The outboard jet is a type of outboard boat motor that is popular in shallow and rock-filled waters. These types of hazardous waters are notorious for breaking propellers and damaging lower units on outboard motors. By placing an outboard jet on a boat, the propeller is replaced with an impeller mounted inside of a modified lower unit housing—there are virtually no moving parts outside of the motor to break from contact with rocks. The other benefit of the outboard jet is its ability to operate in a very shallow body of water. In most cases, if there is sufficient water depth to float the boat, the outboard jet will operate and propel the craft.
Originally offered only in an inboard-outboard configuration, the jet propulsion system was used on sport boats and larger military craft. Fishermen and duck hunters sought an outboard boat motor that would allow them to enter very shallow waters without the resulting damage of hitting rocks and submerged logs and tree stumps with the motor's propeller. There also was a need for propelling a boat through very fast and rocky waters, such as rapids, while fishermen were attempting to travel upstream in search of spawning fish.
The technology which powers individual watercraft eventually made its way into the outboard boat motor manufacturing world. By mating an impeller-style lower unit onto a traditional outboard boat motor, the outboard jet was born. From a technological viewpoint, the outboard jet is a product that was past due. The design was readily accepted by the sport boating community as well as the hunting community. The cost, while a bit higher than a traditional outboard boat motor, is still competitively priced with other motor design styles in the same size class.
One downside of the outboard jet is the required horsepower to operate the jet unit. It requires more power to operate than a propeller-driven outboard, so it is typical for a boat owner to purchase an outboard jet in a larger horsepower rating than the propeller motor that is being replaced in order to have the same performance properties as the previous motor provided. This increase in motor size adds up to an even larger increase in price over simply switching to the outboard jet. For most boaters making the switch, this is a moot point, because the damage to a propeller-driven outboard can often be more costly to repair than the one-time added expense of making the switch to a jet.