Up until the release of the BF135 and its 150 counterpart, the only four-stroke outboard manufacturer to use chains for driving camshafts was Suzuki. All other brands used toothed belts, which although generally reliable can break without warning.

Should this happen in an "interference" engine, the piston crowns could contact the valves, resulting in very expensive repairs.

But as a result of ongoing product development in the BF135/150, Honda opted for chains to drive the double overhead camshafts. This was a very sensible move, as the camshaft chain also has to drive the twin counter-rotating balance shafts, following the rule of thumb that four-cylinder engines above 2.2lt of piston displacement balance shafts achieve good engine balance and subsequently low vibration levels.

The only belt drive on the BF135/150 is for the alternator atop the engine.

Based on the 2.4lt Euro Accord engine, the powerhead is entirely new and has been reversed 180° from the BF115/130, so instead of the camshaft drive belt drive being atop the engine and the flywheel below it, the camshaft drive is now below it and the flywheel atop it.

The BF135 misses out on the VTEC of its 150 counterpart but retains its Variable Air Intake System. This lengthens the air intake flow at low speeds to increase bottom-end torque, but shortens the flow at high revs (above about 4000) to improve engine "breathing" and increase power. And while it doesn't provide the oomph of VTEC, the demo BF135 has better throttle responsiveness than expected.

Because of its de-rated nature, the BF135 is a better load-pusher than its BF150 counterpart, which in my opinion is a little light on displacement for a four-stroke 150.

Arthur Alexander of CoastLife Marine, which supplied the demo engine, told me the company has had a particularly successful run mounting twin 135s on its popular 7m Markham Dominator cat, and so far no operating problems have been experienced.

Mounted on a Cruise Craft Outsider 575 and spinning a 17in pitch Solas four-bladed stainless-steel prop, the demo BF135 provided plenty of power combined with very good midrange fuel efficiency.

The engine started instantly hot or cold with no oil smoke appearing at any time, and trolled quietly at 600rpm; but from 1000-2000rpm, some harmonic vibration through the hull structure was apparent. Above 2000 revs the engine was not as smooth as Yamaha's F150A, in my opinion.

Providing the anti-ventilation plate was kept at least three-quarters immersed, power astern was good and no cooling water starvation occurred.

Pushing a total of 1650kg including three adults, the trolling average was 4.1kmh using 1.6lt/h, and at 2000 revs we averaged 11.9kmh using 6.4lt/h. A clean plane was achieved at only 20.8kmh on 2800 revs.

At 4000 revs we averaged 44.2kmh using 20.6lt/h, and through full-lock figure-eight turns at 4500 revs there was no prop ventilation. The four-bladed prop also reduced the hull leaning to windward across a beam wind, but due to prop-blade drag compared to a three-bladed prop, the WOT average was lower than expected - 65.1kmh on 5500 revs using 50.6lt/h, where we could still talk normally at the helm.

Servicing the BF135 appears straightforward, with the shrouded alternator drive belt and spin-on oil filter easily reached. Recommended servicing intervals are every 100 hours or six months after the first 20 hours, and the waterpump impeller should be replaced every 200 hours or once a year.

The BF135 complies with US EPA 2006 and CARB 2008 exhaust-emission regulations and has a three year warranty.