Review: Mercury EFI F50 outboard

By: Andrew Norton

Presented by
  • Trade-A-Boat

There’s a reason why the Mercury EFI F50 is a classic four-stroke outboard.

Review: Mercury EFI F50 outboard
The Mercury EFI F50 outboard is the ideal power choice for tinnies from 4.5 to the 4.7m.

Unless you’re actively seeking a dose of tinnitus for your ears, opting for a four-stroke outboard motor when re-powering your aluminium runabout is a sensible choice. Midrange engines such as the Mercury F50 outboard have low vibration levels, much-reduced noise and excellent fuel economy over comparable two strokes.

So the Mercury EFI F50 has a lot going for it and since being de-rated from its F60 counterpart it’s way understressed. It was released on the Aussie market in September 2001, a year after the multi-carbie Mercury F50 was introduced.



The technology is a net result of a product-sharing arrangement with Yamaha. The OEDA 3 Star Mercury F50 develops 50hp at 5750rpm with a Wide Open Throttle range of 5500 to 6000rpm. The four-cylinder 995cc powerhead has a single overhead camshaft operating eight valves and is a non-interference engine, so no bent valves should the camshaft timing belt break — unlikely as it has designed lifespan of around 1000 hours.

Mercury put a lot of effort into designing the Mercury F50, such as employing a watercooled fuel system to prevent vapour lock on hot days, a problem that afflicted some carbie models. But like all current-model EFI car engines the EFI F50 starts instantly hot or cold as every engine should. The low pressure EFI uses standard automotive injectors and has an anti-knock facility for poor quality fuels but no oxygen sensor in the exhaust to advance the ignition timing when premium (95) unleaded is used. However, I recommend using this fuel because it’s better quality than standard (91) and has a longer shelf life that will stay fresher longer in underfloor fuel tanks.

The 18amp alternator has voltage regulation to prevent frying the starter battery on long runs and when mated with SmartCraft instrumentation the engine rpm will be automatically reduced should the engine overheat or suffer low oil pressure.

Powerhead access is okay with the fuel filter and canister oil filter easy to reach. The 2lt sump capacity absorbs most "sludging" between oil and filter changes and the recommended oil is Quicksilver FCW SAE 10W30, which is rated to over 40?C ambient temperature.

Mercury recommends servicing the F50 every 100 hours or annually after the first 20 hours but if you do a lot of trolling, changing the oil and filter every 50 hours will reduce oil dilution. Providing servicing is done by an authorised Mercury dealer the warranty for us recreational anglers is five years.

The Mercury F50 outboard motor has a dry weight of 112kg and a 1.83:1 gear ratio.



Mounted on an old 4.55m alloy runabout in combination with a 13in alloy prop, the demo Mercury F50 provided plenty of power and good holeshot performance for a two-adult load and total displacement of 680kg. Providing the antiventilation plate was kept immersed, power astern was good, great for backing off sandbars when fishing estuaries. Midrange torque was better than expected with a clean plane at reasonably low rpm and like most four stroke outboards the best cruising fuel efficiency was at 4000rpm, where also there was no prop ventilation through tight turns.

At or near WOT we could talk without raising our voices which my ears really appreciated. Damn all those carbie two-strokes I’ve reviewed over the years!

The Mercury F50 remains great value for tinnies to 4.7m, considering the engineering Mercury put into developing it. The salt water corrosion resistance is excellent and warranty backing unbeatable. Plus its quiet, effortless power delivery make it a nice engine to live with. And that’s before you even consider the costs of fuel saved over a carbie two-stroke!

As of November 2013 the longshaft remote control Mercury F50 had a price of around $8900 with a spare alloy prop for $400. Thanks to Tomos Marine, Marks Point NSW (02) 4945 3202 for supplying such a well set-up review engine. 



Average of two runs using SmartCraft instrumentation and handheld Lowrance GPS.

2.1kts (3.9kmh) @ 750rpm (trolling) – 0.7lt/h

12.9kts (24.0kmh) @ 3300rpm (clean plane) – 5.9lt/h

18.0kts (33.4kmh) @ 4000rpm (cruise) – 7.3lt/h

25.9kts (48.0kmh) @ 5000rpm (max cruise) – 10.6lt/h

30.7kts (56.9kmh) @ 5800rpm (WOT) – 17.5lt/h




Honda BF50D

Suzuki DF50A

Yamaha F50F





Cyl / HP / Rpm

3 / 49.3 / 5750

3 / 49.3 / 5800

4 / 49.3 / 5500













OEDA stars




* Uprated from 40 HP.


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Originally published in TrailerBoat #302, December 2013.


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