The power of one

Released in August, the TLDI 115 is now Tohatsu’s most powerful direct injection two-stroke outboard and is the de-rated version of the upcoming TLDI 135.

In comparison, the Mariner and Mercury Optimax 115 is up-rated from its 90 and 75hp counterparts and has hardly the torque of the Tohatsu, which amongst DFI engines is matched only by the Evinrude E-TEC 115. But although the E-TEC 115, along with the Optimax 115, meets CARB 2008 ‘three-star’ exhaust emission regulations, they don’t match up in terms of fuel efficiency.

Considering its piston displacement, which is 16 per cent greater than the Optimax 115 and two per cent over the E-TEC 115, the TLDI 115 is very fuel efficient. Mounted on a 5.05m Signature 520C Cuddy Cabin, spinning a 16-inch pitch stainless steel Power Tech prop and pushing a total of 950kg, the demo TLDI 115 easily outperformed the TLDI 90 on the same hull and returned better fuel efficiency than the E-TEC 115.

Trolling at a steady 700rpm, it averaged 4.6km/h using 0.8lt/h and achieved a clean plane at

30.6km/h and 3000rpm using 13lt/h. Cruising effortlessly at 4000rpm, it averaged 47km/h and 19.6lt/h and, through full-lock figure of eight turns at these revs there was no prop ventilation. With the throttle lever floored at 4000rpm, the tacho leapt instantly to 5700rpm and the acceleration threw us back in our seats, with the last 150rpm being reached only a few seconds later.

At a fast cruise of 60.3km/h and 5000rpm, the Tohatsu used 29.2lt/h and, at wide open throttle, the averages were 68.9km/h and 38.4lt/h at 5850rpm. On this hull, pushing 920kg and spinning a 15-inch Power Tech prop, the TLDI 90 averaged 40.9km/h at 4000rpm and used 12.8lt/h, increasing to 27.6lt/h at WOT, where the averages were 58.9km/h and 5600rpm.

The next stage of my testing of the TLDI 115 will be on a Mako 560 Centre Console. This will allow me to compare the engine directly with the Optimax 115 and E-TEC 115 – so far tried only on aluminium hulls – as well as the Suzuki DF115 and Yamaha F115A. But as a rough guide to fuel consumption, on a Stacer 565 Coral Master runabout displacing a total of 1000kg, an Optimax 115 averaged 44.4km/h and 17.6lt/h at 4000rpm, and 64.9km/h and 37.6lt/h at WOT and 5500rpm.

On a TABS 5.0 Marquis Bowrider displacing 1150kg, an E-TEC 115 averaged 45.1km/h and 26.4lt/h at 4000rpm, and 64.4km/h and 45.9lt/h at WOT and the same revs.

The demo TLDI 115 had only a few hours on the clock and was still running on a break-in fuel/oil mix, resulting in a slight oily smell when backing upwind, although no oil smoke was visible at any time. The engine started instantly hot or cold and quickly settled down to a steady 700rpm in or out of gear, with the idle revs adjustable to 800 or 900rpm by simply pushing in the ignition key for a second at a time – ideal for setting the right trolling revs.

Vibration levels at 700rpm were on par with the V4 E-TEC 115 and significantly lower than the three-cylinder Optimax 115. Across the entire rev range the TLDI 115 was slightly quieter than either of the direct competition engines.

The throttle/gearshift overlap was precise and, providing the anti-ventilation plate was kept three quarters immersed, power astern was good.

Maintaining the TLDI 115 appears straightforward. Servicing intervals are 50 hours or six months after the initial 10-hour checkup. There is a three-year warranty for recreational usage.