Review: 2017 Yamaha F90B Four-Stroke Marine Outboard

When Yamaha invited us up to have a look at the latest  F90B four-stroke I wasn’t all that enthusiastic to pry myself from my desk but when they mentioned that the F90B was all-new and would set the standard for fuel consumption and bring the war on weight to Mercury and Suzuki, I knew I had to go. Luckily for you – and me – Yamaha put on a thoroughly good show with three hulls ready and waiting for testing.

The F90B has more in common with F115B than any of the three models it replaces, yet it takes a different approach to how it puts power through the prop. While the lower leg, block, cylinders and pistons come from the F115B, the head has been simplified with a single overhead camshaft, though still with four valves per cylinder. Using the already light F115B block and running the more simple head helps the F90B come in as light as 162kg for a 20-inch 'L' leg, 10kg lighter than the out going F90A but still a few kilos off the DF90A from Suzuki. The engines it replaces – the F80A, F90A and F100A – are all heavier and more complicated, yet smaller in displacement.

On the water we tested the F90B on a Quintrex 490 Cruiseabout, a bowrider-style aluminium hull we at Trade-a-Boat are familiar with. With three on board we verified Yamaha’s claims for fuel consumption, achieving as much as 3km per litre at a comfortable 35km/h and 3500rpm cruise. What stood out most was the lack of noise at cruising speeds as well as starting and when engaging gear.

Yamaha’s Shift Dampening System (SDS), which softens gear engagement dramatically, makes it onto the F90B. It’s a fantastic system and makes other outboards feels clunky and rough.

One of the test boats, a Bar Crusher 535C had a 25inch 'XL' leg.

Starting is smooth and fuss-free, while at idle the engine is barely noticeable. Most impressive, however, was the quiet at cruise. Conversation barely above normal volume was effortless while running at 30km/h, something rare among outboards mounted to alloy hulls. Thinking it could have been the hull’s design dampening the noise, we jumped onto a Stabicraft 1600 Carbon Fisher and a Bar Crusher 535C, two more alloy hulls. The noise on board was again exceptionally low at speed.

Thanks to its 1832cc block, the F90B has a lot of low-down grunt. An enlarged 60mm throttlebody allows large volumes of air into the combustion chamber almost instantly, delivering great throttle response – punching the throttle from low speeds or even at cruise, the engine responded without delay, pushing the hull onwards with ease.

No doubt we will see an extension of the technology employed in the F90B in other horsepower ratings and – hopefully – in other engine categories. The results of the refocusing and simplification of the engine prove the old adage Keep It Simple Stupid works as well as ever.

F90B Key Technology

Variable trolling

A great function that allows revs to be raised or lowered by 50rpm increments between 600-1000rpm. Yamaha released a new standalone switch for it, too.

High-output alternator

More and more important for high-power electronics, the F90B’s alternator cranks out as much as 28amp at idle and a high 35A from 3000rpm onwards.

YDC30 marine alloy

Exclusive to Yamaha, YDC30 was launched in the 90s and is a specific alloy mix designed to reduce corrosion and lengthen the lifespan of the motor.

Offset crankshaft

The F90B’s crankshaft design is offset 5mm from the centre of the cylinder for a more efficient transfer of power to the crankshaft.

Y-COP

Remote lock your outboard through Yamaha Customer Outboard Protection. Much like an immobiliser in your car, Y-COP renders your outboard dead without the programmed fob.

SPECIFICATIONS

YAMAHA F90B

RRP FROM A$14,199 (plus rigging)

TYPE Inline four-cylinder fuel-injected four-stroke petrol outboard

RATED HP 90

DISPLACEMENT 1832cc

WEIGHT 162kg (F90LB)

LEG LENGTH 20 inch

GEAR RATIO 2.15:1

PROPELLER Alloy 13.25x16in three-blade GP

ALTERNATOR OUTPUT 35A

EMMISSION RATING 3-star

Sea Trials 

2017 Yamaha F90B Fourstroke fitted to a Qunitrex 490 Cruiseabout

90hp Yamaha F90B Fourstroke enginewith three on board, 70L fuel and running an alloy 13.25x16in three-blade GP propeller.

600rpm reaches a speed of 2.59kt with fuel burn of 1.3L/hr and economy of 1.99nm/L

3500rpm reaches a cruising speed of 18.49kt with fuel burn of 10.4L/hr and economy of 1.78nm/L

5900rpm (WOT) reaches a maximum speed of 34.58kt with fuel burn of 37.35L/hr and economy of 0.93nm/L

* Sea-trial data supplied by Yamaha, verified by Author.

Yamaha F90B v Mercury 90hp FourStroke

Comparing the F90B and Qunitrex 490 package against main rival, the Mercury 90hp FourStroke on a Stacer 509

The F90B’s main competition, the Mercury 90hp FourStroke, has been out since 2015. It takes a similar approach to making power and keeping weight down – big cubic capacity four-cylinder with single overhead cam. Handily, we have extensive data on a very similar hull from our own testing in the same waterways.

The F90B is 10 per cent better on fuel at optimal cruise but the Mercury was pushing its hull, a Stacer 509, 6kt (11km/h) faster. Flat out, the Yamaha claws the Mercury back in, delivering a top speed of 37.35kt (70km/h) but burning more fuel – 37.5L/h to the Merc’s 36.2kt (67km/h) and 32.6L/h.

Comparing the data further, we found that at 4000rpm the Yamaha is still more efficient than the Mercury at its best and is a lot closer in speed, only 2kt off but an impressive seven per cent better on fuel.