There was a twinkle in the eyes of the Yamaha bass pros on hand at the Yamaha V MAX SHO media launch in Bridgeport, Alabama this week. They were our escorts during test runs of the new motors on Skeeter boats, and they can’t wait to get these rigs out in a tournament. Here’s why: With this new 4.2-liter V6, Yamaha has produced a four-stroke bass outboard that’s as light as any high-performance two-stroke motor. Which means that the last excuse you might have for not considering a four-stroke may no longer be applicable.
The four-stroke V MAX SHO combines prodigious bottom-end power and lighter weight to deliver outstanding hole-shot – that’s acceleration from a standing start – that will get a tournament angler to the hot-spot first, and is just plain thrilling for the rest of us. Yamaha claims the acceleration performance is better than any two-stroke in the class, and 13 percent better than the old two-stroke V MAX. Top speed is comparable to the Merc and Evinrude bass engines, according to Yamaha. Of course, I can’t verify any of that. I can tell you that when I mashed down the foot-feed on a Skeeter 21FX, the boat planed off in less than three seconds and topped 75 mph. Yamaha says the four-stroke V MAX delivers 12 percent better average fuel economy than its two-stroke V MAX, and of course it does not burn injector oil. Note also that the new V MAX has a three-star emissions rating, where the two-stroke Max was a two-star motor that could not be sold in California.
As Light as a Two-Stroke
Yamaha will offer 4.2-liter V MAX SHO motors rated at 200, 225 and 250 hp, and only for 20-inch transoms. These motors will replace the V MAX Series 2 two-stroke models in 2010. Yamaha says each of these motors – which are identical except for the power rating – has a dry weight (no oil or prop) of 505 pounds. That’s 34 pounds less than the two-stroke V MAX models they replace, and within a few pounds of the two leading contenders in the high-performance bass-boat segment, the Mercury OptiMax Pro SX 250/225 (505 pounds) and the Evinrude E-TEC 250/225 HO (507 and 503 pounds). The weight of the two-strokes also does not include a prop or the oil reservoir and oil.
All New Powerhead
The 4.2-liter powerhead is all-new but will still be familiar to Yamaha fans. With a 60-degree cylinder angle, double over-head cams, and the exhaust ports facing each other (Yamaha’s “in bank” exhaust arrangement) the basic layout is the same as previous Yamaha V6 four-strokes. Electro-mechanical variable cam timing on the intake side is offered at all three power ratings. That feature combines with a 75mm throttle body and long, tuned intake runners to significantly boost low-to-mid-range torque, according to Yamaha. Full-throttle rpm range is 5000-6000, with peak power rated at 5500 rpm. The 200 and 225 are happy on 87 octane fuel, while the 250 will make peak power on 89 octane, though it will run on 87.
Perhaps the key technical highlight of the new powerhead is the sleeve-less cylinder design that replaces typical steel liners within each aluminum cylinder bore. An alloy dust of chrome, nickel, manganese and other elements is super-heated in a plasma process and fused to the cylinder. This saves about 6.2 pounds of weight and permits about 2mm more cylinder bore in the same block size. The coating is said to be 60 percent harder than steel and thus very wear resistant. It also offers a “micro-texture” surface (think about the dimples on a golf ball) that holds oil to further reduce wear, aid cooling, and significantly reduce friction, which in turn enhances both power and economy. This texture is really micro. To the naked eye the surface looks smooth as chrome.
Further weight reduction was achieved through careful casting techniques and little things like trimming excess steel from the camshafts and using new plastic cam covers. The V MAX SHO cowl has a “spoiler” shape similar to the previous two-stroke V MAX but is molded with a new, lightweight composite material. Unlike the Offshore version of the 4.2-liter powerhead, the bass version does not have a muffler on the exhaust relief. According to Yamaha, this cut another 20 pounds from the overall weight of the motor and gives the V MAX a little more growl at idle. The V MAX also has a smaller, lighter alternator that uses rare-earth magnets and makes 50 peak amps and 46 amps at 1000 rpm. A new mounting bracket is 29 percent lighter than the previous V MAX bracket. A new composite lower pan (the bodywork directly below the cowl) replaces the previous aluminum pan and saves 12.7 pounds. The mid-section was re-shaped to cut 11 pounds.
Built for Bassin’
The new V MAX gearcase is designed for high-speed work, with a crescent-shaped leading edge. The skeg is curved to port to help counter prop torque at high trim angles. The gear ratio is 1.75:1, same as that of the Offshore models, but the V MAX gears have been specially heat treated for added strength. The new case has a single water pick-up on each side, mounted low and forward on the bullet, and they are 81 percent larger than the inlets used on the two-stroke V MAX.
Because most high-performance bass boats are rigged with a cable-actuated foot throttle, the four-stroke V MAX motors are not compatible with the Yamaha Command Control digital levers, although the throttle control is “drive-by-wire” once the cable enters the engine. This motor can drive any of the Yamaha Command Link instrument displays. However, the new Yamaha “YCOP” digital anti-theft system is not available with the V MAX.
To make the most of four-stroke V MAX power, Yamaha has designed a new series of V MAX Ventless propellers specifically for the new 4.2-liter motors. These high-rake, stainless steel props are offered in 23- to 29-inch pitch. They are called "ventless" because they do not have vent slots at the base of the hub, which are a feature of the original V MAX-series props designed for the two-stroke V MAX motors. Those vents help a two-stroke outboard rev quickly into its powerband, but would hurt the performance of a four-stroke. In fact, Yamaha says those vented V MAX props should not be used on the new four-stroke V MAX motors.
Yamaha owns the Skeeter boat company, and Skeeter was in on the four-stroke V MAX project. Its new Skeeter 20FX and Skeeter 21FX boats were designed specifically for the new outboards. The weight distribution of the boats, for example, was determined with the weight of this motor as part of the calculation, and the shape of the aft hull was designed to feed a thick trough of water to the prop as the boat climbs on plane to further enhance hole-shot. In my short test drive, I also found that the hull helped keep the prop hooked up in low-speed 180-degree turns – the kind you might execute to go back and get your cap after it blows off. The boat stayed on plane, never blew out the prop, and then accelerated smartly back up to speed. Despite the lack of a muffler, the V MAX is super-quiet. Maybe too quiet for this market. Call me nuts, but I think one reason the bass crowd likes a two-stroke is that it loves the sound.
Yamaha did not offer any pricing information at this meeting, and would not let me take any under-cowl photos because the motors we ran were pre-production examples. Maybe Yamaha still has some patents to secure. The V MAX SHO models are in production in Japan, and will begin appearing at dealers in time for January boats shows, according to Yamaha, and will be on the water when the B.A.S.S. Bassmaster Classic kicks off on Feb. 20 in Shreveport, Louisiana.