Honda BF225

The BF225 provides comparable performance to a 225hp direct fuel-injected two-stroke outboard. It returns the same fuel efficiency when trolling as its FICHT and Optimax competition but significantly better fuel efficiency at Wide Open Throttle for the same performance. Yet because it's a four-stroke it has much lower oil consumption and subsequent emissions than even the DFI motors, particularly when trolling.

These were the comments I made to Honda MPE after having spent several days in mid-November on the Gold Coast testing two BF225 models. Honda's Ray Barnes, Solas Propellers' Steve Evans and I tested these motors on two very different hulls. We tried six different props on each, using a portable Navman digital flowmeter and two separate GPS units for accuracy. We exhaustively tested the motors in conditions from a 15cm chop off Runaway Bay to a 1.5m sou-easterly swell off the Southport Seaway.

And all this testing paid off, leaving me with the impression that Honda has created the world's most throttle-responsive four-stroke outboard. I thought that Yamaha's F225A was good, but across their entire rev ranges the Honda had the distinct edge for both performance and fuel efficiency. The BF225 is also a 'three star' motor and complies with the California Air Resources Board (CARB) 2008 regulations, whereas the F225A is only a 'two star' motor and complies with CARB 2004.

Apart from its greater piston displacement, the BF225 also has the advantage of both VTEC and a variable air intake system. The former overcomes the valve-lift compromise found in most four-stroke engines and hydraulically increases the valve lift by swapping the camshaft lobes. Below 4500rpm lower-profile lobes are used to ensure a good blend of torque, while above these revs the intake valves open higher and longer to produce more power.

In most four-strokes the volume of air intake is controlled by the length of the intake manifold. But in the BF225 the volume of air is varied using two valves to again produce more torque at low revs and more power at high revs.

At low revs the valves are closed and each cylinder bank is isolated creating a specific resonance effect which generates high-pressure waves of air in the manifold and increases torque by ramming in more air.

But at 4000rpm these valves open and the manifold air volume is doubled, which, combined with the VTEC, allows the engine to breathe much better and produce a dramatic increase in power. When passing 4500rpm with the throttles wide open both Hondas have an almost turbo-like boost and want to keep accelerating right out to WOT, giving throttle-responsiveness more akin to the Optimax 225 than the F225A.

Although we were not able to test the Hondas on the same hull as the F225A, we got pretty close, especially on the Haines Hunter 680SF. The 680SF displaced a total of 2050kg whereas the Yamaha was on a Southwind SF640 which displaced 1800kg, so the longer planing surface of the Haines was cancelled by the additional weight.

We found the best all-round prop (the others suited more specific purposes and returned even better fuel efficiency at certain revs) was the 14.5 x 17in four-blade Solas Torquemaster.

At Dead Slow Troll and 650rpm the BF225 averaged 8.7kmh, used just 1.7lt/hr and returned 140% better fuel efficiency than the Yamaha, while at offshore troll revs of 2000 the Honda averaged 14.7kmh, used 7.2lt/hr and returned 70% more efficiency.

At the minimum clean planing speed of 30.8kmh and 3100rpm, the Honda used 21.0lt/hr and returned 20% better efficiency. At 4000rpm it averaged 49.9kmh and 35.0lt/hr and returned 10% worse efficiency than the Yamaha.

Through tight figures of eight at 4000rpm the Torquemaster prop refused to ventilate and out to WOT helped stabilise the 680SF over a half-metre chop.

The WOT average was 78.3kmh on 5900rpm, using 77.0lt/hr and returning almost exactly the same fuel efficiency as the Yamaha but 5.5kmh faster. The Honda was slightly noisier than the Yamaha at WOT, but this was a small price to pay for the performance increase.

Both of the multipoint-injected test motors started instantly hot or cold, warmed quickly and never blew any oil smoke.

The warranty coverage is three years for recreational applications.