Bowriders, deck boats and small cruisers are often sold with a choice of power: an engine inside the hull, or an outboard bolted to the transom. Under about 20 feet the choice mostly makes itself, because jon boats, skiffs, inflatables, tenders and most aluminum fishing boats are only built for an outboard. Above that, both are on the table, and the right answer depends on how you use the boat, who does the maintenance and what you want the stern to look like.
What each one is
An inboard puts an automotive-style engine inside the hull. In a direct-drive layout the engine sits amidships and turns a fixed shaft and propeller, with a rudder for steering. In a sterndrive (I/O) the engine sits at the back of the boat and drives an outdrive through the transom, which steers and tilts like the lower half of an outboard.
An outboard is a complete, purpose-built marine engine (powerhead, gearcase and propeller in one unit) that hangs on the transom. They run from 2.5 hp portables you can carry in one hand to 300 hp and 350 hp V6 engines, and in recent years boats that were traditionally inboard powered have moved to single and twin outboards as the engines have grown lighter and more powerful.
Where the outboard wins
- Access. Lift the cowling and the oil, filter, spark plugs, fuel filter and thermostat are all in front of you; the 20, 100 and 200-hour services on a Suzuki are an afternoon with basic tools. The water pump impeller is in the lower unit, which comes off with a few bolts. An inboard engine sits under a hatch, and anything on its far side is a reach.
- It tilts out of the water. Trim up to cross a sandbar, beach the boat or trailer it, and tilt up at the dock so the gearcase and anodes are not sitting in salt water between trips. Stored upright, the cooling passages drain on their own.
- Repowering is a bolt-on job. When the engine reaches the end of its life you unbolt it and mount a new one; the boat itself stays as it was (see rebuild or repower). Replacing an inboard means pulling the engine (and on a sterndrive, the outdrive and transom assembly) out of the hull.
- Weight and space. With no engine box in the cockpit you get more floor, storage and seating for the same length of hull, and the boat is usually lighter for the same horsepower.
- Winter storage is simpler. Change the oil, stabilize the fuel per the owner's manual, flush and let it drain; our outboard storage guide covers the routine. A sterndrive has block drains, a raw-water side and a bellows to look after.
Where the inboard wins
- A clean transom. Because the engine is inside, the stern is free for a full-width swim platform, a boarding ladder and a sun pad over the engine hatch. That is the trade: you give up interior volume to the engine and get the transom back.
- Noise and vibration at the helm. An engine under a hatch behind sound insulation is usually quieter at the driver's seat than an engine hanging in the open air behind you.
- Wake sports. Surfing behind a boat needs the propeller tucked under the hull and away from the rider. That is what inboard ski and forward-drive boats are built for; an outboard, with its propeller at the transom, is not a surf boat.
Cost: purchase, upkeep and resale
Comparing sticker prices by horsepower is misleading, because an outboard is lighter and mounted behind the boat rather than inside it, so a smaller outboard often performs like a larger sterndrive on the same hull. Outboard-powered versions of a given model generally list higher, but ownership usually favors the outboard: routine service is quicker and more of it is do-it-yourself, winterization is simpler, and a boat that can be repowered with a bolt-on engine holds its value better and is easier to sell.
The price of the outboard itself comes down to horsepower, brand, and features such as electric start, power tilt, fuel injection and the length of the factory warranty.
Which one should you choose?
If you want the lowest upkeep, the most usable space, shallow-water access and an easy repower ten years from now, choose the outboard. If you want a clean swim platform, a quieter cockpit or a boat for wake surfing, choose the inboard. For anything small enough to trailer behind a car, a tender, or a fishing boat that gets beached, the outboard is the only realistic option anyway.
If you are going outboard
We are an authorized Suzuki, Honda and Yamaha dealer and stock portable outboards up to 30 hp, shipped free to the lower 48. Before you order, work out the horsepower your hull is rated for and measure your transom so the shaft length is right:
- What size outboard do I need for my boat?
- How to measure for outboard shaft length
- Which battery for a 9.9, 15 or 20 hp electric-start outboard
- How to break in a new Suzuki outboard
Browse outboard motors for sale, or the parts and accessories to keep one running.