Yamaha 30D

Yamaha's coming of age

Released on the Aussie market in 1986 following the success of the three-cylinder 40 and 50, the 30D was the first three-cylinder 30 available. For a while it had to compete with Suzuki's three-cylinder DT30C, another innovative engine, but when Suzuki outboards were discontinued locally in 1999 this engine disappeared. All the carbie two-stroke Suzukis currently imported by The Haines Group have twin-cylinder premix powerheads.

When first released, apart from the three cylinders, what really separated the 30D from the competition was the multipoint oil injection available even in manual start models. Yamaha's "Precision Blend" varies the fuel/oil ratios from around 200:1 when trolling, up to 80:1 or 50:1 depending on the model, unlike the 100:1 to 50:1 of Mariner and Mercury outboards, and 120:1 to 50:1 of Tohatsus. This enables Yamahas to run very cleanly for a carbie two-stroke and dramatically reduces oil costs in everyday usage.

Unfortunately, the manual start oil injection model was discontinued in the late nineties, leaving 100:1 for manual start engines and oil injection, and power trim and tilt for the electric start model.

I first tested a 30D in 1986 on Yamaha's W23 longboat with a "soft tail" transom similar to the UB670. Even with four adults aboard, the engine had no trouble planing this load and, having three-cylinders, was beautifully smooth-running for its output.

Seven years later, I borrowed a 30D for three months' evaluation on a Sea Al Seaman 4.5 aluminium dinghy equipped with a flat floor. Despite having a manual choke system (40/50 models have cold-start fuel primers), it normally started first pull hot or cold, with no more effort needed than a twin-cylinder 20, warmed quickly in the cold winter test months and would troll for hours at 670 revs without missing a beat. The only operating drawback was a slight "flat spot" on transition from the idle to main carbie jets, a common problem with the 30D.

Spinning a standard 13-inch pitch alloy prop and pushing a total of 460kg, including two adults and fishing tackle, the loan engine trolled us at 4.3kmh using 1.1lt/h and, despite running 50:1 in the fuel in addition to the oil injection, oil smoke appeared only after 30 minutes of trolling. When operating on the shallow-water drive position, power astern was good and no cooling water starvation occurred, providing the antiventilation plate was kept immersed.

The 30D planed us at around 20kmh and cruising at two-thirds throttle or 4400rpm, averaged 45.5kmh using 10.1lt/h. Through full-lock figure of eight turns at these revs no prop ventilation occurred despite the Seaman's full-length keel. The Wide Open Throttle average was 56.3kmh at 5520rpm using 13.3lt/h and, at these revs, we could still talk normally, so quiet was the engine.

When we carried another adult aboard, bringing the displacement to 550kg, the WOT average was 51.0kmh at 5000rpm.

Even allowing for the undercowl oil tank the loan 30D had very good powerhead access with the spark plugs, triple carbies and ignition advance linkages easily reached. The premix model would be even easier to work on, and a nice touch is the zinc anode in the powerhead cooling water passages, in addition to the anode under the antiventilation plate.

Recommended servicing intervals are every 50 hours or six months after the initial 10-hour checkup. The waterpump impeller should be replaced every 100 hours or yearly.

The 30D is rated 1 Star under the Australian OEDA exhaust emission star ratings and has a two-year warranty for recreational applications. It's still rated the number one choice by anglers who troll a lot without wanting to opt for more expensive and complex four-strokes in this power range.