- The outdrive on a boat is the part of an inboard motor where the propeller is located.
- An inboard motor is placed towards the middle and the outdrive is placed at the stern.
- Compared to an outboard engine, an engine with an outdrive can be easier to control.
If you own a boat, you familiarize yourself with certain parts of a boat’s engine. The outdrive on a boat is a critical part you should know about.
The outdrive on a boat is the rear bottom section of an inboard engine where the propeller is located. Since the outdrive is often located at the stern of a boat, it is also referred to as the sterndrive or outboard drive.
Boat engines come in different shapes and sizes with a wide range of horsepower and speed capabilities. Water vessels have inboard outboard propulsion systems that are often driven with a propeller that spins in the water to move the vessel in various directions.
What Is Outdrive On A Boat?
The Drive Of An Inboard Engine
The outdrive on a boat is typically located towards the bottom rear (or stern) of the boat at a distance from a more centrally-positioned inboard motor.
Without the outdrive, an inboard motor would not have an in-water mechanism that enables the boat to turn or accelerate.
The part of an inboard engine where the motor runs is often placed towards the top middle of the boat.
This type of engine and motor setup is similar to a standard road vehicle where the motor is under the hood and the rotating mechanisms used for acceleration and turning are at the bottom of the vehicle.
On a boat, an inboard motor can generate power through an electric or internal combustion system that is transferred to the outdrive of a boat, which is similar to the way power is transferred from a car’s motor to its wheels.
Sprockets, rubber bellows, and other drive shaft mechanisms in the engine compartment allow the propeller unit to spin in various directions at different speeds.
An engine in a skiff or dinghy will generally have a smaller drive unit that is closely attached to the upper half.
Outboard Drive Vs. Outboard Motors
A boat engine where the outdrive components are part of a singular marine propulsion system is called an outboard engine.
Unlike an inboard motor, outboard motors are contained within the same unit as its drive.
For the most part, an outboard engine is a simple propulsion system commonly used in shallow water.
A sterndrive boat with a separate lower unit and more complex drive shaft allow for more power on larger boats used for water skiing and other higher-speed activities.
Outboard engines are well-suited for smaller water vessels with limited space to attach counter rotating propellers.
Since the bottom half contains the outdrive unit, a smaller vessel doesn’t need more room to house larger components like those on a stern drive engine.
The entire engine is usually attached to the stern where the steering and acceleration are controlled at the same location as the motor.
Unlike an outboard system, the propeller section of an inboard system allows the steering unit to be placed more towards the front (or bow).
This type of steering system can make it easier for the driver to control the boat with a cockpit and helm in front of them.
Is An Inboard Motor Better Than An Outboard Motor?
Sterndrive Boats Vs. Other Boats
Steering and navigation systems with dashboards and wheels are often more user-friendly than a tiller (the control stick) on an outboard engine since inboard controls often have more intuitive designs and functionality.
When controlling the helm of an inboard motor vessel, turning the wheel right will make the vessel turn right and turning the wheel left will make the vessel turn left.
With an outboard system, turning the tiller to the right will make the vessel turn left and turning the tiller to the left will make the vessel turn right.
Inboard Engine Stability
If you don’t mind spending more money, buying a water vessel with an inboard motor might offer greater stability since the motor is more securely placed at the center of your boat with the outdrive balancing the weight out towards the stern.
Unlike heavy outboard motors that can place significant weight on the stern, an inboard motor might have better reinforcement when attached toward the middle.
Since the steering controls for an outboard engine are located at the stern, the person driving must also be situated at the stern.
Sterndrive Engines And Road Vehicles
An inboard motor may have a steering unit that is similar to a common road vehicle like a car, truck, or motorcycle.
The cockpit may have a helm with a wheel like a car or handlebars like a motorbike.
Most of the vessels I’ve captained have had wheels for steering, but handlebars are much more commonplace these days.
Though I like using many types of systems to control a boat, using handlebars to control the outdrive on a boat is easier for me than using a tiller on an outboard system.
The pilot of a boat with an outdrive may have easier access to a traditional dashboard with speed, fuel, and other boat-related information.
Other useful controls may also be in and around the dashboard such as a horn, lighting controls, and communication systems.
Since the outdrive of an engine is often located at the stern (or rear section) of a boat, it is sometimes referred to as a sterndrive.
The sterndrive is simply the part of the water vessel that takes the power from the inboard motor and rapidly spins the water-immersed propeller to move the vessel in whatever direction the captain wants it to go.
The Downsides Of Stern Drives
More Complex Drive Shaft
Though an inboard system on a water vessel may be more user-friendly to operate than an outboard motor, an inboard system may be more complicated to install and maintain.
If you are thinking about buying a new water vessel, you should know that an inboard motor may be more expensive than a vessel with an outboard motor mounted on it.
There are generally more moving pieces and more complex mechanics in an inboard motor, which can make this type of system more difficult and costly to repair.
You may have to repair or replace more parts such as shafts, sprockets, and rubber bellows.
If you're looking for a simple engine system you can attach to a skiff or dinghy, the less expensive and more straightforward option might be to use an outdrive motor.
Other Inboard Outboard Considerations
Controlling a boat from the stern may limit the amount of objects and people that can be placed towards the front and middle.
If there are too many people and objects towards the bow, they could obstruct the view of the person driving.
If you want to have more objects such as tables and other furnishings, it might be more efficient for you to have a vessel with an inboard motor.
A vessel with an inboard motor and outdrive might also allow for more people to be situated towards the front.
You may not have to worry as much about passengers standing up and moving around.
About THE AUTHOR
I have a deep love of houseboating and the life-changing experiences houseboating has brought into my life. I’ve been going to Lake Powell on our family’s houseboat for over 30 years and have made many great memories, first as a child and now as a parent. My family has a passion for helping others have similar fun, safe experiences on their houseboat.Read More About Brian Samson