How to Mount an Outboard Motor Properly

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The best way to add an extra boost to any small boat is by installing an outboard motor. The process may seem simple for experienced boat riders but can be challenging for beginners, and each outboard motor may require a different installation method. 

 

Replacing an outboard motor will also give you a good opportunity to clean and repair parts of the boat that are hard to reach while installing the motor. 

 

Read along to learn more about how to mount an outboard motor properly.

 

 

Outboard Motor Installation

 

Whether you’re mounting an outboard motor on aluminum boats or not, It’s important to always check the owner’s manual for every new outboard motor because the installation process can vary significantly between brands and models. Knowing your boat’s transom height will be essential to figure out what size your new outboard motor should be. 

 

The transom is the vertical section at the back of the boat where outboard motors are mounted. Let’s take a closer look at our outboard installation guide to determine how to install outboard motors.

 

 

Parts of an Outboard Motor

 

Before you learn how to mount an outboard motor properly, you need to know the various parts. You may need to look at a boat motor parts diagram to visualize this.

 

 

• Engine – the highest part of the outboard engine which powers it.
• Tiller – steers the boat by manually adjusting the engine’s direction.
• Mounting bracket – attaches to the boat’s transom and mounts the outboard engine.
• Anti-ventilation plate – prevents propeller blades from sucking surface air.
• Water intake port – keeps the engine cool by sucking water. 
• Propeller – creates the necessary force to move the boat. 
• Skeg – protects the propeller and allows you to steer safely and precisely. 

 

 

Tools and Supplies

 

To install an outboard motor, you will need a drill, some marine sealant or adhesive, and a good set of wrenches. Use stainless steel bolts, washers, and locknuts to mount the engine on the transom and figure out measurements using a pencil, tape measure, and tape. 

 

 

Outboard Motor Size

 

Installing an outboard motor that fits properly with your vessel will require you to know the right measurements of some components. Start by measuring your boat’s transom, from top to bottom, and your outboard motor’s shaft length, which goes from the anti-ventilation plate to the bottom of the engine head. 

 

 

The outboard motor will be properly-sized when the transom height matches the outboard motor’s shaft length. It helps to look at an outboard motor height diagram to determine this.

 

 

Mount Your Outboard Motor

 

Use the mounting bracket to attach the outboard motor at the center of the boat’s transom by tightening the bracket screws. 

 

 

Adjust the Motor Angles

 

Most outboard motors will work fine with a motor shaft angled parallel to the boat’s transom, but always check the owner’s manual for specific instructions and suggestions. The boat’s stability will highly depend on how the motor angle is adjusted. 

 

 

Boats that have their motor angled too far tend to shoot upwards while cruising, while those with motors angled too close will plunge towards the water more often.  

 

 

Position the Fuel Tank

 

The fuel tank will connect to the outboard motor using the fuel hose. It’s very important that the fuel tank doesn’t move around while using the boat, so it should be securely placed in a well-ventilated area and away from direct sunlight. 

 

You can keep it as far as 6 feet away from the outboard motor and 3 feet below the fuel connector. 

 

 

How to Understand if the Motor is Not Properly Mounted

 

An outboard motor that is not mounted properly can have negative effects on the boat’s performance, and it is very critical to install them at the right height. The most common way of mounting an outboard motor is by making sure that the anti-ventilation plate is aligned with the bottom of the boat, where the motor is neither too high nor too low. 

 

If your outboard motor is mounted correctly, the anti-ventilation plate should skid on the water surface while cruising.

 

A good way to test if your outboard motor is mounted at a proper height will require you to trim the motor, which means moving the motor closer to or farther from the boat. 

 

While keeping the engine idle, trim the motor out between a half and almost full trim, and accelerate at a rapid pace with caution. The propeller will not ventilate during this test if the engine is set too low, indicating that it should be raised. If the propeller ventilates constantly, it is probably too high and should be lowered. 

 

There are recommended industry standards for mounting an outboard motor properly, but experienced boaters might choose to experiment with different methods. Mounting holes and brackets are aligned vertically on the outboard motor, which allows boaters to adjust their height. The separation between each mounting hole will be 0.75 inches.   

 

 

Too Low

 

Outboard motors that are mounted too low will be mostly submerged underwater and can create an excessive drag, which makes the boat go slower and less fuel-efficient. Propeller pitch, the distance that a propeller moves during each revolution, is also reduced. 

 

Handling your boat might also be more challenging with an outboard motor that’s mounted too low, causing the boat to bounce up and down at regular speeds. 

 

Fishing boats and workboats with heavy cargo that usually move at low speeds tend to run efficiently with motors that are mounted low. 

 

 

Too High

 

Boaters that are looking for speed could benefit from an outboard motor that is mounted high, but there can also be some disadvantages. In this case, the anti-ventilation plate remains above the boat’s bottom.

 

Raising the engine height can make the boat faster while improving its fuel efficiency and propeller pitch. There will also be less drag since only a part of the motor will be touching the water. Setting it too high can prevent the propellers from reaching the water as needed for the outboard motor to function properly. 

 

The engine could overheat if water doesn’t reach it and keep it cool. Boats with motors that are mounted high may also be harder to steer.

 

 

Wrap Up

 

Outboard motors come in four different sizes, which are short (15 inches), long (20 inches), XL (25 inches), and XXL (30 inches). Installation methods will vary between different combinations of outboard motors and boats, and you should understand the importance of their measurements early in the process. 

 

It is recommended for beginners to stick to the industry standard for the outboard motor height, while those who work transporting heavy cargo may prefer a lower motor, and those who race in competitions may want it raised. 

 

Always make sure to mount your outboard motor tight and securely, and remember that the ideal motor height will depend on your individual boating needs.