World first for this clever outboard

A new Suzuki that can be used in either "normal" or "counter-rotating" modes could change the way we buy outboards.

It is one of those facts of life that every marine engineer or competent outboard seller learns on the first day on the job: if you are going to put two outboards on the transom, one of them needs to be a counter-rotating model.

The counter-rotating model spins its propeller in an anti-clockwise direction and is placed on the port side of the transom. The starboard engine is a standard outboard and its prop spins in a conventional clockwise direction.

This ensures the tops of the two propellers spin away from each other and creates a well-balanced, symmetrical push through the water.

If one simply fitted two engines that spun clockwise, they would throw dirty water at each other and create unwanted cavitation (aerated water around the blades).

The two matched engines would also create a tendency for the boat to list to starboard (due to propeller torque pushing it that way), make it far harder to manoeuvre at low speeds and produce more noise and through-hull vibration.

However, according to Martin Beeson, marketing manager at Australasian Suzuki distributors The Haines Group, there are some significant drawbacks with counter-rotating models.

"The resale value of a counter-rotating model engine is far lower than a normal engine," he says, "and customers do not like purchasing a single counter-rotation engine for their boat."

From next month, that will not be a problem, at least for those who buy Suzuki's new 300hp outboards. If they want a dual-engine installation, they will no longer have to buy the two different models - they can simply purchase a pair of Suzuki's new DF300AP outboards and use their new Selective Rotation system.

Suzuki claims the DF300AP is the first outboard (or stern drive leg) in the world that can operate in either forward (clockwise) or reverse (anti-clockwise) direction.

In its standard form, the new model will operate in regular clockwise rotation, using the forward gear. If one then wants to add a second counter-rotating engine, they simply buy another stock-standard DF300AP, use the selective rotation system to change the gear shift and buy a counter-rotational propeller.

In this counter-rotation mode, the outboard's forward power is simply transmitted through the reverse gear, and vice versa.

To ensure that the reverse gear can handle this new and prolonged load, Suzuki's engineers not only "upgraded and improved" the reverse gear to give it the same characteristics as the forward gear, they "optimised" both the specifications and the materials used in both gears - and improved the layout of the bearings.

In order to accommodate the new gear system, the engineers also re-designed the gear case.

According to Beeson, they made several other improvements, too.

"By using accumulated fluid analysis technology, the new gear case has been designed to provide reduced resistance and improved durability," he says.

"At the same time, a structural analysis was carried out in order to optimise each and every component."

Beeson says Suzuki's engineers also redesigned the DF300AP to feature two water intakes on each side of the gear case (the current DF300 has just one on each side).

"These additional water intakes ensure stable cooling performance at high speeds and during shallow water operation," he says.

"Ultimately, by eliminating the differences in specification between regular and counter-rotation models, Suzuki has achieved what no other outboard manufacturer has been able to do - unification of both regular rotation and counter-rotation operations into a single outboard model."

Beeson says the DF300AP, which has just been awarded the NMMA Innovation Award at the Miami Boat Show, will be available in New Zealand and Australia next month.

"Smaller horsepower Suzuki models with Selective Rotation will also be available in the future," he says.