If you run rivers, you’ve probably narrowed it down to a jet boat. The next question is which kind: an inboard jet, where an engine inside the hull drives a jet pump through the bottom, or an outboard jet, where a jet foot replaces the propeller on a standard outboard.
The short answer: inboard jets are built for serious shallow, fast, or rocky water and heavy loads. Outboard jets are a simpler, lighter, lower-cost way to get jet capability on smaller boats and easier rivers. Here’s how to decide.
How an inboard jet works
An inboard jet uses an engine mounted inside the boat, connected to a jet pump at the transom. Water is drawn up through an intake in the bottom of the hull, accelerated by an impeller, and pushed out a nozzle at the stern. Steering comes from turning that nozzle. Stopping and reversing come from a reverse bucket that drops over the nozzle.
Because the intake sits flush in the bottom, there’s nothing hanging below the hull. That’s what lets an inboard jet run in very skinny water.
How an outboard jet works
An outboard jet is a regular outboard motor with the lower unit and prop swapped for a jet foot. The intake sits at the bottom of that foot, just below the hull. The motor still tilts, trims, and mounts on the transom like any outboard.
The tradeoff is efficiency. An outboard jet is commonly cited as delivering roughly 25 to 30 percent less usable thrust than the same motor with a propeller. So a jet outboard is usually rated by its “prop-equivalent” horsepower, and you size up to make up for it.
Inboard jet vs. outboard jet at a glance
| Inboard jet | Outboard jet | |
|---|---|---|
| Shallow-water ability | Best. Nothing below the hull | Good. Jet foot sits a few inches below the hull |
| Power for the weight | Strong; big engines, efficient pumps | Lower; loses some thrust to the jet foot |
| Heavy loads | Handles them well | Better suited to lighter loads |
| Interior space | Engine box takes space mid or aft | Open deck, motor hangs off the transom |
| Upfront cost | Higher | Lower |
| Maintenance | Engine, pump, and cooling system | Familiar outboard service plus jet foot |
| Best fit | Whitewater, rocky rivers, guides, patrol, rescue | Smaller rivers, lighter boats, budget builds |
When an inboard jet is the right call
Choose an inboard jet when the water decides for you. That means fast, shallow, rocky rivers where a strike to the lower unit would end your day. It also means boats that carry real weight, like guide boats with full client loads, or patrol and rescue boats carrying crew and gear.
Inboard jets also handle well at speed. Steering comes from the pump, so the boat turns with authority even in current. It’s why most whitewater and agency river boats run them.
When an outboard jet makes sense
An outboard jet is a good fit if your rivers are moderate and your boat is on the lighter side. It’s simpler to service, easy to swap or repower, and keeps the deck open. If you split time between a river and a lake, a prop outboard may even be the better choice, since you’ll get more speed and fuel economy on open water.
For help sizing outboards, see our post on single vs. twin outboards and what fuel burn really costs.
The hull matters as much as the drive
A jet is only as good as the water reaching its intake. On our inboard jet boats, we build the bottom with a delta pad ahead of the intake so the pump gets clean, solid water. We cover that in detail in why we build jet hulls with a radius bottom and delta pad.
The pump itself matters too. We explain how we choose between Hamilton 214, Hamilton 241, and Southern Jet pumps.
Frequently asked questions
Can a jet boat run in shallower water than a prop boat? Yes. A jet has no propeller or lower unit below the hull, so it can run in water a prop boat can’t. An inboard jet runs shallowest because its intake sits flush with the bottom.
Is an outboard jet less powerful than an inboard jet? For its size, usually yes. An outboard jet is commonly cited as losing roughly a quarter to a third of its thrust compared with the same motor on a prop.
Which is better for whitewater? An inboard jet. It runs shallower, carries more power for the weight, and steers with more authority in current.
Are inboard jets harder to maintain? They have more systems to care for, but routine service is straightforward. See our jet pump care guide for what to check.
How do I know which is right for my river? Tell us where you run, how you load the boat, and how you’ll use it. We’ll recommend the setup that fits.
Talk to a builder
We’ve been building all-welded aluminum jet boats in White City, Oregon since 2003. If you’re weighing inboard vs. outboard jet, call us at 541-826-5400 or send us a message. We’ll help you pick the right boat for your water.