Honda's great leap forward

Increased fish stocking in Australia's east coast impoundments has seen a big surge in the popularity of larger boats purpose-built for bass and barra anglers. A decade ago, the average river and lake boat was generally a 3.7m dinghy or punt with a 15 or 20hp two-stroke outboard. Today the norm is a 4m-plus boat with flush casting decks, livebait tanks complete with reticulation systems, steering consoles and at least a 40hp engine bolted on the transom.

This trend has been mirrored in many of Australia's recreational fisheries and the massive growth in this area has left an almost equally large void in the smaller outboard market, particularly motors between 8 and 20hp.

Honda understands there are still buyers that want small boats for financial or weight-related reasons.

Honda hopes its introduction of four new fuel-efficient and environmentally friendly units in the 8, 10, 15 and 20hp four-stroke range will satisfy that demand.

WEIGHT WATCHERS
The company has made a number of design alterations that has shaved weight from the larger of the small powerplants, the 20hp. The outboard now weighs in at just over the mass of the older model BF15 four-stroke. The other models in the range have also lost weight.

To achieve this reduction, Honda has replaced alloy components with resin materials under the cowling, which helped reduce overall weight compared with the older model BF15. The recoil starter is now made of resin material, reducing its component weight by 12% over the previous model. The belt pulley and tiller handle is also made of resin, saving 16 and 26% over the old alloy components. These and other lighter parts combine to shave about 3-4kg from the overall mass, with the BF20 now tipping the scales at 47.56kg.

TWEAKED CARBIES
The new 20hp outboard has a mechanical decompression device to assist with easy starting. Two separate decompression cams attached to the camshaft lift exhaust valves to make pull-starting a breeze.

Honda technicians have also been hard at work in the carburettor department. The guesswork of how much choke to use on a particular day is now eliminated with the abolition of the choke knob and the introduction of the Starting Enrichment system (SE). On recoil-start models a plunger allows air in to vaporize a richer fuel mixture, and on electric-start models a temperature control device is installed. This plunger type switch actuates on current from the heating coil and provides a gate in the passage from the air cleaner to the intake manifold while controlling the aperture from the float chamber. Which adds up to easier starts first time.

When a throttle handle is turned full on, the throttle valve opens quickly and the airflow velocity at the venturi slows down, decreasing the vacuum. Consequently the fuel mixture becomes too lean due to the decrease in quantity being sucked in and the engine runs lumpy and can stall. The inclusion of an accelerator pump now provides quick acceleration and improved throttle response. The smoothness when compared with the older BF15 outboard was noticeable on acceleration from a standstill with no hesitation or 'lugging' evident.

Another new feature on this series of outboards is the Carburettor Primary Circuit. Previous slow and complicated fuel galleries have been replaced with a primary circuit that achieves smoother acceleration and improved fuel economy from idling to full throttle.

Vapour lock has been one of the big hassles of combustion engine users since Otto first described his 'cycle' that typifies four-stroke engines. When a warm or hot outboard is restarted and given full throttle, cold fuel from the tank rushes into a warm carburettor, vapourises and blocks the lines. Honda has interrupted this process with the installation of a fuel chamber between the fuel pump and the carburettor, allowing the fuel to be warmed slightly before entering the carburettor.

This reduces the likelihood of vapour lock.

USER FRIENDLY
A locking collar behind the throttle handle allows for tensioning or locking of the throttle setting, easing arm ache during long trips. Beneath the collar is the push button start, eliminating the need for a key.

Complimenting this is the inclusion of steering friction adjustment that makes holding the tiller during periods of high torque more comfortable. It's good to find a comfortable level of handling and movement when travelling long distances and the mechanism is tucked away neatly under the base mount for the tiller arm.

Honda has installed a refined ignition system referred to as PGM-IG, which enhances running performance and economy over the entire rev range. This function also acts as the electronic control monitoring system to protect from over-revving, low engine oil pressure damage and overheating.

These new Hondas come standard with a four-blade propeller designed to provide maximum lift out of the water when carrying heavy loads. It also keeps the transom high allowing the boat to plane at lower speeds ... just what you need to travel economically in a heavy chop. These four-blade propellers are ideally suited to small boats where a single person is aboard at the tiller, giving the boat a more level attitude.

Testing these motors on a bunch of aluminium boats and an inflatable on the Broadwater in front of Sea World, the marked difference in the running and smoothness during acceleration was obvious.

Electric starting was instant and idling was so quiet and low in the rev range that I thought the outboard would stall - but it ran smoothly. The new decompression system works like a charm, making pull-starts effortless. This is in contrast to other motors where each compression stroke can be felt via the rope as it is withdrawn.

After playing around with the tension adjustment lever, I discovered that with it off the engine was very loose and propeller torque was felt at the tiller. With a slight amount of tension applied there was no vibration whatsoever coming through the tiller.

CUTTING EDGE TECHNOLOGY
The new BF175 was also available to test. It was bolted to a 7.3m aluminium Ocean Cylinder, which itself proved to be a pretty smart craft. Set up as a diveboat and with seven people aboard, it flew over steep chop at 60kmh, its smoothness matching that of the new four-stroke on the back.

The BF175 features a 60-degree V6 with single overhead cam and 24 valves. It's based on a 3.5-litre automotive engine. It also features Honda's Variable Air Intake system and the Multi Points Sequential Fuel Injection. Fuel metering and injection timing are determined according to the analysis of 18 parameters controlled by the Engine Control Module, allowing for more precise control of the air/fuel ratio. The ECM also controls the aforementioned Variable Air Intake ignition timing and idling speed.

Multi Points Sequential Fuel Injection is a system utilised on the BF175 and allows each cylinder to be fed fuel one by one rather than by group injection, which is by pairs.

Honda claims that sequential fuel injection is more precise, and the best technology for the lowest fuel consumption. The O2 feedback sensor detects oxygen remaining in the exhaust and the ECM automatically adjusts the amount of fuel to be injected in the next cycle. This result is instant throttle response with superior fuel efficiency.

Honda's own research and development tests indicate that the BF175 is matching speeds of equivalent horsepower two-stroke direct injection and two-stroke conventional engines with comparable acceleration rates.

The BF175 also features an original gearcase with a ratio of 1.87:1. This, along with the slow, vibration-free idling will make it ideal for long hours of economic trolling.

BIG ALTERNATOR
Running banks of electronics shouldn't be a hassle either. At a low 1000rpm this motor is pumping 48-amps from its V-belt driven multi-polar alternator. From 2000rpm onwards, it delivers 60-amps on demand.

The V-wing design allows for a pair of outboards of this size to be mounted just 660mm apart. Counter-rotating propellers are available on extra and ultra long shafts.

This outboard motor has a three-star California Air Resources Board (CARB) rating, its ultra-low emission levels complying until 2008.

With such a leap forward in research and development, particularly for the near forgotten low horsepower engine market, I couldn't help but to be impressed. Honda, with this latest line up, has produced another five very smooth engines for its stable.