Yamaha 40V Outboard Motor Review

Originally published in TrailerBoat #267, March / April 2011.

Back in the early ’80s, Yamaha Motor was constantly upgrading its three-cylinder two-stroke outboard range from premix to oil-injection. Released on the Aussie market in 1985, the Yamaha 40V was a part of these changes.

YAMAHA 40V

The 40V was unusual in that most of the competition of the time had twin-cylinder powerheads. Yamaha reasoned that by using the exhaust gas pulses from one cylinder to scavenge the next it would create a more fuel efficient and lower emission engine. The Yamaha 40V outboard motor was also available with “Precision Blend” variable ratio oil-injection in electric-start models.

Precision Blend differs from the Mercury Marine and Tohatsu competition in that oil is injected at the reed valves by a crankshaft-driven pump. The oil bypasses the carbies, eliminating the need to run these dry or use stabilising additives to prevent the oil from separating from the petrol and clogging the carbie jets. The system is far more precise than Mercury’s and Tohatsu’s single-point oil-injection, where oil is mixed at the fuel pump. This means the fuel/oil ratios on the Yamaha are far leaner, particularly when trolling.

The only real drawback of Yamaha’s system was that it could suffer oil “gelling” if different types of oil were mixed together. However, this is unlikely to occur if one brand of oil is used for the life of the engine. Based on my long-term evaluation of oil-injected two-stroke Yamaha outboard motors in the past, Yamalube 2 oil would be my choice.

LOWER EMISSIONS

The Yamaha 40V outboard motor is more fuel efficient than its twin-cylinder single carbie Yamaha 40X (CV) counterpart and has significantly lower emissions. For an additional ten per cent higher weight the 40V has oil-injection compared to a 100:1 premix — useful in a boat with an underfloor fuel tank. Being a de-rated Yamaha 50, the 40V also has a less-stressed powerhead despite its one per cent smaller piston displacement.

Other advantages include a cold-start fuel primer in electric-start models for instant cold starting compared to electric choke systems and full voltage regulation to prevent “frying” the starter battery on long runs to and from a favourite fishing spot. Both engines have standard wide-range power trim and tilt.

ON THE WATER

The review Yamaha 40V was mounted on a Savage 435 Bay Cruiser spinning a 12in pitch Yamaha alloy prop and pushing 600kg including two adults. This was the maximum rated power for this aluminium runabout.

Starting instantly hot or cold, the 40V blew oil smoke only on cold starting. Providing the antiventilation plate was kept at least three quarters immersed, power astern was good and no cooling water starvation occurred.

The standard side-mount Yamaha remote control box had smooth and positive shifting into forward or reverse gear. When trolling, the noise and vibration levels were much lower than 40X models I’ve tested in the past and only at or near wide open throttle did the 40V become relatively noisy due to carbie induction roar.

Powerhead access is not quite as good as the 40X due to the undercowl oil tank and three carbies but is still reasonable with the spark plugs, fuel/oil filters and carbie linkages easily reached. All wiring is colour-coded and neatly laid out as expected in a Yamaha outboard. After the 10-hour initial checkup, servicing is required only every 100 hours or annually. This also applies to waterpump impeller replacement.

Providing the 40V is serviced by an authorised Yamaha dealer the recreational-usage warranty is three years. You can pick one up for the recommended retail price of $6780. Spare alloy props  will cost you $130.

YAMAHA 40V PERFORMANCE

COMPETING ENGINES