It’s no secret that outboard-powered fishing boats are reaching new benchmarks, with some 60+ footers out there in the marketplace. The problem is that the manufacturers of the largest conventional outboards to date, specifically the Yamaha F350C, Suzuki DF350 and the Merc 350 and 400 supercharged Verados, were not realistic options. Seven Marine dominates the market for super-sized 50- and 60-footers with their GM automotive powerplants that are specially built and marinized to produce either 557 or 627 sea ponies at the propshaft. These engines cost anywhere from $110,000 to $125,000 each, and factory authorized mechanics are few and far between, especially on a busy holiday weekend or 100 miles offshore. Enter Yamaha Marine with their new 425 XTO Offshore “Extreme” four-stroke outboard.
Pushing the heaviest offshore boats and yachts requires driving extreme, large propellers, a massive, rugged gearcase and an extreme powerhead. As the first four-stroke powerhead in the outboard industry to use Direct Injection, the V8 XTO Offshore is already a legend, spraying fuel at high pressure directly into the combustion chamber, rather than the intake track, just before the intake valve. This greatly improves atomization and increases the effectiveness of the fuel burn for maximum power and efficiency.
The Direct Injection system features five fuel pumps and injection pressure up to 2900 PSI. The three-stage fuel pressure system is in part comprised of two independent fuel pumps within the Vapor Separator Tank (VST) that activate at specific, individual RPM. This ensures proper fuel flow and delivery, even at very high engine RPM. Yamaha’s V8 XTO Offshore also boasts the highest compression ratio in an outboard at 12.2:1. This means more “bang” from every spark, as well as better efficiency and power.
In addition to an oversized gearcase, hardened gears, a robust, offshore bracket and motor mounts, the V8 XTO Offshore outboard also features proven plasma fusion technology for durability and lighter weight. The outboard also has a two-stage water pump and dual chamber oil pump, each designed to respond to the heavy loads associated with high RPM operation. Dual overhead, endurance-driven camshafts on each cylinder bank are connected via a self-tensioning chain immersed in an oil bath for accurate valve timing and long life, delivering quiet and precise connection for proper and consistent valve timing. One sprocket belt engagement means a narrower, more compact overall profile.
The new V8 XTO Offshore outboard also features quad thermostats, two thermostats per cylinder bank, for improved flow and better regulation of engine and oil temperature. A uniquely designed two-stage water pump features a massive rubber water impeller for high pressure and flow. A steel impeller helps provide sufficient water volume even under the most extreme offshore conditions. The V8 XTO Offshore has integrated electric steering, the first of its kind in any outboard. The integrated steering system has no hydraulic lines or linkages, and responds more quickly than conventional systems to steering inputs. It also features an Integral Electronic Steering Control Unit that receives signals from the steering cylinder position sensor to carry out joystick and steering operation.
Initial factory tests with a variety of oversized sportfishers have indicated that the new Yamaha 425 XTO (retail prices starting at $44,000) will get the job done at a fraction of the cost of the larger automotive marinized conversions. A Contender 39ST center console powered by a trio of these big V8s produced a top speed of 72.7 mph at 6000 rpm with 0.98 mpg fuel efficiency at 3500 revs, where she registered 36.6 mph on the GPS navigator. Grady-White’s new “beast,” the Canyon 456 center console, hit a top end of 58 mph at wide open throttle and 0.64 mpg at 4000 rpm, where the big Carolina girl cruised along at 36.8 mph. Mounting a pair of 425 XTOs on a Grady Canyon 336 CC produced some more realistic fuel efficiency numbers with a top speed of 54.7 mph and a cruising speed of 31.7 mph at 3500 rpms, consuming 23.4-gph for a bottom line of 1.36 mpg…most of us could live with those numbers on a solid boat that can blast through opposing head seas in comfort.