Yamaha 30D engine test

By: Andrew Norton


Yamaha’s enduring 30D is a true legend of its two-stroke range…

Yamaha 30D engine test
Yamaha 30D engine test

Back in 1986, Yamaha released the world’s first three-cylinder two-stroke 30. This followed on from the success of its more powerful three-cylinder engines, starting with the 75 introduced to the Kiwi market in late 1982.

Known as the 30D, Yamaha’s new 496cc 30 had features such as a three-carbie, loop-charged powerhead and variable-ratio oil injection. Yet at 61kg for the manual-start longshaft version, it was only 17 per cent heavier than the popular twin-cylinder cross-flow 521cc Johnson 30, which weighed 52kg. The 30D developed 29.6hp at 5000rpm while the Johnson developed 30hp at 5500rpm.

As with Yamaha’s 40V released a year earlier, the 30D used exhaust gases from one cylinder to scavenge the next, making it far more fuel efficient than a big twin. It also had "Precision Blend" oil injection, where the oil was injected at the reed valves, with a fuel / oil ratio that varied from 80:1 at WOT (wide open throttle) way down to 200:1 when trolling.

The only competition to the 30D has been Suzuki’s oil-injected, three-cylinder DT30C, an innovative engine that idled on two cylinders. But this engine was discontinued in the local market in 1999. Both before and since the DT30C, the 30D has had the market to itself.

Unfortunately you’ll only find oil injection in the electric-start version of the 30D (the 30DETOL), which also has power trim and tilt. Manual start versions make do with a fixed 100:1 fuel / oil premix (after the initial 10-hour break-in period on a ratio of 25:1).

Whereas the larger three-cylinder Yammies have cold-start fuel primer systems, the 30D has a manual choke. In any case, because of the inherent balance of this engine, it’s remarkably easy to start.

On the water

Since 1986 I’ve spent a fair amount of time using 30D engines. Although they’ve enjoyed modifications and improvements over the years they have remained the benchmark in this class.

I recall one instance where I found myself powered by a 30D aboard a 7m Yamaha 23 workboat — a boat that planed easily with three guys aboard. In another instance, which I’ll detail here, I was on a 4.5m Seaman aluminium dinghy, which turned out to be a great little working runabout and superb harbour fishing boat.

After carefully running in the Seaman’s new engine for 10 hours, it was subjected to extensive testing over a three-month period. Particularly impressive was the remarkably low level of vibration when trolling at the minimum of 670rpm, although I have to say it was also quiet across the entire rev range, and even at WOT — where the roar of carbie induction often creates quite a racket.

Through tight figure-of-eight turns at 4000rpm there was no hint of prop ventilation, despite the Seaman’s long keel. There’s no doubting the fact that Yamaha makes excellent alloy props!

For the performance trials the Seaman was loaded with two adults and fishing tackle, bringing the total displacement to 460kg. Cold starting required a firm two-handed pull, while only one hand was needed when the engine was hot. Only when running on the break-in mix did the engine blow any oil smoke, and even then this only occurred when the engine was cold.

The upfront gearshift was easy to use and, providing the anti-ventilation plate remained immersed, power astern was good when operating on shallow-water drive, with no adverse effect on the engine’s cooling system.

The only real operating problem encountered during the loan period was a "flat spot" on transition from the idle jet to the main carbie jets when the throttle was opened quickly. According to engine owners I’ve interviewed, this has been a common problem, but it doesn’t occur when the throttle is opened gradually. No amount of tuning seems to resolve the issue.

The manual-start 30D I borrowed had oil injection, but the 0.9lt undercowl oil tank didn’t take up much space on the powerhead and even with a starter motor fitted, the engine would still be easy to service. Whichever model is chosen, there’s easy access to the spark plugs and carbie / throttle linkages (the 30D has mechanical ignition timing advance).

Yamaha recommends servicing the 30D every 100 running hours, or annually after the first service at 20 hours.

The wrap

Since its release the 30D has developed a reputation for reliability and survival in salt water, particularly since Yamaha’s YDC30 alloy was introduced in the ’90s. It provides saltwater anglers with affordable, reasonably fuel efficient, easily maintained and smooth-running power, and I think the 30D will be around for a good while yet. As of April 2011, a manual longshaft 30D sets you back $5354, while the electric-start version costs about $8000.

Performance

2.3kts (4.3kmh) at 670rpm (trolling) using 1.1lt/h
22.5kts (41.7kmh) at 4000rpm (cruising) using 6.9lt/h
30.3kts (56.3kmh) at 5520rpm (WOT, two adults) using 13.3lt/h
27.5kts (51.0kmh) at 5000rpm (WOT, three adults) using 13.5lt/h

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