Review: Tohatsu M5B outboard motor long-term evaluation

By: Andrew Norton

The Tohatsu M5B portable outboard motor proves that no one makes small marine engines quite like the Japanese.

Review: Tohatsu M5B outboard motor long-term evaluation
The Tohatsu M5B portable outboard motor will take spare parts from Mercury dealers.

Since September 2007 I’ve had the joy of using a 1996 Tohatsu M5B portable outboard motor owned by my fishing partner Di. The engine previously had a hard life on the NSW Central Coast, made abundantly clear by the corrosion areas on the leg and engine pan.

From 2012 to 2014 the portable Tohatsu M5B outboard was run only in a flushing drum a couple of times and seemed to overheat each time, so it was stored until I could have the cooling water impeller checked. But in August 2014 the engine didn’t overheat, so the next day I took it for a run on Di’s 1979 3.6m Savage Funfish. After about five minutes the flow from the pilot water discharge was back to normal and testing could commence on the Nulon semi-synthetic outboard oil I was already using in my 2005 Tohatsu M8B. For whatever reason, the blockage had cleared.

Over the next three months the water flow was fine and the engine delivered full power, while averaging only 0.9lt/h on the Funfish and my early seventies 3.4m Mk1 Savage Gull and 2003 Sea Jay 3.4 Punt.

This got me thinking about why would I buy a Chinese clone of the Tohatsu M5B portable outboard motor when I could have the real thing? A quick check of YouTube showed horror stories about failures in Chinese outboards, with no spares backup. Sure the Chinese clone might be up to 40 per cent cheaper to buy, but would it still be running 18 years later with no failures? Don’t get me wrong, from my testing of these for an importer, the Chinese make some damned good power equipment such as line trimmers and portable generators, but I want to know an outboard will always get me home!


Tohatsu M5B

Released on the Australian market in 1985, the loopcharged Tohatsu M5B portable outboard motor develops a full 5 brake horsepower (bhp) and has also formed the basis of the Mercury 5M with only minor changes, such as a more rounded upper cowl. It has CD ignition with electronic timing advance and a full gearshift, 360-degree steering with automatic reverse lock, six trim positions and one shallow-water drive setting. There’s provision for connecting a 12lt plastic remote fuel tank in addition to the 2.5lt integral tank and a 5amp 12V unregulated alternator is optional.

A carry handle on the front of the lower pan makes carrying the Tohatsu M5B outboard motor very easy, and the spark plug and disposable fuel filter are easily reached. Lakeside Marine, the national Tohatsu distributor, recommends servicing the M5B every 50 hours or annually, and providing this is done by an authorised dealer the recreational warranty is three years.


On the water

Swinging the standard 8in pitch semi-weedless alloy prop, Di’s portable Tohatsu M5B outboard motor performs best on the flat bottomed Sea Jay punt and can plane a two-adult load and stay planing at less than wide open throttle. Like all single-cylinder outboards the M5B is very sensitive to hull loading, but being a two-stroke it can run for extended periods near WOT without powerhead damage.

Di’s engine always starts first pull hot or cold, though is better suited to strong all-welded hulls having plenty of transverse framing, such as the Sea Jay. When trolling, it effectively massages tiller arm flab, smoothing out above 2000rpm to prevent the finger and arm numbing that occurs with some four-stroke singles at higher rpm. But when working hard it’s anything but quiet as my long-time co-tester Richard Ardizzone and I found out when conducting noise testing using a decibel meter. During trials the total displacement for the Sea Jay was 285kg, the maximum I recommend for the M5B.

Using premium unleaded (95 RON) and Nulon oil at 50:1 the M5B blows some oil smoke only on cold start-up, but can troll for at least 15 minutes without a single bubble of smoke in its wake. The spark plug remains spotlessly clean on this fuel/oil combination.


The Trade-a-Boat verdict

Call me simple but there are few things more enjoyable than fishing from a small tinny with a good mate (preferably female, because they always catch fish) and powered by a little outboard, be it two or four-stroke.

In my opinion the M5B is one of the best-value outboards I’ve ever tested. It’s cheap to run and maintain, performs well on the right hull and like all Tohatsu outboards I’ve long-term tested over the past 32 years is incredibly reliable. And if you’re touring remote parts of Aus, spares are available from Mercury dealers, making the Tohatsu M5B portable outboard engine even better value.

For your nearest Tohatsu dealer, visit


Tohatsu M5B portable outboard sea trials

Single 5hp Tohatsu M5B outboard motor. Average of two-way runs across measured distance, calm water, using inline fuel-flow gear, portable tachometer and handheld dB meter





1100 (trolling)




2000 (low flab reduction)




4900 (plane and cruise)




5200 (WOT)




Averaging 4kts, 10 per cent WOT and 20 per cent trolling




2.3 per 2.5lt tank; 11 per 12lt tank

* With 20 per cent reserve both tanks. Sea-trial data supplied by the author.


Tohatsu M5B specs

Tohatsu M5B price: $A1387

As of November 2014

TYPE Single-cylinder two-stroke petrol outboard motor


REC. RPM RANGE 4500 to 5500


BORE X STROKE 55 x 43mm

WEIGHT 20kg (dry, short shaft)


WARRANTY 3 years



Competing outboards


Mercury 5M

Yamaha 5C








1 / 5 / 5000

1 / 5 / 5000





5 years

 3 years

OEDA Stars





See the full version of this review in Trade-A-Boat #257, September 2015. Why not subscribe today?

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