words - Andrew Norton
Andrew Norton puts four new Suzuki four-strokes through their paces at the company's product launch on the Gold Coast
Perfect weather set the mood for the Haines Group media day held at Couran Cove on the Gold Coast in October. The Haines Group used this idyllic location to showcase its new Suzuki DF150/175, DF25 and DF2.5 outboards, plus the new Signature 580BR, 600C and 770C hulls, along with the Haines Traveler TC165.

Also made available for testing were a range of Kevlacats from 5.2 to 9.0m and Powercats ranging from the 2400 Cab to the 3400 Custom Partycat. Aluminium hulls included the Horizon 415 Angler, Joshua Boats five-metre Centre Console, Tabs 5.7m Marquis Bowrider, Fisher 660 Maxi Series and Australian Master Marine 3300 Tournament. And for the tiny DF2.5, a Redback RIB from Swift Marine was the baby of the fleet.

All boats I tried were set up to perfection and sufficient time was allocated to give the boats and engines a good workout on the Gold Coast Broadwater.

Undoubtedly the stars of the event were the new engines, all of which are innovative in their respective power ranges and all comply with California Air Resources Board (CARB) 2008 exhaust emission regulations.

Engine type Crossflow OHV single cylinder
Valves/drive Two/gear
HP @ revs 2.4 @ 5500
WOT rev range 5250–5750
Piston displacement (cc) 68
Ignition system CD
Fuel delivery Single carburettor
Fuel capacity 1.0lt integral tank
Gear ratio 2.15:1
Prop (in) 7.4 x 5.4
Weight 13.0kg
Rec. retail $1100

Developed to compete directly with Honda's 57cc BF2D, the DF2.5 is Suzuki's smallest and lightest four-stroke outboard, weighing two per cent more than the Honda and 20 per cent more than the 55cc two-stroke Suzuki DT2.2.

 Yet the DF2.5 has plenty of user-friendly features. The water-cooled powerhead enables it to be operated safely in tropical climates, and low viscosity engine oil is needed for the splash lubrication. A forward-neutral gearshift with 360 degree steering is fitted and powerhead access is much better than its main competition.

Access to the rocker cover for valve clearance adjustment is excellent and because the cylinder is canted well to port, there's little fear of sump oil entering the cylinder when the engine is laid on its side in a car boot.

As with the Honda, there's an oil level sight glass in the lower cowl but sensibly Suzuki has fitted a large carry handle to the back of this ensuring the DF2.5 will always be carried the right way up.

On a three-metre Redback RIB, pushing a two-adult load and spinning the standard prop, the demo DF2.5 clearly had ample power, particularly at low revs. Starting easily hot or cold, it didn't blow any oil smoke. While vibration levels were comparable with the Honda, noise levels were low, making it a pleasant engine to use over long distances. However, having to check the exhaust relief hole with a finger while underway to ensure the waterpump impeller was working was a pain and Suzuki really should fit the same easily-visible pilot water discharge as used in the DF4 to DF6 range of engines.

The simple twist-grip throttle and stainless steel gear lever worked well. At Wide Open Throttle in the confines of Couran Cove's harbour we averaged 10kmh and cruised at about eight at half throttle. The DF2.5 would really suit small displacement rowing dinghies such as the Walker Bay 10 or Canadian canoes to five metres.

Engine type Crossflow 70 degree V-twin
Valves/drive Four/chain
HP @ revs 24.7 @ 5000
WOT rev range 4700–5300
Piston displacement (cc) 538
Ignition system CD with electronic timing advance
Charging circuit (amps) 6/15
Fuel delivery Single carburettor
Gear ratio 2.09:1
Prop (in) 10.25 x 12 alloy
Shortshaft manual start weight 69kg
Longshaft electric start weight 76kg
RRP Prices available January 2006

The DF25 is the world's first V-twin outboard and was developed to be a lighter alternative to the three-cylinder DF25, de-rated from its DF30 counterpart. The new DF25 is 26 per cent lighter than the model it replaces yet has only ten per cent less piston displacement.

 Suzuki Motor Corporation opted for the V-block configuration to reduce vibration levels to that of an inline twin without needing a counter-balancing shaft or the counter-balancing piston of Yamaha's F25A, needed in twin-cylinder four-strokes above 400cc. The 70 degree angle between the cylinders was regarded as the maximum without significantly increasing powerhead bulk and allowed for Suzuki's proven chain-driven camshaft to be fitted, improving powerhead reliability. The V-block layout positions the powerhead further forward to aid manual tilting and setting of shallow water drive, while the OHV design simplifies valve clearance adjustments.

Suzuki also opted for a single carburettor (which supplies air/fuel mix to the cylinders via a Y-shaped intake manifold) to reducing servicing complexity but fitted a wax-pellet automatic choke to improve cold-starting ease. An upfront gearshift and lever-type steering friction adjuster are fitted, although electric start models lose the manual overhead recoil starter, and the 1.5lt engine oil sump has half the capacity of the old DF25.

On a Horizon 415 Angler dinghy, pushing a two-adult load and spinning a 12in alloy prop, the demo DF25 had similar noise and vibration levels to Yamaha's F25A tested on a similar hull, but had better bottom-end torque. Cold or hot, the engine started instantly and didn't blow any oil smoke. Apart from a flat spot on transition from the carbie idle to main jets it accelerated smoothly right out to WOT. The DF25 planed at 22.0kmh on 3700 and cruised at 25.3kmh on 4000 revs, although some prop ventilation occurred through full-lock figure of eight turns at these revs. The WOT average was 38.2kmh on 5200 revs and due to the V-block layout the engine didn't seem to revving as hard as it was, resulting in us being able to hold a normal conversation.

SUZUKI DF150/175
Now the largest displacement four-cylinder four-stroke outboards currently available in their power bracket, the Suzuki DF150 and DF175 outboards have innovations not found in the direct competition.

Both models have a sequential multipoint EFI 2.9lt DOHC powerhead with chain-driven camshafts and twin counter-rotating balance shafts for reliability over belt-driven camshafts, according to Suzuki. Both engines have Multi Stage Induction to vary the length the intake manifold airflow has to travel, increasing bottom-end torque and improving top-end 'breathing'.

All Suzuki DFs 90–250hp have offset driveshafts to position more of the engine over the transom for improved fore and aft hull trim and two-stage gear reductions. The larger reduction allows for coarser-pitch props to be used without increasing gearcase torpedo diameter and hydrodynamic drag. Both engines have alternators fitted with isolating diodes to charge both the starter and house batteries and 80 per cent of maximum output is available at only 1000rpm. A rubber mounting system reduces transmitted vibration from the engines at all revs.

 On a Signature 600C, pushing three adults and spinning a 21in pitch stainless-steel prop, the demo DF150 planed at 22.0kmh on 3000rpm and cruised effortlessly at 40.5kmh on 4000rpm through to 52.0kmh on 5000rpm. WOT average was 58.5kmh on 5500rpm and through full-lock figure eights at 4000rpm, no prop ventilation occurred. The DF150 was, to my mind, much quieter than its OptiMax 150 competition.

The DF175 gains its 17 per cent power increase at only another 300 revs over the 150 through the use of variable valve timing on the intake valves, the same system used in the DF250. Bottom-end torque is dramatically improved.

On a Kevlacat 7.2, pushing a four adult load and spinning 21in stainless steel props, the twin DF175s fitted planed the boat at 26.0kmh on 3000rpm and cruised effortlessly at 42.2kmh on 4000 revs through to 57.5kmh on 5000. The WOT average was 72.3kmh on 6000 revs and again through full-lock figure eight turns at 4000 revs, no prop ventilation occurred. The quietness of the twins under the hardtop was a real advantage over comparable DFI two-stroke engines.

Engine type Crossflow DOHC four-cylinder
Valves/drive 16/chain
HP @ revs - DF150 147.5 @ 5500
HP @ revs - DF175 172.9 @ 5800
WOT rev ranges - DF150 5000–6000
WOT rev ranges - DF175 5500–6100
Piston displacement (cc) 2867
Ignition system Electronic engine management
Charging circuit (amps) 44 w/ voltage regulation
Fuel delivery Sequential multipoint EFI
Final gear reduction 2.5:1
Props (in) 14.75 x 21 stainless steel
Longshaft weight 211kg
Extra long weight 215kg
Rec. retail - DF150 $19,260/$19,670
Rec. retail - DF175 $20,845/$21,107

Published : Thursday, 1 December 2005

Prices and specifications supplied are for the market in Australia only and were correct at time of first publication. makes no warranty as to the accuracy of specifications or prices. Please check with manufacturer or local dealer for current pricing and specifications.

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