. If it is not suitable for your boat, it can in the best of cases tire you (poor performance when towing a buoy, for example). And in the worst, it can put you in danger. For example, an underpowered boat engine will struggle to move forward in strong currents. And conversely, an overpowered outboard motor can damage the structure of your boat. It is therefore crucial to choose the right type of engine with a power adapted to your boat. In this guide, we explain which engine to choose for a 5m boat.

WARNING: This article is a summary in which we provide targeted information concerning the motors for 5 meter boats. But to fully understand how to choose a boat engine, we invite you to read the much more complete article “Which outboard engine to choose for a boat? ". Also we have written other synthetic articles answering the same question but with targeted answers for different boat lengths:

The criteria to know when choosing a boat engine.

There are many options to consider before buying a boat engine. You will have to choose between:

And once you know the answers to all these questions, you will also have to decide:

In the rest of this article, we explain to you point by point which criteria to choose in order to install the most suitable outboard motor for your 5m boat.

Which type of engine is most suitable for your 5m boat?

The gasoline outboard engine is the most common on 5m boats. In addition, the gasoline outboard motor adapts to any what kind of 5m boat : whether it is an open hull, a speedboat, a semi-rigid inflatable boat or a fishing boat.

Finally, its versatility makes it the ideal choice for all types of navigation. It will be suitable for outings at sea as well as on freshwater areas such as lakes or rivers. It will only be enough to adapt the power of the engine to the currents of your navigation area.

Be aware, however, that there is an exception. Indeed, some boat owners prefer to install a semi outboard boat motor.

NB: Electric outboard motors are not recommended for 5m boats. They are generally used for boats of less than 3 meters... Indeed, despite all their advantages (silent, vibration-free, environmentally friendly, light, etc.), electric outboard motors are today still too little powerful to meet the needs of a 5m boat. In addition, electric boat motors are much more expensive and have very limited battery life, which limits boating time.

Under what circumstances is a sterndrive engine recommended for a 5m boat?

5m long boats that do not choose an outboard motor install almost all a semi-outboard engine. We do not recommend this choice because the advantages of the outboard are always greater than the gains generated by the stern drive. The main strength of sterndrives comes from their propeller which is perfectly aligned with the boat. This is due to the combination of an inboard motor and a gear case like on an outboard.

Which outboard motor power to choose for a 5m boat?

A gasoline outboard motor can have a power between 0,5 HP and 450 horsepower! There are 6hp boat motors, 15hp, 25hp, 30hp, 50hp, 60hp, 75hp, 100hp, 150hp, 250hp, etc. Because of this wide choice, many boaters do not choose the power of their outboard motor well. Indeed, there are two categories of buyers. Either the power of the outboard motor is chosen according to the budget and the 5 meter boat is often underpowered. Either the power of the outboard motor is chosen to go as fast as possible and the 5-meter boat is often overpowered.

The best (and only) rule to consider is to choose a outboard motor power equal to or slightly less than the maximum power prescribed by the manufacturer of your boat. Thus, you will be able to face all situations without ever risking damaging the physical integrity of your boat.

The only exception being if you are always maximum two on board or if you use your boat exclusively on a river or a lake. So instead of equaling the maximum power, you can take a boat engine with the power recommended by the manufacturer (and save money on the purchase!).

Most outboard motor brands recommend a minimum power of 70hp for a 5m boat (recommended power). Nevertheless, we recommend that you get closer to the maximum recommended power. For a 5m boat, the maximum engine power is 150hp.

A good compromise for your budget, used by many boaters, is to choose a 110hp outboard motor on a 5m boat. (for a vessel weight of 500 kg empty and 900 kg laden)

However, these indications may vary depending on your type of boat (sailboat, yacht, zodiac, etc.), the weight of the boat and the currents in your navigation area. It is therefore necessary to inquire with the manufacturer or with a local marine mechanic.

2-stroke direct injection engine or 4-stroke outboard motor for a 5m boat?

Today there are modern 2-stroke engines known as direct injection (DFI). This DFI technology allows two-stroke boat engines to no longer waste gasoline that has not exploded. As a result, these 'new' two-stroke engines for boats only have advantages.

They are the simplest, lightest, cheapest, most powerful, least polluting, most fuel efficient and best performing outboard motors on the market today! We therefore recommend without hesitation a direct injection 2-stroke gasoline outboard engine for a 5m boat. 

What shaft length to choose for the outboard motor of a 5m boat?

Not all 5m boats are alike so they won't need the same shaft length. Depending on the architecture of your boat, you will need more or less shaft length so that the propeller is submerged to the right depth. To know what shaft length to choose for your 5m boat, just measure the height of the transom:

  • Short shaft boat motor = 38cm transom height.
  • Long shaft boat motor = 51cm transom height.

Which motor propeller to choose for your 5m boat?

The propeller is chosen according to the speed of your engine and not the length of the boat. When the boat reaches its maximum speed, the engine must be at full speed (between 5000 and 6000 rpm depending on the model). Otherwise, the outboard motor is damaged either by pushing it too hard or because it is overspeeding. So a 5 meter launch will not need the same propeller as a 5 meter sailboat.

NB: Cupped propellers are not recommended if you do not plan to sail at more than 30 knots.

Choosing the diameter and number of blades of an engine propeller

As a general rule, to get the best performance out of your boat engine, you need a large diameter propeller and as few blades as possible. But the more powerful your engine, the more propeller area (and therefore blades or diameter) will be needed to avoid cavitation problems. In practice, it is therefore recommended to choose a three-blade propeller for your 5m boat.

The choice of propeller pitch on a 5m boat

Choosing a propeller with the right pitch is crucial because it determines the acceleration, the maximum speed and the fuel consumption of the boat. But what is propeller pitch? This is the distance traveled by the propeller on each revolution. Propeller pitch is very often expressed in inches.

If we take the analogy of a car:

  • A small step is like first gear. In the car, it is used to climb hills and to accelerate. On a boat, we use a small step when we are very loaded or when we are water skiing.
  • A medium pitch is like third gear. It's versatile in the city for cars and on the sea this is the recommended propeller pitch for 5m boats.
  • A big step is like sixth gear. The boat's engine becomes quieter and consumes less. This is ideal when maintaining cruising speed for a long time. 

What is the best engine brand for a 5m boat?

There is no classification of best engine brands for 5m boats. Quite simply because all the big brands are equal. They all offer excellent engines and warranties of at least 3 years.

  • For two-stroke outboard motors, the brands Evinrude, Mercury, Selva, Tohatsu, Nissan and Yamaha. 
  • For semi-outboard motors, the brands Ilmor, Mercruiser and Volvo Penta are references.

However, for a 5m boat, we recommend Mercury two-stroke gasoline outboards. They have a 5-year warranty and are the most common. Their popularity is a strength because they not only have a very wide range but above all an after-sales service accessible almost anywhere in the world.

Indeed, as all established brands are the same, the number one criterion for choosing a boat engine is the ease of engine maintenance and quick access to spare parts. 

Conclusion: which engine to choose for a 5m boat?

Below is the summary of this article that answers the question: which engine to choose for a 5m boat?

For a 5m boat, we recommend a Mercury two-stroke direct injection (DFI) gasoline outboard engine, rated close to the maximum power recommended (usually 150hp) by the manufacturer.

Choose a short shaft outboard if your transom height is 38cm and a long shaft if it is 51cm.

Next, you need to choose a medium-pitch three-blade propeller.

NB: It is absolutely necessary to respect the maximum weight of the motor indicated by the manufacturer of your boat.

Finally, if you are looking for cheap boat motors, you can look for used outboard motors on sites like ebay. There are some real good deals from time to time! But it will absolutely be necessary to ask for the report of an independent marine mechanic to be sure that it is in good condition.

CAUTION: This conclusion is a summary that communicates general information on outboard motors suitable for 5m boats. Read the entire article to understand all the nuances that may apply to your boat. Your boat may not be 'average'. You will then have to refer you to a professional who will be able to provide you with tailor-made advice. 

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