Yamaha 25NMHL outboard review

I loved the ’80s: big hair, power dressing, going on Perfect Match for an all-expenses paid weekend away. And I didn’t have to colour my hair or tint my eyebrows.

This magnificent decade was also when Yamaha’s 25NMHL was born. In 1988, to be specific. All 25hp outboard motors had single-carbies and most were equipped with side gearshifts, but following the success of its 30D Yamaha released a compact twin-carbie 25hp with up-front shift. Outboard Marine Corporation’s domination of the 25hp market was threatened.

YAMAHA 25NMHL

Why was the Yamaha 25NMHL outboard motor such a challenge to the Johnson 25? Well, most readers know that one carbie per cylinder is more efficient than one carbie for two cylinders because the air / fuel mix doesn’t “puddle” at the reed valves. Twin carbies enabled Yamaha to opt for a smaller piston displacement, reducing bulk while improving top-end performance with better combustion chamber “breathing”. Add the 100:1 fuel / oil mix (after 10 hours on 25:1) and a fuel-efficient engine was created.

The OEDA one-star-rated 395cc loopcharged powerhead develops 24.7hp at 5500rpm with a WOT range of 5000-6000rpm. There’s an optional 6A alternator that doesn’t have voltage regulation so it may fry a battery for electronic toys.

The outboard motor has a dry longshaft weight of 49kg and gear ratio of 2.08:1, and the 24L plastic fuel tank supplies plenty of juice for a day’s angling.

Powerhead access is excellent, with spark plugs and fuel filter easily accessed. Yamaha recommends servicing the Yamaha 25NMHL every 100 hours or annually after the first 20. If a semi-synthetic oil such as is used the engine can be run on premium unleaded (95 octane) with amazing reductions in oil smoke and spark-plug fouling. There’s a three-year warranty for amateur anglers.

PERFORMANCE ON THE WATER

When creating the Yamaha 25NMHL outboard motor, Yamaha thoughtfully considered the, let’s say increased girth, epidemic among male anglers and designed the powerhead to shake when trolling. The vibration travels from the tiller through the operator’s arm and into the body, giving a good toning. It’s like an outboard and gym machine rolled into one. But to make sure the vibration won’t overdo flab reduction, it reduces substantially above 2000rpm.

On a 4.2m Clark Pro Punt, the demo Yamaha 25NMHL run on 100:1 and only blew smoke on cold starting and after 30 minutes or more of trolling. It needed a firm two-hand pull when cold.

The 25 warmed quickly in the cold, power astern was good and no cooling water starvation occurred with the anti-ventilation plate kept immersed when using the shallow-water drive setting. The up-front shift was logical to use compared to the side shifts of the Japanese competition.

Swinging a 13in alloy prop and pushing 390kg, the Yamaha 25NMHL outboard motor was well matched to this bulky vee-noser and planed at about one-third throttle opening. There was no prop ventilation through tight turns at two-thirds throttle, or 4000rpm, but at WOT the engine was a bit raucous due to carbie induction roar.

With a mix of cruising, trolling and WOT runs, the Yamaha 25 engine averaged 4L/h with up to six hours from the standard fuel tank.

THE TRADE-A-BOAT VERDICT

The 25 years since its Aussie release have gone quickly, but the Yamaha 25NMHL outboard motor has proved a reliable engine with great saltwater corrosion resistance.

Sure, other 25s may be cheaper and have longer warranties, but the Yammie’s performance makes it a fun outboard to drive without costing a fortune. It can also be fitted with remote control and forward steering.

As of May 2013 the manual longshaft version of the Yamaha 25NMHL price was $3730, with a spare alloy propeller going for around $180.

Thanks to Yamaha Motor Australia, Murarrie, Queensland (07 3906 7041), for the loan of the Yamaha 25NMHL for this review.

YAMAHA 25NMHL PERFORMANCE

2kts (3.7kmh) @ 800rpm (trolling) – 1L/h

10.5kts (19.4kmh) @ 3400rpm (min. plane) – 5.1L/h

15.4kts (28.6kmh) @ 4000rpm (cruise) – 6.6L/h

25.7kts (47.7kmh) @ 5700rpm (WOT) – 12L/h

THE COMPETITION

Originally published in TrailerBoat #296, June/July 2013