Technology - Big-hearted middleweights

Last updated 16:11 16/10/2008

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Responding to demand for lighter, snappier and more fuel-efficient outboards in the middle part of their horsepower range, Suzuki has introduced a trio of four-cylinder, four-stroke engines based around a new 1500cc block.

The new engine family comprises DF70, DF80 and DF90hp EFI models, replacing Suzuki’s current 1300cc DF70hp and two-litre DF90hp models.

The new engines feature double overhead camshafts, four valves per cylinder, and gear-driven timing chains rather than timing belts. Ignition is fully transistorised and electronic fuel injection (EFI) is used to deliver the fuel.

The 80hp is an addition to Suzuki’s range, which now includes 60, 70 (new), 80 (new), 90 (new), 100 (new) and 115hp mid-range engines. Suzuki’s old 90hp engine has been upgraded to 100hp, the first example of which NZ Fishing News also tried.

NZ Fishing News had the opportunity to test-drive a pair of Suzuki pre-production engines in the South Island recently, the first of the new engines to be run in Australasia.

Pre-production Suzuki DF80hp and a DF90hp, as well as the first new 100hp in the country, were delivered to John Butler Marine in Christchurch. The 90hp was bolted to a 530 McLay and the 80hp to a Reflex Chianti 485. We spent two days with the boats, one in Lyttelton Harbour and the other at Akaroa, running them in a variety of conditions, trying different props and generally getting to know them in the company of Suzuki New Zealand technical staff.

On the evidence of our trials, the new models offer a step up in performance and fuel efficiency over the models they replace, as well as refinement.

The new DF70hp is marginally heavier than the old 70hp (156kg against 152kg), but increased capacity (1500cc versus 1300cc), increased torque and changes to the fuel injection and variable-valve-timing systems result in a much improved performance.

At the other end of the range, the new 156kg DF90 weighs in much lighter than the 190kg DF90 it replaces. The old 90hp has been withdrawn from Suzuki’s range, replaced by a new 100hp motor.

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The new engines feature Suzuki’s unique offset driveshaft with two-stage gear reduction, which, amongst other advantages, gives them the ability to run larger propellers than is usual for engines in this size range.

On the water

Our venue for the first day’s run was Lyttelton Harbour. The weather was fine, but there was a biting wind to contend with, so we sought shelter behind Quail Island to conduct our performance runs. Speeds – measured on a handheld Garmin GPS – typically varied by at least 2mph (more at the top end of the rev range) depending on the wind and tide. Wherever practical, we made upwind/uptide and downwind runs.

The figures published are averages.

With less than an hour on the engines, we took things pretty easy to begin with, but by late afternoon we had sufficient time on the hour meters for a couple of full-throttle runs.

John Butler chose to fit the 90hp to a McLay 530 aluminium cuddy cabin boat, a basic model popular with anglers and one of Butler Marine’s best sellers. The well-proven hull will accept a range of horsepower up to 115hp, but performance was sparkling with the new DF90hp. Considering how well the boat went (see table), it’s certain that a Suzuki DF70hp would offer ample performance too, especially since the 70hp gives little away to its souped-up brothers in terms of torque and flexibility (even though maximum engine revolutions are 6000rpm for both the DF70 and the DF80, as opposed to 6300rpm for the new DF90).

The heavier fibreglass Reflex Chianti 485 sported the new Suzuki DF80. This boat is routinely fitted with much larger engines, so once again its performance with the 80hp was a revelation. It might have been a better fit for the DF90, but the 80hp proved willing and provided nearly 40mph performance – not bad for a family runabout. It’s likely that performance with the Suzuki 70hp would also be more than acceptable.

On the second day we towed the boats over the hill to Akaroa, where we explored the harbour and briefly ventured outside before the wind got up with a vengeance. We repeated our speed trials, concentrating on the Chianti, which was running a smaller 19-inch propeller for day two.

Overall performance was little different, but the boat-motor combo certainly felt better and response seemed crisper on day two. In fact, the Chianti-Suzuki DF80 pairing was a very happy one.

Both engines impressed with their urgency, emitting an appealing snarl as they came on song above 3500rpm. In both boats hole-shots were good, so skiing should not be a problem; the McLay reached 35mph in just 10 seconds from a standing start. Mid-range response is excellent.

The McLay was a real hot-rod. It seemed to appreciate the 90hp’s lighter weight on the transom and had no difficulty handling the horsepower and its attendant performance. The boat was nicely set up – an excellent match for the engine. Craig Archer, running the boat on his own, achieved a top speed of 45.9mph on a single run across the wind.

Both engines are admirably quiet and lack the heavy under-cowling sound insulation familiar from most outboards. Consequently, cowlings are light and easy to manage. Of the two boat-motor combinations, the Reflex probably offered the quieter and more refined boating experience, but the McLay-DF90 was definitely the most exciting.

We finished the day monitoring fuel flow for the Suzuki 90hp using an inline Fuelflow 2100 meter. We attempted to access the engine’s computer systems for definitive fuel-burn figures, but the engines are so new Suzuki’s diagnostics software doesn’t yet recognise them!

The flow meter hadn’t been calibrated, so the printed fuel flow figures are indicative only.

These engines are pre-production prototypes, so they may differ slightly when they reach showrooms later in the year, but judging by their performance and refinement on the water, there’s not much that needs changing. They’ll be a welcome addition to the Suzuki range.

Performance figures

DAY ONE
McLay 530-Suzuki DF90* Reflex Chianti 485-Suzuki DF80*
2000rpm: 6.6mph  2000rpm: 6.6mph
3000rpm: 18.0mph   3000rpm: 18mph
4000rpm: 27.0mph  4000rpm: 26.2mph
5000rpm: 35.5mph  5000rpm: 34.2mph
5800rpm: 43mph (WOT) 5650rpm: 38.2mph (WOT)
*Both engines running 21-inch propellers.

DAY TWO
Reflex Chianti
485-Suzuki DF80**
2000rpm: 6.2mph
3000rpm: 19.9mph
4000rpm: 24.6mph
5000rpm: 33.0mph
5800rpm: 39.1mph
**80hp running 19-inch propeller.

FUEL FLOW
McLay 530–Suzuki DF90
REVS SPEED FUEL FLOW
1000rpm 3.7mph 1.5lph
1500rpm 5.5mph 2.6lph
2000rpm 6.6mph 3.6lph
2500rpm 8.5mph 5.4lph
3000rpm 14.5mph 8.1lph
3500rpm 21.7mph 9.3lph
4000rpm 25.4mph 10.3lph
4500rpm 29.7mph 17.2lph
5000rpm No data No data
5500rpm 34.0mph 20.9lph
5800rpm (WOT) 41.0mph 28.2lph

All the tabled performance figures are averages measured over two or more runs with two adults and a single tote tank aboard, but little else. Fuel figures were taken on a single run across the wind (8-10kt) with three adults aboard.

John Eichelsheim, photos by Mike Hunter - October 2008

- Fishing News

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