Inboard vs. Outboard Motors: What You Need to Know

Written by Carolyn Jackson


If buying a boat is on your radar, one question you will need to answer is the type of engine you want. Boats are almost always sold without the engine. This is good and bad. It means you need to budget above the MSRP of the boat and plan to pay more for an engine (or two). It also means you have some room for customization and can choose exactly which engine you want. 


When selecting an engine, there is one important choice you need to make first: inboard or outboard? The difference is actually within the words; an inboard engine sits within the structure of the boat and is not visible whereas the outboard engine sits outside the structure of the boat and is clearly visible at all times. 


In this article, we are going to discuss more about what inboard and outboard engines are, the pros and cons of each type of engine, and how much they cost on average. 


If you are not quite ready to talk about engines but are interested in learning more about boating and what types of boats are out there, take a look at our Guide to Buying a Boat and when you’re ready to buy a boat, check out our guide to how much a boat costs


What is an Inboard Motor?

An inboard engine, sometimes referred to as an inboard motor or as sterndrive, is a boat propulsion mechanism that sits inside the hull of the boat permanently. The inboard engine is connected to a driveshaft, which controls the direction of the propeller, steering the boat. 


True Inboard vs I/O 

There is a distinction between a true inboard engine and an inboard/outboard engine we need to discuss. A true inboard is fully inside a boat and an I/O has components within and outside of the boat. A true inboard is less common. True inboard motors will be found on boats designed for skiing as they produce less wake and drive much smoother. I/O engines are more practical for families or boats that want more flexibility. 


True Inboard

When a boat has a true inboard engine, the engine will be placed in the center of the boat (inside the boat) and have a driveshaft connected to a propeller, which will give the boat power. The propeller does not steer the boat. Instead, there is a separate rudder, which controls the steering. In a true inboard, the propeller is in a fixed position and cannot go up or down. 


I/O, Inboard Outboard, Sterndrive

For a boat with an I/O engine, the engine will be placed towards the back of the boat (still fully concealed), but the propeller part of the engine will stick out. An I/O engine is considered a mix of an inboard and an outboard because the engine is inside, but the propeller/rudder is outside. This type of engine is advantageous because the propeller actually steers the boat itself and you can lift it up to avoid shallow water or obstacles. 


What is an Outboard Motor?

An outboard engine is a boat propulsion system that delivers power to a boat via an engine mounted on the outside hull of a boat. They can be operated by hand in smaller boats or connected to a steering and power system (similar to the look and feel of a car) in larger boats. 


Outboard engines can be fully removed from the boat for storage or lifted up so they do not touch the water. This is a nice feature if you want to remove the engine from saltwater to decrease erosion or if you need to avoid obstacles in shallow waters. It can also help with winterizing a boat. 


The outboard engine steers the boat itself by moving left or right. This means the entire engine unit moves and acts as a rudder. 


Outboard motors are more common in boating because they are slightly less expensive, allow more flexibility, more seating capacity, and are easier to maintain. One downside to an outboard engine is that they are loud and create larger wakes, which can be problematic if you use your boat for watersports like skiing. 


What is the Difference Between Inboard and Outboard Motors?

The main difference between an inboard and an outboard engine is their placement in the boat. An inboard is hidden within the boat and an outboard is 100% visible. 


inboard vs outboard motor comparison

The boat on the left has an inboard or sterndrive motor and the boat on the right has an outboard motor.


When you initially purchase your boat you will have to select and purchase an engine as well. Some boats can house either an I/O engine or an outboard engine, but not all boats are equipped for both. Consult with your boat dealer to determine what your options are. 


If either option is available, see if you can test drive a boat with each type of engine. At the end of the day, both engines are great choices and it will come down to your personal preference. The feel when driving with either type of engine is pretty different, so that might persuade you one way or the other. 


Pros and Cons of Inboard and Outboards





What Boats Usually Have an Inboard Engine?

Typically you will see an inboard engine on bowriders, ski boats, and midsize to larger cruiser boats. These types of boats are well-suited for inboard engines because they are large enough to still seat quite a few people, even with the engine living inside the boat. They also cater perfectly to people who want a perfect swimming platform or those who like to ski and enjoy other watersports. 


Almost any boat can have an inboard or I/O engine, but seeing an inboard on certain types of boats is pretty rare, such as bass boats or pontoons


What Boats Usually Have an Outboard Engine?

More boats have outboard engines than inboard, especially for their ease of use and low maintenance cost. You will see outboard engines on pontoons, aluminum boats, bass boats, bowriders, small cruisers, and some high-performance off-shore speed and fishing boats


Boats that are for recreational cruising or fishing are most likely to have outboard motors because the benefits are more advantageous in this setting. Want to learn more about pontoons? Check out our pontoon 101 here


How Much Does an Inboard Motor Cost?

Inboard engines can cost anywhere from $8,000 all the way up to $25,000 and potentially above. For example, on a boat builder of a popular bowrider brand, with an inboard motor, the cost fluctuated by almost $20K just by changing the engine. The lowest cost engine and the highest cost engine for the same boat changed the total MSRP for that boat by over $50K.


Some popular inboard engine brands include: 

  • Aquamot
  • Beta Marine
  • BUKH
  • Mercury Mercruiser
  • Scania
  • Volvo


If you are wondering about how to afford your new boat, take a look at our Guide to Financing a Boat to find tips, tricks, and insight on how financing works in the marine industry. 


How Much Do Outboard Motors Cost?

Outboard engines can cost anywhere from $1,000 to about $15,000+ to purchase upfront. 


Some popular outboard engine brands include:

  • Suzuki
  • Mercury
  • Honda
  • Yamaha
  • Torqeedo
  • Evinrude


To find out more about how much a boat costs in general, take a look at our article on How Much a Boat Costs. 



When selecting a new boat, one decision you will need to make is about the engine. Some boats allow you to customize the engine and with others, you will likely need to go with the manufacturer’s recommendation. For outboard engines, you will need to budget for buying one or more engines in addition to the cost of the boat. For I/O and inboard engines, the cost of the engine is baked into the total MSRP when buying a boat. 


Your boat dealer and manufacturer should be able to help you make an informed decision along with some online research of pros and cons (like here), reviews, and asking around. And don’t forget the most important thing – enjoy life on the water. 


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