A question of drive

Chris Beattie | VOLUME 25, ISSUE 6

Sterndrives are becoming more popular in smaller craft. We hit the water to find out why.

Sterndrives used to be almost exclusively found on larger boats, predominantly of 7m and larger. But as technology in so many other areas has resulted in things becoming smaller and more compact, so sterndrives have begun turning up in smaller craft. And nowhere is this demonstrated more clearly than in a 5m tinnie we recently sampled in Melbourne.

A while back, the folks at Mercury called to see if we’d be interested in sampling a small trailerable craft that had been fitted with one of the company’s compact new sterndrive packages. They wanted to demonstrate the differences inherent in a smaller sterndrive craft over a more conventional, outboard-powered equivalent.

According to Mercury, the sterndrive option is becoming more popular in smaller craft as people become aware of the advantages they can offer. And, helpfully, they just happened to have a spare boat with one of their outboards attached to trial side by side with the sterndrive variant.

A little while later I found myself at Melbourne’s National Water Sports Centre in Carrum, with two Quintrex 510 Freedom Cruisers bobbing lazily at the jetty.

From the helm forward, both were virtually identical. New for 2010, the Freedom Cruiser is a boat intended as a family-friendly craft that can cater for various activities, from fishing and cruising, to skiing or boarding. Basically, it’s an all-rounder with a bow rider layout that can perform a variety of roles in a range of environments. And designers have managed to cram a lot of features into this compact and agile boat.

OPTI VS MERC

For the purposes of our exercise, our two methods of propulsion consisted of a 90hp Mercury three-cylinder, direct-injected, two-stroke OptiMax outboard – a popular and fairly conventional package, according to Mercury’s Anthony Brown. In the other corner, we had a sterndrive layout consisting of a 135hp, 3lt, four-cylinder, four-stroke MerCruiser inboard hooked up to a Alpha One leg.

Both craft are rated for up to six people and boast good, open layouts that would suit families of all shapes and sizes.

From a layout point of view, the differences are obvious and related, of course, to where the engines are fitted.

In the case of the sterndrive boat, the engine sits inboard of the transom and, while a very compact unit, it can’t help but intrude into the cockpit space. However, from an aesthetic point of view, the upholstered engine cover looks good and is further enhanced by the wrap-around, full-width seat, with comfortable seating for three to four.

But while the inboard steals space from the cockpit, it allows designers to add a full-width swim/boarding platform on the other side of the transom. For those who like their watersports, this is a welcome plus that really adds some serious recreational utility to a relatively small craft.

Other advantages of the inboard layout, according to Mercury, include a low centre of gravity, which aids stability and tends to result in a flatter ride angle when underway, while the standard fitment power steering makes the skipper’s job a bit easier.

CLEAN ’N’ GREEN

The engine itself is also a fairly torquey little number, which will suit anyone wanting to enjoy a spot of skiing or boarding. It’s also clean burning, courtesy of a catalytic converter to meet strict US emissions limits – a very important consideration in our modern clean and green world.

The outboard-powered version of the Cruiser was a pretty conventional craft in terms of specification. With the 90hp OptiMax bolted to the transom, cockpit space is freed up for fighting room for the fishers of the family. And while the engine placement doesn’t allow for a full-width swim platform, Quintrex has still found room either side for adequate boarding platforms and rails.

An interesting addition on the OptiMax-powered boat was Mercury’s new SmartCraft MercMonitor with ECO-Screen, which is an optional upgrade on all SmartCraft-compatible engines. Providing constant information on speed, trip distance, fuel used and trip time, it also has an ‘ECO’ function, which compares a range of input to determine optimum fuel usage settings. By varying throttle settings and trim, the driver can achieve the best possible fuel consumption, which results in the screen turning an appropriate shade of green. If you’re out of the ideal envelope, it turns a disapproving shade of yellow.

The system is NMEA 2000 rated, which means the information can also be displayed on compatible non-Mercury electronics, such as chartplotters and GPS units.

On the water, the various characteristics of both craft were fairly immediately obvious.

EASY RIDER

Once on the plane, the sterndrive Cruiser tended to ride flatter, courtesy of its more forward-biased weight balance and lower centre of gravity, while the power steering meant no effort required at the helm. Given the relatively low seating position, it meant that forward visibility was excellent – an important consideration when towing skiers in confined waterways.

The OptiMax-powered boat was definitely punchier out of the hole, but didn’t have quite the broad and even torque spread of the larger four-stroke, which is what you’d generally expect.

From a performance point of view, both boats rose to plane relatively easily, with the inboard outpacing the outboard in WOT to the tune of 74km/h at 4900rpm, versus 64km/h at 4800rpm. In real world terms, there wasn’t really a lot in it, while the same can be said for fuel consumption. Using a lazy cruise figure of around 30km/h, the figures for each boat worked out at around 9-10lt/hr.

Pricing worked out at a recommended retail for the inboard of $43,400, while the OptiMax option came in at $41,600, although you’d have to add around an extra $1500 on the outboard for equivalent power steering.

The object of the exercise had been to showcase the features of the inboard option on smaller trailerable craft and I came away thinking that, from a family perspective, it’s certainly well worth considering, depending on the sort of boating you do. If it’s predominantly about watersports and putting smiles on dials, plus a bit more comfort factor, then the MerCruiser option might be right for you. And if you feel like wetting a line, there’s plenty of room for that, too.

For more information, contact your nearest authorised Mercury dealer, or go to: www.mercurymarine.com.au. ¿


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