Suzuki DF175
Suzuki's DF175 is real competition to DFI two-strokes, reports Andrew Norton
Suzi's big four
The DF175 has all the features of the 150 including Suzuki's offset driveshaft, watercooled voltage regulators for twin-battery charging, chain driven camshafts and twin counter rotating balance shafts, but differs in that a continuously variable intake valve timing system is fitted. This system is also fitted to the Suzuki DF250 and DF300 and differs from Honda's VTEC in that it actuates from 1500rpm upwards instead of 4500rpm for the BF150 and BF225.
The engine breathes better across most of its rpm range and unlike the Hondas, there's no surge in the upper rpm-range, resulting in overall performance approaching that of a similar-output DFI two-stroke.
THE COMPARISONS
Up until I tested a DF175, every Seafarer Victory 6.0 I had previously tried was powered by a DFI two-stroke, whether it be a Ficht, E-TEC or OptiMax, so the demo rig supplied by The Haines Group made for a very interesting comparison.
Increasing the rpm to 2000 returned 12.4kmh and 8.0lt/h compared to 13.0kmh and 8.3lt/h for the OptiMax. A clean plane was achieved at 30.6kmh and 3200rpm whereas the OptiMax planed us at 29.7kmh but the same rpm. Spinning a 21in prop and pushing a total of 1.7 tonnes an E-TEC 225 on a Victory planed us at 32.2kmh and 2600rpm.
Cruising effortlessly at 4000rpm the DF175-powered hull averaged 44.5kmh and used 25.6lt/h compared to 48.1kmh and 25.7lt/h for the OptiMax and 61.2kmh and 37.1lt/h for the E-TEC. The lower speed at these rpm was to be expected as the DF175 develops maximum power around 1000rpm higher than the DFI two-strokes.
Through full lock figure of eight turns at 4000rpm the DF175's prop refused to ventilate. Surprisingly for a continuously variable valve timing system, there was a rapid increase in rpm when the throttle lever was floored from 4000rpm with acceleration out to Wide Open Throttle as good as the OptiMax.
At WOT and 5050rpm the OptiMax-powered Victory averaged 65.8kmh and 57.9lt/h, while at WOT and 5500rpm the E-TEC-powered hull averaged 96.6kmh and 75.7lt/h. The Suzy at WOT was much quieter than the OptiMax and E-TEC and despite having four cylinders compared to six, the vibration levels were comparable.
NO OIL SMELLS
The DF175 started instantly hot or cold and didn't blow any oil smoke, but unlike the OptiMax and E-TEC there was no oil smell when backing upwind. Providing the antiventilation plate was kept at least three-quarters immersed power astern was good. The Suzuki remote control box had a positive shifting action into ahead or astern gear.
Powerhead access is very good with the oil sump dipstick and filler cap easily reached.
The combined Hydrocarbon (HC), Oxides of Nitrogen (NOX) and Carbon Monoxide (CO) emissions are 171.9 gm/kW/h, slightly lower than the OptiMax 150 but higher than the OptiMax 175 and E-TEC 225. However, as the DF175 has lower HC + NOX emissions than the OptiMax 150 and 175 it gains an OEDA 3 Star rating whereas the latter pair are rated 2 Star. The warranty is five years for recreational usage, and long, extra long and extra long counter rotation models are available.
| SPECIFICATIONS |
| SUZUKI DF175 |
| Engine type: Crossflow DOHC four-stroke |
| Cylinders/valves: Four inline/16 |
| Prop HP at rpm: 172.9 at 5800 |
| WOT rpm range: 5500 to 6100 |
| Piston displacement (cc): 2867 |
| Bore x stroke (mm): 97 x 97 |
| Ignition system: CD w/ electronic timing advance |
| Charging circuit (amps): 44 w/voltage regulation |
| Break-in period (hrs): 10 |
| Fuel delivery: Multipoint EFI |
| Fuel type: ULP 91 or 95 RON |
| Fuel capacity: Portable tank not supplied |
| Oil type: Suzuki SAE 10W40 |
| Oil capacity: 8.0lt |
| Gear ratio: 2.50:1 overall |
| Transom heights (in): 20/25 |
| Weights (kg): 215/220 |
| Rec. retail prices: $23,830/$24,131 |
| Spare S/S prop: $1000 |
| Servicing costs* |
| Year One: $484 |
| Year two, etc: $308 |
