An outboard is a self-contained engine, gearcase and propeller that clamps or bolts to the boat’s transom and tilts up out of the water. An inboard engine sits inside the hull and turns a propeller through a shaft under the boat, with a rudder for steering. Outboards are easier to service, replace and keep out of the water, and free up interior space; inboards keep weight low and centered, and are the usual choice for wake and ski boats, larger cruisers and many workboats.
Inboard vs outboard at a glance
| Outboard | Inboard | |
|---|---|---|
| Where the engine is | On the transom, outside the hull | Inside the hull |
| Steering | The whole motor turns | A rudder behind the propeller |
| Shallow water | Tilts up to clear the bottom and for trailering | Shaft, prop and rudder stay below the hull |
| Maintenance access | Easy; the motor can be removed for major work | Engine bay access, often tighter |
| Interior space | More usable deck space | Engine box or compartment takes space |
| Typical boats | Fishing boats, jon boats, pontoons, center consoles, small tenders | Wake and ski boats, cruisers, trawlers, workboats |
Outboard pros and cons
- Pros: simple to maintain and winterize, tilts out of the water to limit corrosion and growth, can be replaced or repowered without major surgery, and frees up the boat’s interior.
- Cons: hangs off the stern, adds weight right at the back, and larger outboards can be noisier at the helm.
Inboard pros and cons
- Pros: weight is low and central for a stable ride, the engine is out of sight, and on wake and ski boats the propeller sits under the hull rather than behind the transom.
- Cons: takes up interior space, the running gear stays in the water, and shaft parts such as the cutless bearing and shaft seal need periodic attention.
What about sterndrives?
A sterndrive, also called an inboard/outboard or I/O, puts the engine inside the hull and drives an outdrive mounted on the transom that steers and tilts like an outboard’s lower unit. It combines an inboard engine with outboard-style steering and trim.
Which should you choose?
- Fishing, shallow water and trailering: an outboard is usually the simpler choice.
- Towing wakeboarders and skiers: boats built for it typically use inboards.
- Repowering: stay with what the hull was designed for; transoms are built for outboard loads, and inboard hulls are laid out around their engine and shaft.
Parts we carry for both
For outboard boats we carry new four-stroke Suzuki, Tohatsu and Mercury outboards from 2.5 to 30 HP; browse outboard motors by horsepower or portable outboard motors, and check the shaft length guide. For inboard boats we carry Michigan Wheel inboard propellers, a cutless shaft bearing and the PropSmith prop puller on our boat propellers page; 3 blade vs 4 blade prop explains blade count.
More guides: what size outboard do I need?.
Shipping is a flat $80.00 per order to US addresses, with 15-day free returns. Questions? Ask a parts specialist.