What are the differences between an inboard and outboard boat?

Darren Richman July 30, 2018

Potential boat buyers wanting to know the difference between inboard and outboard boat may hear.  Inboard boats are the only way to go or I would only buy an outboard.  First time buyers may ask, what is the difference between an inboard and an outboard boat?  Does it really matter what I get?

Yes, it does matter and there are several choices between inboard and outboard motor types. The differences are actually significant, especially if you have a specific use in mind for your new boat.

The terms come from motor placement in the boat and how the boat is propelled through the water.  This article will only consider trailer boats of 25 feet or less in length.  I will look at the differences, advantages, disadvantages and recommendations for intended use.

Inboard Boats

Inboard boats come primarily in two flavors, direct drive and v-drive configurations.  Direct drive boats have the motor midship with a drive shaft exiting the motor to the rear of the boat.  While V-drive boats have the motor in the back of the boat.  The v-drive output shaft goes forward into a simple gear box that redirects the drive shaft to the rear of the boat. There is a simple transmission between the motor and drive shaft of both inboards to offer forward, nuetral and reverse options.  The drive shaft then exits through the bottom of the boat.  At this point under the boat the propeller is connected to the drive shaft. After the propeller there is a rudder attached to the bottom at the very rear of the boat.  Inboard boats in this size range are typically powered by a V8 gasoline engine.

Inboard Advantages

  • Simple drive train, so fewer potential problems than an outboard or inboard/outboard (stern drive) boat.
  • Great handling on plane and quick performance characteristics.  These boats get on plane very quickly and corner precisely.
  • Propeller is located below the boat in front of the transom, keeping it safely out of area for swimmers and watersports.
  • Great wake for skiing, wakeboarding, surfing (v-drive) and other water sports activities.
  • Lots of onboard storage and room for passengers in the v-drive configuration.
  • Easy boarding from the water as swim platform sits right at the water level

Inboard Disadvantages

  • No directional control when boat is in reverse.  With the rudder in back of the propeller, there is no ability to change directions in reverse.
  • A fixed propeller and rudder means that shallow water is an enemy to an inboard.  Running these boats in shallow water could cost you a new propeller or worse.
  • A fixed propeller also means no ability to trim the boat for maximum cruising fuel efficiency.
  • Very little onboard storage in the direct drive configuration.

Intended Uses

  • Waterskiing
  • Wake boarding
  • Wake surfing and all other water sports

Outboard Boats

Outboard boats have the entire motor, outdrive and propeller mounted behind the transom or rear of the boat.  These all in one units are basically bolted to a mounting plate on the rear of the boat.  These motors generally are four cylinder motors up to v-8 motors.  In a 18 to 25 foot boat the horsepower ratings can range anywhere from 60 to 350 horsepower.

Outboard Advantages

  • Good low speed control in forward and reverse.
  • Generally more fuel efficient than other similar horsepower motor/outdrive configurations.
  • Able to raise the propeller in shallow water.
  • Able to install a jet drive kit on many outboards to allow shallow water operation.
  • In the right hull, can be a good option for skiing or barefooting.

Outboard Disadvantages

  • Outboard motor is mounted to transom so you cannot have a full swim platform.
  • More dangerous for swimmers and watersports due to propeller openly exposed at the rear of transom.
  • Not suitable for wakeboarding and definitely out for surfing due to lack of wake and dangerous propeller location.

Intended Uses

  • Fishing boats – especially tournament bass boats
  • Cruising the lake in a runabout boat
  • A less expensive way to enjoy boating with some of the lower horsepower models.

Configurations in between an Inboard and Outboard

There are two popular configurations for trailer boats in the 18 to 25 foot range that fall in between inboards and outboards.  Stern drives, also known as inboard / outboards or in / outs, as well as jet drives are popular configurations.  Each filling specific needs for the potential boat buyer.

Stern Drives

Stern drive boats are a very popular configuration for this size boat.  The motor is located near the back of the boat.  The driveshaft goes from the motor and through the transom into and outdrive.  An outdrive is attached to the rear of the boat that sends the power of the engine down to the propeller.  The outdrive is capable of raising the propeller out of the water for trailering and shallow water conditions.  These boats are also fully trimmable while running to increase fuel efficiency and optimal running attitude on the water.  Stern drives in the 18 to 25 foot range could have a four cylinder, six, or v-8 engine.

Advantages

  • Good low speed control
  • A boat that is good for multiple watersports
  • Lots of storage room and room for passengers
  • Ability to trim for better efficiency and optimal running attitude
  • Wide variety of engine choices for your specific needs
  • Ability to have a full swim platform in the rear of the boat

Disadvantages

  • More complicated and potentially expensive drive train than other options
  • Good for many watersports, great at none due to safety and washed out wake
  • Heavy motor and outdrive in the rear of the boat equals slower to plane and more bow rise.

Intended Uses

  • Cruising the lake quietly and efficiently
  • Pulling a variety of water sports
  • For those that care more about ease of operation than quality of the wake

Jet Drive

Jet drive configurations often have the motor near the rear of the boat.  The drive shaft connects the motor to an impeller.  Water is pulled into a pump from an intake in the bottom of the boat and shot out the rear of the boat through a nozzle.  Jet drives come in different motor configurations and hull materials.  There are the traditional fiberglass hulls with either a single or double engine configuration.  There are also aluminum hull jet boats with generally one engine in this size, but occasionally may be found with 2 engines in boats around 25 feet in length.  Jet boats are growing in popularity due to being versatile, safe for swimmers, and relatively simple power train.

Advantages

  • Ability to run in shallow water
  • Can tow all the different water sports activities safely
  • Safe for swimmers
  • Good handling on plane (can have good low speed handling depending on the jet drive system)
  • Abundant storage

Disadvantages

  • Perhaps the least fuel efficient drive system mentioned in this article
  • Although safe for water sports, wake is often washed out and not clean like an inboard or v-drive
  • Low speed handling can be poor in some depending on the jet drive system, test drive to see if the boat you are looking at is poor or good.
  • Loud exhaust (this can be bad for some, music to the ears of others)

Intended Use

  • Fishing
  • Safely pulling a variety of water sports
  • A must have in the aluminum hull version for navigating swift or shallow rivers

Conclusion

There really is the right boat for you out there it just matters what you want your boat to do and where it will be used.  Modern boats are also well made and very reliable when maintained properly.  So, determine what matters to you and go find your boat.  Then, go enjoy your time on the water.