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Yamaha's F40F is ideal for midrange top-ender tinnies.

Yamaha F40F/F40LA

Hard to believe this engine has been around for ten years. During this time it’s clocked up an impressive reputation for reliability and everyone I’ve spoken to has had nothing but praise for this engine.

The combination of three cylinders combined with multipoint EFI and a beautifully-designed tiller arm have made this engine virtually unbeatable in its power range. The engineering is classic marine four-stroke and the excellent saltwater corrosion resistance has really set this engine apart from the others.


By having one piston up and two down, the F40F or F40LA as it’s recently been renamed overcomes inherent balancing issues found in twin-cylinder four-strokes, just like the balancing piston found in Yamaha’s old twin-cylinder F25A. Sure the balance ain’t quite as good as a four-cylinder engine where two pistons are up and two down, but having four cylinders in this power range just adds weight without a considerable reduction in vibration. And because the pistons and con rods are the same as in the F25A and four-cylinder F60C, securing spare parts in remote regions should never be an issue.

Switching from three carbies to EFI in 2008 eliminated the need to carefully balance the carbies, a tedious task due to the need for vacuum gauges and setting carbie linkages to perfection. This effort was needed to prevent the engine running like a dog, as did all multi-carbie four-strokes when they went out of tune.

As with all of Yamaha’s single overhead cam engines the clearances for the six valves are adjusted using a spanner and feeler gauge, a task that any competent marine technician can do. The use of two valves per cylinder means the engine is a non-interference type, where should the timing belt break the valves won’t contact the piston crowns. Though in reality timing belts breaking are rare providing they’re inspected annually and replaced every 1000 running hours.

The ignition system includes a rev limiter and flywheel alternator pumps out up to 15amp and has voltage regulation so it won’t fry the starter battery on long runs to and from a favourite fishing spot. A laptop computer with dedicated software can be quickly connected to diagnose any running faults with the engine management system.

At two litres the oil sump has sufficient capacity to absorb oil dilution that occurs during extended trolling periods when there is blow-by past the piston rings. The oil filter is easily replaced and recommended oil is Yamaha’s own 4M, though other FCW (Four Cycle Water cooled) SAE 10W30 oils can be used.

Because the F40F/F40LA doesn’t have an oxygen sensor in the exhaust, opting for premium (95) won’t advance the ignition timing as it does in one of the direct competition. However, because there is less likelihood of having fuel tainted with ethanol, I’d choose premium over regular (91) every time. Just be prepared for higher vapour loss from an underfloor fuel tank with a topsides breather than when using regular, because the additives package added to regular unleaded to raise the octane level evaporate quicker. Included is a water separating fuel filter mounted remotely from the engine and essential with EFI systems as water can do a lot of damage to injectors.

Yamaha really knows what owners of tiller-steer top-ender tinnies want in a tiller arm and the F40F/F40LA has in my opinion a masterpiece of design. The arm incorporates an upfront gear shift, ignition key switch, twist-grip throttle friction adjuster and a trim/tilt button that stays in the same plane regardless of the twist-grip throttle angle. Also trolling rpm can be adjusted in increments of 50rpm from 650 to 900, giving more choice of trolling speeds than the direct competition.

A nice touch is the freshwater flush system that operates without running the engine, and great for  those who don’t want to disturb neighbours. However, I’d still occasionally attach muffs to the lower unit and run it for 10 or so minutes to clear salt (actually aluminium chloride) deposits from the cooling passages, thermostat and around the impeller.

Servicing intervals are every 100 hours or annually after the first 20 hours or three months and the recreational-usage warranty is four years.


The Blue Fin Viking 4.5 supplied as a test bed for the demo F40F was a perfect match and the 12in alloy prop allowed the engine to rev well out as all Japanese four-strokes like to do. The F40F started instantly with no oil smoke, nor any oil smell backing upwind. The engine warmed quickly from cold, though I recommend a minimum three minutes warm-up in neutral to allow lubricating oil to fully reach the cam bearings. The upfront shift gave brilliant control and providing the anti-ventilation plate was kept immersed, no cooling water starvation occurred and power astern was good.

Sensibly the outboard was not fitted with a hydrofoil to increase stern lift when operating a tiller steer tinny one-up. If you’re going to operate a boat this way just stow three or four plastic 20-litre jerry cans full of water forward to create better fore and aft hull trim. Hydrofoils are just a stupid invention and attaching one to the anti-ventilation plate instantly voids the engine manufacturer’s warranty. The long tiller arm helped isolate my tiller arm from the engine, but only at low rpm was there any vibration which felt like a slight tremor, unlike carbie two-strokes in this power range.

Holeshot was progressive, if not stunning, with a clean plane at lower speeds than imagined. It was quiet across the rpm range and the power trim acted quickly to trim the leg in or out according to whether travelling upwind or down. Through tight turns at 4000rpm there was no prop ventilation, but what surprised me was how far out the leg could be trimmed before prop blow out. Hard to believe we were running an alloy prop!


It’s been 33 years since the first Yamaha four-stroke outboard (the F9.9) was released here and since then the corporation has applied typical Japanese thoroughness in its design and engineering in the F40F/F40AL and other four-stroke outboards. The attention to detail is excellent and with a little TLC (such as running in the engine according to Yamaha’s recommendations) and regular maintenance the F40F/F40AL should return a long service life. Just don’t expect it to reduce body or tiller arm flab!


Single Yamaha F40F/F40LA on 4.5m Blue Fin Viking tinny swinging a 12in alloy prop and pushing a total of 600kg including two adults and test equipment. Average of two-way runs on Lake Macquarie NSW, calm water. Range is in nautical miles from the standard 24lt plastic remote fuel tank with a ten per cent reserve.

750 (trolling) 2.6 0.6 94
3500 (clean plane) 11.1 4.6 52
4000 (cruise) 14.6 5.5 57*
5000 (max cruise) 21.7 8.8 53
5800 (WOT) 26.0 12.6 45

*Best planing fuel efficiency. Sea-trial data supplied by the author.


Type Three-cylinder four-stroke EFI outboard

Rated BHP/MHP* 39.4/40 at 5500rpm

WOT rpm range 5000 to 6000

Displacement 747cc

Bore x stroke 65 x 75mm

Gear ratio 2:1

weight 99kg dry, long shaft

RRP $8380

OEDA stars 3

*Brake horsepower/metric horsepower or PS

Check out the full review in issue #503 of Trade-a-Boat magazine. Subscribe today for all the latest boat news, reviews and travel inspiration.


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