Suzuki DF2 engine test

By: Andrew Norton


After five years in the field, Suzuki’s DF2.5 is still unbeatable in its power range

Suzuki DF2 engine test
Suzuki DF2 engine test

Suzuki first released its smallest four-stroke outboard, the DF2.5, back in January 2006. Developed to compete directly with Honda’s BF2D, which was released locally in 1998, the DF2.5 took a completely different path to providing owners of small tenders with a compact, low-emission and fuel-efficient outboard.

Instead of a 57cc OHV air-cooled powerhead driving the prop via a centrifugal clutch, Suzuki opted for a 68cc OHV thermostatically controlled water-cooled powerhead driving through a conventional dog clutch to give neutral and forward.

Suzuki also fitted a pressure lubrication system to enable a wider range of oils to be used, whereas the splash lubrication system of the BF2D required a SAE 10W30 oil that provided adequate lubrication only to 32°C of ambient temperature. Despite these differences the DF2.5 weighed in at only 13.0kg.

In all other aspects the designs were very similar. Four trim positions and an automatic tilt-lock were provided; the tiller arm with motorcycle-type twist-grip throttle could be folded down alongside the outboard leg, and because the recoil starter-cord passed through the upper cowl this could only be partially removed from the lower cowl.

Like the Honda, the DF2.5 was designed specifically for a transom height of only 15in, not 16-plus like the Mariner/Mercury F2.5, Tohatsu MFS2.5A and Yamaha F2.5A competition, which are way too heavy for their outputs. This means the DF2.5 should only be used on hulls having no more than 15in from the transom crown to the hull bottom.

On the water

I borrowed a new DF2.5 from Haines Suzuki Marine to compare directly with a BF2D that I’d been testing for eight years. During that time the unit clocked up 90.6 hours on a total of four very different hulls. The best of these were a 3m flat-bottomed aluminium de Havilland John 10 Punt and a 2.95m Walker Bay 10 polyethylene dinghy.

On the John 10 punt, spinning the standard 5.4in pitch weedless prop and pushing a total of 225kg (including two adults and fishing tackle) the DF2.5 averaged 2.3kts (4.3km/h) at trolling rpm using 0.1L/h; at wide open throttle (WOT) it did 5.8kts (10.9km/h) using 0.9L/h. In comparison, the BF2D averaged 5.6kts (10.5km/h) at WOT using 0.93L/h and pushing the same load.

For testing on the Walker Bay we swapped the standard prop for a 4.5in prop. Pushing a total of 270kg, including the two of us, the average speed at half throttle was 5.0kts (9.3km/h) doing 4400rpm. At WOT it was 5.6kts (10.4km/h) and 5400rpm. By comparison, the Honda on this hull averaged 4.9kts (9.1km/h) and 5.4kts (10.0km/h) respectively at these rev rates.

Around a "loop" of normal cruising with 10 percent WOT and 40 percent trolling operation, the DF2.5 used 0.45L/h on both hulls, averaging 4.4kts (7.5km/h).

Since I’ve started testing it the DF2.5 has only used Quicksilver SAE 10W30 oil. This is a FCW (Four Cycle Watercooled) oil designed specifically for water-cooled engines that can provide adequate lubrication to over 40°C of ambient temperature. As a general note, you should never change the brand and type of oil used on a four-stroke engine.

I note that Suzuki needs to pay closer attention to paint adherence. Despite having only 99 hours of saltwater leg/lower unit immersion there was extensive paint blistering at the leg/lower unit join. Compare this to the BF2D’s paintwork, which is still in very good condition after 700 hours of immersion.

The wrap

Servicing the DF2.5 is straightforward, with recommended intervals of every 100 hours or six months after the initial check-up at 20 hours or one month. As no external canister oil filter is fitted I would change the oil every 50 hours, especially if the engine has been used for extended trolling periods between changes.

Overall the DF2.5 has provided a lot of fishing pleasure for very little cost. It is a far more user-friendly engine than the direct two-stroke competition consisting of direct-drive engines. The recreational-usage warranty is two years. As of June 2011 the DF2.5 costs around $1356.

Performance

On a de Havilland John 10 punt weighing 225kg with a 5.4in prop
2.3kts (4.3km/h) using 0.1L/h (trolling)
5.5kts (10.3km/h) using 0.9L/h (WOT)

On a Walker Bay 10 weighing 270kg with a 4.5in prop
5.0kts (9.3km/h) @ 4400rpm (half throttle)
5.6kts 10.4km/h @ 5400rpm (WOT)

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