MTI 390X Review, the 39-Foot Outboard Cat From Wentzville

"The 340X on steroids", how the 390X came to be

Marine Technology Inc., better known as MTI, builds performance catamarans and center consoles in Wentzville, Missouri, and is one of the dominant names at events like the Lake of the Ozarks Shootout. In late 2019 the company took its popular 340X outboard sport cat and scaled it up. The result, the mti 390x, was unveiled on November 5, 2019, in front of a packed house at Haulover Marine Center in North Miami.

Founder and owner Randy Scism described it simply: it is the 340X on steroids, bigger, more stable and better handling. The boat was built from completely new CNC molds with integrated steps, and Scism credited Mercury Racing's then-new 450R outboard for making it possible. MTI spent days dialing it in at Lake X, Mercury's Florida test facility, before the launch.

Demand was immediate. Hull No. 1 was meant to be the demo but was sold to a customer who made an offer MTI could not refuse, and by January 2020 Scism said MTI had already sold 13.

Specs and the stepped cat hull

MTI lists the 390X at 39.4 feet long, or 39 feet 4 inches, with a 10-foot 6-inch beam, a rigged dry weight of 6,000 pounds, a 150-gallon fuel tank and twin Mercury Racing 450R outboards. Standard seating is for six adults. Those numbers explain the performance: a light, wide, stepped catamaran with 900 hp is a very different animal from a heavy V-bottom.

The hull uses integrated steps at the back of each sponson and a protected cockpit behind a wraparound windshield. Later boats are often full carbon fiber builds, as several dealer listings note, which reduces weight further and adds to the price.

• Length 39 ft 4 in, beam 10 ft 6 in
• Rigged dry weight about 6,000 pounds
• Fuel 150 gallons
• Seating for 6, or 8 with the staggered cockpit option

Twin Mercury Racing 450Rs and 120 mph-plus

The 450R is a supercharged 4.6-liter V8 outboard producing 450 hp, and a pair of them is the signature 390X package. At launch Scism said the boat runs more than 120 mph with 450Rs and would run remarkably well with Mercury Racing Verado 400Rs for buyers who do not want the bigger engines. A 2024 boat offered by Performance Boat Center uses Mercury Racing 500R outboards on STR brackets, showing that MTI has kept pace with Mercury's newer engines.

MTI has not published a certified speed and fuel curve for the 390X, and we have not found an independent magazine test with fuel figures. Treat 120 mph as the builder's claim, achieved by an experienced setup crew with the right props and conditions. Owners who run on lakes with friends aboard typically cruise far below that.

One practical advantage of outboards on a cat this size is maintenance. Compared with MTI's sterndrive-powered 48 and 52-foot cats, the 390X avoids drive and exhaust systems, and engines can be serviced or replaced as complete units by Mercury Racing dealers.

Six seats or eight, and the custom cockpit culture

The original 390X seated six, with two seats up front behind the wraparound windshield and four across the back, similar to the 340X. In June 2020 MTI introduced an optional eight-seat cockpit after customers asked for something closer to the layouts in its bigger 48 and 52-foot cats. The staggered arrangement adds two seats outboard of the driver and co-pilot, so four people sit behind the windshield and can talk easily.

Like most MTIs, the 390X is heavily customized. Owners choose paint or wraps, seat layouts, electronics and color schemes; Speed on the Water has covered boats with themes inspired by watches, special six-seat layouts for poker runs and canopied versions. Scism has noted that wraps save months of paint-booth time, while paint remains the choice of most buyers.

The 390XR and the 450R Factory Stock class

The 390X also became a racing platform. MTI developed the 390XR raceboat version with a safety canopy for the American Power Boat Association's 450R Factory Stock class, a class for catamarans powered by Mercury Racing 450R engines. By the 2022 St. Petersburg Grand Prix, three 390XRs were racing in the class, and MTI offered a concierge service that provides a complete crew so the owner only has to show up and drive.

The canopy layout also found buyers who do not race. MTI built canopied 390XR pleasure boats, and a race-ready 2023 390XR listed for $1,099,950 shows that the racing version carries a premium over standard 390X sport cats.

What it takes to own an outboard cat at this speed

Running costs depend heavily on how hard and how often you run. Plan on roughly $30,000 to $80,000 a year for specialized insurance, Mercury Racing service, storage, trailer upkeep and fuel. Insurance carriers will look closely at the driver's experience with catamarans above 100 mph, and formal high-speed catamaran training is worth considering.

Catamarans behave differently from V-bottoms. They are extremely efficient and fast in flat to moderate water, but they demand careful trim and throttle management in rough conditions, and the consequences of a mistake at triple-digit speeds are serious. The 390X's larger size is part of its appeal: Scism said it is more stable than the 340X, and a customer at Lake X said it turned remarkably well for its size.

MTI 390X for sale, reading the listings

Because MTI has built a healthy number of 390Xs since 2019, there is a steady flow of used boats through performance dealers such as Performance Boat Center, American Custom Marine and MTI itself. Recent listings ranged from $579,900 for a 2022 boat with about 250 hours to $899,000 for a 2024 carbon boat on 500Rs with 65 hours.

When comparing mti 390x for sale listings, check engine hours and remaining Mercury Racing warranty, whether the boat is a standard or full carbon build, the seat layout, and whether it includes a trailer. Also ask about any racing history if you are looking at a 390XR.