Yamaha - Increasing the pressure

Yamaha continue to add to the high technology field of outboard motor engineering with the introduction of two new outboard motors and a long-awaited, four-stroke personal watercraft.

One of these impressive additions is the Z250D HPDI, which is based on the EFI 250B. Along with the addition of HPDI (High Pressure Direct Injection), which replaces the original EFI system, a larger cylinder bore increases the Z250D's engine displacement by 200cc. Figures quoted by Yamaha record a 10% increase in torque in the low and mid speed ranges and improved acceleration. Dual pumps replace the original single unit seen on the 200hp model, increasing the injection pressure to 7Mpa.

Yamaha believe they have achieved higher output power, lower fuel consumption and a cleaner running outboard with these modifications.

A cowling design change further resists water intrusion, while the lower unit has been reinforced. Yamaha also quotes up to 45% improvement in fuel economy when compared with the EFI 250B model and has conducted exhaustive testing comparing these two outboards.

Under the new cowling is a 76° V-six block with a displacement of 3342cc. The bore and stroke is 93mm x 82mm, giving a compression ratio of 6.2:1. It has a maximum operating range of between 4500rpm and 5500rpm and develops its maximum horsepower at 5000rpm. Gear ratio is 1.81:1 (29/16) and dry weight 252kg. Alternator output is 50amp, developing 37amps at 1000rpm.

We tested the Z250D bolted to a Southwind SF640 and found it to be very quick off the mark. Hole shot was very sudden and acceleration to 75kmh GPS speed even more rapid. Cruising at 60kmh and hitting the throttle was enough to jar the neck! Also surprising is how quiet this engine is for such a large horsepower two-stroke. It made for comfortable travelling at all speeds without the expected high-pitch noise.

SMALL BUT SWEET
At the other end of the spectrum, Yamaha have catered for those looking for a light and portable water-cooled four-stroke outboard. The F2.5A has a dry weight of 17.0kg for a shortshaft model and 17.5kg for a longshaft. It features a single cylinder overhead cam motor, with a displacement of 72.3cc, fed by a single carburettor with a manual choke. Fuel tank capacity on this model is 0.91lt and it has a recoil manual start system.

This unit has a four-step tilt position, forward and neutral gear positions and is able to rotate 360° - negating the need for a reverse gear. The gearbox ratio is 2.08:1 or (13/27). And with a choice of five different pitched propellers, this little unit will find favour among cruiser and yacht owners as a motor for their tenders and among canoe operators looking for economical high speed. It also has a manual drain device for the carburettor, so that it may be easily and quickly emptied and stored laid down. These features make it ideal for those car-topping a small boat and storing the motor in the boot or the back of the 4WD.

It would be a mistake for marine engine manufacturers to ignore the mood of the boating world and the many non-participants waiting in the shadows to pounce on anything non-environmentally friendly. Blind Freddy could see the massive swing that the marine industry has undertaken in the last five years. Yamaha is one of the pacesetters in terms of being progressively 'greener' with exhaust emission and noise controls on their motors.

SPECIAL FX
The personal watercraft market is huge and rapidly growing. So when a government body bans the use of these craft on Sydney Harbour, it must alarm those who have spent millions on research and development to get the market to where it is today.

Enter Yamaha's WaveRunner FX140 four-stroke personal watercraft. It features the MR-1 powerplant, which is derived from the YZF-R1 racing engine, and claims to be up to 84% cleaner in emissions than some two-stroke models. Yamaha's claims of reduced noise and emissions were verified when we saw this craft on test at the Gold Coast. It is hard to quantify how much quieter the FX140 is, but at close quarters the noise at full throttle is noticeably lower than in two-stroke models.

These results should be ascertained and conveyed to relevant authorities to prevent further closures of waterways to PWC riders. Many of our inland waterways are likely to allow four-stroke propelled vessels only. It would be a win for the green minority, which has disproportionate influence with government, to have more craft removed from these waterways. Yamaha's move into four-stroke PWCs is indeed one in the right direction.

The FX140 is a three-seater PWC that measures 3340mm long, 1230mm wide and 1160mm at its highest point.

Its dry weight is 362kg and its maximum horsepower of 140 is developed at 10,000rpm.

The four-cylinder water-cooled motor features a double overhead cam with a displacement of 998cc. It has a high compression of 11.4:1 and runs a wet exhaust and dry sump. It also has an electric starting system running off a 19Ah battery, which is fed by an alternator generating 15A at 6000rpm and a lighting coil for accessories generating 14-16amps at 6000rpm.

The axial flow, single stage jet pump propulsion system utilises a reverse gate and the transmission is constant mesh, single speed. It has a reduction gear ratio of 19/28.

The steering nozzle turns 24° each side of centre and it has trim angle of -10, -5, 5 and 10°. The manual trim adjustment system has five positions. Engine oil capacity is 4.3lt and the fuel capacity is 70lt.

The FX140 displayed similar speed and agility to a two-stroke PWC. The biggest difference was, in fact, the lack of noise - and all will welcome that.