Suzuki DF15

Weight buster, no lightweight

Suzuki was the second outboard manufacturer to release a four-stroke 15 on the Aussie market after Honda, with its 280cc BF15. Since then, Honda has released its 350cc BF15, de-rated from its BF20 counterpart, but Suzuki soldiers on with the original powerhead, which helps make the DF15 the lightest four-stroke 15 available.

The DF15 is 2.5kg lighter than the BF15 and between six and 7.7kg less than the Mariner, Mercury, Tohatsu and Yamaha competition. This allows the DF15 to be carried by one person, whereas (apart from the Honda) the competitors are really bolt-on engines. The lesser weight is also a plus when using the DF15 on conventional stem dinghies to 3.8 metres, whereas the competitors are better suited to V-nose punts which have shallower deadrises at the transom and subsequently more buoyancy aft.

Despite its age, the DF15 has similar features to the competition such as an upfront gearshift to suit freshwater anglers who troll extensively and compliance with Australian OEDA '3 Star' and California Air Resources Board (CARB) 2008 exhaust emission requirements.

Unlike the competition, the cooling water intake is located under the antiventilation plate and is to some extent self-cleaning in weedy waterways. However, Suzuki has still not fitted an external canister oil filter, although this is partially compensated by the replaceable oil cartridge, removed by undoing three screws. The oil sump has sufficient capacity to help absorb oil sludging when operated at trolling revs for extended periods, as four-stroke outboards suffer blowby at the piston rings unless run at WOT for a while after these periods.

Tested on a 3.7m V-nose aluminium punt and spinning the standard 10in pitch Suzuki alloy prop, the demo DF15 provided a good blend of performance and fuel efficiency with lower noise and vibration levels than some of the competition. The manual choke was a little antiquated compared to the automatic choke of the Tohatsu, but worked well. Cold starting required a firm two-hand pull. The engine warmed quickly and didn't blow any oil smoke, nor was there an oil smell backing upwind. When hot, only one hand was needed to fire up the engine.

Providing the antiventilation plate was kept immersed, power astern was good and no cooling water starvation occurred. The upfront gearshift was well positioned in relation to the tiller arm and twistgrip throttle, and overall the DF15 was very easy to use.

Unfortunately, my Bombardier Shoptach refused to pick up any engine revs (most likely due to the digital ignition system fitted) but judging from its acceleration and WOT performance, the engine was propped 'right' for our 340kg total including two adults and fishing tackle. It trolled quietly and smoothly (for a twin-cylinder four-stroke) at 3.7kmh using 0.4lt/h and planed at 20kmh, using the third trim position for an effective compromise between easy planing and reasonable WOT speeds. The WOT average was 45kmh and 6lt/h, and through a full-lock figure of eight turns at WOT, no prop ventilation occurred. There was none of the raspy exhaust note of Suzuki's two-stroke DT15 with the DF15 relatively unobtrusive, allowing us to talk normally.

Powerhead access is reasonable although access to the lower spark plug is 'tight'. Recommended servicing intervals are every 50 hours or six months after the 20-hour initial checkup when the valve clearances must be checked and head bolts tightened. The waterpump impeller should be replaced every 100 hours or yearly. The toothed camshaft belt should also be checked at this interval for any damage, but at least if it breaks, the engine is a non-interference type where the valves won't contact the piston crowns.

Although the DF15 is showing its age compared to the direct competition, it still remains a good alternative. It's economical to operate, is user-friendly and has proven to be a very reliable engine since its introduction. The warranty is two years for recreational usage.