What Is Outdrive On A Boat? | LakeWizard

Key Takeaways

  • Outdrive, also referred to as sterndrive, is the rear bottom section of an inboard engine where the propeller is located.
  • An outdrive engine system generates and carries power from the inboard to the outboard on the boat.
  • Sterndrives are much different from outboards. They are heavier and more expensive to maintain but work well on larger vessels.

One of the great things about boats is the availability of different designs. One of these options is outdrive, but what exactly is it and how does it work?

Outdrive is a propulsion mechanism in boats, also known as a sterndrive engine. Outdrive on a boat generates and carries power from the inboard engine to the outboard. This system is located inside the boat and includes upper and lower units.

From my experiences, I've observed that outdrives (also called sterndrives) combine the best of both inboard and outboard motors, as the engine is located inside the boat, while the propeller or main outdrive unit is submerged outside the hull. Below I’ll explain my findings and explore the intricacies of outdrive boats, their advantages, and the various types that exist in the boating world.

Table of contents


What is Outdrive on a Boat? A Quick Guide to Understanding Its Function

Outdrive is the drive unit on a boat. It’s a type of propulsion system also known as a sterndrive. This functionality carries the power from the inboard engine to the outboard motor.

The outdrive unit includes a propeller, a gearbox, and a system of gears that transfer the power from the engine to the propeller. The outdrive is steerable, allowing the boat to be maneuvered with greater precision than a fixed inboard engine.

The main engine, usually a 4-stroke, is installed inside the boat, specifically underneath the hull. The propeller or main outdrive unit is mounted outside the boat, submerged in the water. It is a crucial propulsion mechanism allowing boats with inboard engines to operate an external drive efficiently.

Outdrives are typically attached to the rear of the vessel and allow for various horsepower and speed capabilities. It will receive power from the upper unit gearbox. In my experience, an outdrive engine can either refer to an outboard engine or a sterndrive engine.

Outdrive is also found on many inboard outboard boats. For clarity, it's essential to note that outdrives are not the same as outboard motors since the latter is an entirely external unit mounted on the boat's transom.

Outboards Vs. Sterndrives Comparison

In my experience, boat enthusiasts often debate the advantages of outboard and sterndrive engines. I've found that both types of motors have their own unique benefits and drawbacks.

So, let me offer you a comparison to help give you a better understanding of each motor type. This table makes the information easier to digest if you’re someone who’s debating between a stern drive engine and an outboard.

Outboard Sterndrive
Weight 155-359 lbs 200-650 lbs
Acceleration & Top Speed 48-51 mph 49-52 mph
Fuel Economy 1.3 to 1.4 mpg 1.3 to 1.6 mpg
Cost $5,500 avg. $9,000-$10,000
Maintenance & Repair Cheaper & easier to maintain More expensive to fix

Outboard engines are usually more compact and lighter than sterndrives, which can affect a boat's overall performance. As a rule of thumb, outboard engines tend to be quieter and offer faster acceleration and higher top speeds.

Typically, smaller boats will have an outboard motor mounted on the exterior to improve space inside the boat too. This is not necessary when using an outdrive motor.

They’re found in the engine compartment area. The outboard is better for small boats because it can counter-rotating propellers.

Sterndrives can be more expensive to maintain and repair. This is the biggest difference between the two types. Most repair shops told us that they specialize in outdrive repairs and focus mostly on preventive maintenance for outboards because they rarely have major issues.

How Do Outdrives Work On a Boat?

During my boating experiences, I've found that understanding how outdrives work can be essential for efficient and safe operation. In this section, I'll discuss the key components and how to operate an outdrive.

Key Outdrive Components

Outdrives combine both inboard and outboard elements, resulting in optimal propulsion for many boat types. The main parts of an outdrive include the engine, drive unit, and vertical driveshaft receiving power.

Stern drives are efficient and provide the appropriate power range most boats need. They are attached through a transom to turn the drive shaft to generate power.

Most outdrive engines are outboards, meaning the drive unit or steering component is outside the boat's hull. Another option is a sterndrive engine (inboard), which has the engine on the boat's stern.

Operating an Outdrive

Operating an outdrive is quite simple when one masters the process. First, it is essential to perform regular maintenance and servicing to ensure the outdrive is in good condition.

This includes retorquing the steering and hinge pins and inspecting various components like bellows, U-joints, and splines.

When starting an outdrive boat, I ensure that the gear shift is neutral to prevent sudden movement. Then, I start the engine and monitor for any signs of malfunction or issues. Once the engine runs smoothly, I am ready to engage the gear shift and navigate through the water.

Is Sterndrive The Same as Outdrive?

The terms "sterndrive" and "outdrive" are often used interchangeably in the boating world. They both refer to a type of marine propulsion system that combines the inboard engine with an outboard drive.

The sterndrive, also known as an inboard/outboard drive, has the engine mounted inside the boat while the drive unit sits outside the hull. This will change depending on the boat type or where you are. For example, Europe diesel engines used in boats differ from those in North America.

As a boat owner, I appreciate the advantages of sterndrives. For example, they provide better fuel efficiency and maneuverability than outboard engines. Additionally, they help maintain the sleek look of my boat, as the engine is neatly hidden inside.

So, when fellow boaters ask me about sterndrives and outdrive, I explain that they're essentially the same thing, and both offer the benefits of inboard and outboard systems in one package.

Maintaining Outdrives On A Boat

As a boat owner, I know how important it is to take care of my boat's outdrive. In this section, I'll discuss routine maintenance and major repairs to keep the outdrive in top shape.

Routine Maintenance

Inspecting the raw water cooling system is crucial for proper outdrive maintenance. I always check the impeller, clean the strainer gauze, and remove salt from the passageways.

It's also a good idea to align and lubricate the gimbal bearing, universal joint, and driveshaft when reinstalling the outdrive. Replacing the zinc anodes is another vital routine maintenance step that should not be overlooked.

Major Repairs

When it comes to major repairs, servicing the gimbal ring and transom assembly is important. As part of this process, I retorque the steering and hinge pins. I also inspect all bellows, U-joints, and splines while lubricating all grease points and replacing worn parts.

This helps prevent serious problems and prolong the life of the outdrive. Beyond this, it is always best to consult a professional for any major repairs or issues regarding the outdrive. They can help diagnose and fix any problems that might be beyond my skill set.


Brian Samson

Brian Samson

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.

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