Marine Boats, Motors, Inboards, Outboards, Watercraft Service Repair Manuals

Inboard/Outboard Outdrive Sterndrive Jet Drive Service Manuals

Do-it-Yourself Service and Repair Manuals for Inboard Outdrives

There are 4 Types of Inboard Boat Motor Drive Systems

Inboard and Outdrive Manufacturer Brands

Inboard/Outboard, (I/O) Sterndrive, Outdrive

Inboard/Outboard Drive Propulsion SystemThe engine is mounted inside the boat. The transmission/drive unit is outside of the boat, attached to the transom. The engine and drive unit are joined by a torque coupler and universal joint. Moving the drive unit steers the boat.

Inboard/Outboard (I/O) engines otherwise known as Sterndrive combines inboard power with outboard driveability. The engine’s drive unit lies just below the swim deck with the motor mounted under the transom. Sterndrives are mostly used in “pocket cruisers” aka, boats less than 30 feet long that have amenities like a head, galley, and sleeping quarters.

The advantages of a sterndrive over an outboard engine are sterndrives have more horsepower and allow for a more attractive transom as the engine is hidden beneath the boat. They are also easier to fish on.

The advantages a sterndrive has over an inboard are sterndrives have no need for a prop shaft or rudder system making it easy to trailer and operate in shallow water. Sterndrives also allow for more space in the interior passenger cabin of the boat as the engine is mounted all the way in the back of the boat.

Direct-Drive (D-Drive) Inboard Systems

Inboard Direct Drive Propulsion SystemsWith Direct Drive (D-Drive) motors, the engine is mounted in the center of the boat with the prop and rudder built into the hull (underneath the boat). A drive shaft is connected at the rear of the transmission and is run out of the hull through a sealing unit. The propeller is connected directly to the drive shaft outside the hull. A rudder steers the boat.

Direct Drives are used specifically for ski boats as they leave very little wake.

V-Drive Inboard Systems

Inboard V-Drive Propulsion SystemsV-Drive motors are stowed under the transom seating, with a Prop and Rudder built into the hull (underneath the boat). With the use of a universal joint on the end of the transmission, the drive shaft is directed stern-wards under the engine and through the hull. The propeller/rudder arrangement is the same as in a standard inboard installation.

V-Drive Inboard engines are most commonly found on watersport boats making it easy to wakeboard, wakesurf, tube, kneeboard, and anything else you want to try behind the boat, including skiing.

To make larger wakes for wakeboarding, tubing, and wakesurfing, inboard boat manufacturers use built in Ballast Sytems, Surf Systems and unique hull designs to manipulate the wake. To scale back the wake to allow skiing, boaters often choose a “Crossover” model V-Drive inboard boat, like the MasterCraft XT Series for example, designed with a hull that can produce very little wake when the added ballast and surf systems aren’t in use.

Jet Drive Inboard Systems

Inboard Jet Drive Propulsion SystemsLess common than all other configurations, a jet drive consists of an engine mounted inside the boat that is attached to a high speed pump which draws in water through an intake grate, increases its velocity, and forces it out through a directionally adjustable nozzle which is mounted outside the boat.

Changing the direction of this nozzle steers the boat.

Jet drives have a distinct advantage of being able to operate in more shallow water than other inboard drive systems.


Volvo Penta Outdrives


SEI Outdrives

SEI's outdrives are assembled at their factory in Clearwater, Florida. SEI has been in the stern drive business since 2003. SEI Sterndrive Engineering is the largest supplier of replacement outdrives in the world.