Big things in small packages

When I tested Tohatsu's single-cylinder MFS6A a couple of years ago, I found it both more powerful and fuel efficient than its de-rated MFS5A counterpart. But having tested Suzuki's single-cylinder four-stroke 6hp in January this year, it appears, in my opinion, that Suzuki has beaten Tohatsu in the power-to-weight and performance stakes.

UPGRADED
Uprated from its smaller DF4 and DF5 counterparts, the DF6 was released late last year. The attractive little engine also runs remarkably clean, meeting the US EPA 2006 and California Air Resources Board (CARB) 2004 requirements for exhaust emissions. It has an overhead valve powerhead with gear-driven camshaft and pressure lubrication, a rev limiter (6000rpm), and the option of an alternator that starts charging at only 2200rpm. That's a handy feature if you plan to run a portable depthsounder or electric motor on your dinghy for dead silent trolling and manoeuvring around snag piles. It's great to be able to keep a deep-cycle battery charged up and ready to go when you need it.

Other user-friendly features include a full gearshift lever (F/N/R) and 180° steering for greater manoeuvrability in tight places. One full tilt position and two shallow-water drive settings, which engage automatically as the motor is tilted, are also standard features. There's also provision for permanently bolting the motor to a transom and all necessary hardware is provided as standard.

The exhaust relief is located directly beneath the powerhead, eliminating any back pressure when the motor leg is well immersed. This can sometimes happen when reversing a small tiller-steer dinghy where most of the weight is in the back, pushing the leg deeper into the water.

An easily replaced anode is fitted to the leg as well as atop the anti-ventilation plate where its condition can be quickly checked.

UNDER THE COWL
Unlike the MFS6A, the DF6 has an integral fuel tank, a real advantage for small cartopper punts and dinghies where space is at a premium, but if needed, there's the optional 12lt plastic remote tank. The fuel connector is compatible with the old OMC and recent Bombardier fuel lines. An oil level sight glass in the lower cowl allows the oil level to be checked without removing the upper cowl to access the dipstick.

HANDLING & ERGONOMICS
Angled slightly to port, the tiller arm is attached to the steering pivot tube reducing steering effort and placing the twistgrip throttle further forward for better comfort while underway. But the biggest improvement over the Tohatsu is a large carry handle at the back of the motor, enabling it to be easily carried cylinder-up without fear of sump oil flooding the cylinder. It's a wonder more manufacturers don't follow suit on their portable engines. They are cumbersome things to lug around.

Supplied by Haines Suzuki Marine through my local Mercury/Suzuki dealer Hamiltons Marine of Mayfield, NSW, the demonstration motor was operated on Quicksilver SAE 10W30 oil.

RELIABILITY
Providing the motor was stored upright before being used, no oil smoke appeared at any time and starting required only one hand hot or cold. The motor warmed quickly from cold and had the lowest vibration levels of any single-cylinder four-stroke above 4hp I've tested so far. Power astern was excellent and with the anti-ventilation plate kept immersed no cooling water starvation occurred. However, the pilot water discharge "telltale" should be angled to starboard for easier checking.

The demonstration motor was mounted on a 3m de Havilland John 10 punt (similar to Hunter Marine's Fisherman 10) and carried two adults and fishing tackle, displacing a total of 235kg.

PERFORMANCE & ECONOMY
Spinning the standard 7in prop, at Dead Slow Troll, the Suzy averaged 3.6kmh on 1240rpm using 0.18lt/h and returned exactly the same fuel efficiency as the MFS6A. Whereas the Tohatsu needed 5000rpm to plane the punt, the Suzy did this at 4800rpm and cruised effortlessly at 5100rpm averaging 26.8kmh and 2.0lt/h compared to only 20.4kmh and 1.8lt/h.

Only at wide open throttle did the Suzy lose out for fuel efficiency, averaging 29.2kmh at 5830rpm and using 2.4lt/h whereas the Tohatsu averaged 28.4kmh on 5740rpm and consumed 2.1lt/h.

The biggest surprise was across my standard 7.5kmh "loop" with 10% wide open throttle operation and 40% dead slow troll operation, where the Suzy averaged only 0.60lt/h compared to 0.72lt/h for the Tohatsu. Over this loop, the DF6 had a fuel/oil ratio of 960:1, excellent for a water-cooled four-stroke with this percentage of wide open throttle operation.

ACCESS & MAINTENANCE
Powerhead access is very good and the upper and lower cowls have solid-colour mouldings to reduce the unsightly appearance of scratches that occur with sprayed-colour cowls and can easily happen when an outboard is carried in the boot of a car.

Recommend servicing intervals are every 50 hours or six months after the first 20 hours with waterpump impeller replacement every 100 hours or once a year.

After 50 hours of saltwater leg/lower unit immersion, no corrosion was apparent anywhere on the loan motor.

CONCLUSION
Haines Suzuki Marine offers a comprehensive two-year warranty for recreational applications.

Operators of small aluminium dinghies and tenders looking for a quiet, vibration-free, extremely economical little engine that still packs a mean punch would do well to check out the Suzuki DF6 four-stroke.