Review: Tohatsu MFS 20C outboard motor

By: Andrew Norton

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  • Trade-A-Boat

The Tohatsu MFS 20C is a far sweeter engine package than its predecessor, the 18B.

Review: Tohatsu MFS 20C outboard motor
At under five grand, the Tohatsu MFS 20C outboard motor has many improvements over its predecessor.


Originally published in TrailerBoat #266, February / March 2011.

In some ways, the Tohatsu MFS 20C, a 20hp four-stroke outboard released on the Aussie market a while back, is a simpler engine than its MFS 18B predecessor. For example, the automatic choke has been replaced by a simple manual choke. By increasing the cylinder bore by 2mm, the engine has a seven per cent greater piston displacement but its weight is unchanged, at 52kg.

To achieve the 11 per cent greater output over the 18B, the wide open throttle rev range is up from 5000 to 6000rpm, to 5400 to 6100rpm, with the rev limiter still set at 6250rpm. Automatic rev reduction is set to 2000rpm should the oil pressure drop below the required minimum level.



For the first time in a Tohatsu under 25hp, the MFS 20C is available with optional power trim/tilt, which adds only about 4kg to the overall weight. Tohatsu has also fitted decompression starting, which raises the exhaust valves slightly during the initial turning-over of the engine.

Sensibly, Tohatsu has retained the voltage-regulated alternator from the 18B, which prevents "frying" of the starter battery on long runs to and from a favourite fishing spot.

Tohatsu has also retained the lower unit from the 18B, ensuring parts commonality, handy when you’re touring remote regions. Essentially the same lower unit as fitted to Tohatsu’s two-stroke M18E2, but with a deeper gear ratio, it has an auxiliary cooling water inlet under the anti-ventilation plate. This ensures that some water reaches the powerhead should the main cooling intakes above the gearcase torpedo get blocked.


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Lakeside Marine, the national Tohatsu distributor, provided me with a run-in review Tohatsu MFS 20C to test on a Makocraft 390 Estuary Tracker Open. The 390 had a sizeable 2m beam carried well aft and its transom easily handled the additional weight of a four-stroke over a two-stroke of comparable output. After a series of initial tests, Lakeside’s Dave Denny fitted a 10in pitch Tohatsu alloy prop to suit the total weight of 400kg, which included Dave, myself and testing equipment.

The Tohatsu MFS 20C was much easier to start than the 18B demo engine I’d previously tested and required only a light one-handed pull. Surprisingly, the starting effort needed was much less than the 294cc M18E2, and after a few minutes the 20C was fully warmed up. Using standard ULP and Valvoline SAE 10W40 oil, there was never any oil smoke, while overall vibration levels were substantially lower than those of the demo 18B.

However, like the Tohatsu 18B (and M18E2), the reverse lock lever must be flipped-down to fully tilt the engine, or set to shallow water drive for easier operation Tohatsu should the reverse the lock lever.



The Tohatsu MFS 20C was set on the third trim hole (of six) to provide the best compromise between easy planing and a reasonable WOT speed, resulting in good overall performance.

Trolling at 800rpm it averaged 2.1kts (3.9kmh) and 0.4lt/h while planing was achieved at 9.2kts (17.2kmh) doing 4300rpm. The minimum cruising speed was 4500rpm, where the averages were 11.8kts (22.0kmh) and 3.6lt/h, but opening the throttle to 5000rpm returned 14.8kts (27.5kmh) and 3.8lt/h. No prop ventilation occurred through full-lock, figure-of-eight turns at 5000rpm.

The WOT averages were 19.6kts (36.3kmh) and 5.9lt/h at 6000rpm, where we could still talk normally, and with lower levels of vibration than the 18B at WOT.

Powerhead access is excellent, with the oil sump dipstick, oil filler cap and canister-type oil filter all easily reached. Lakeside Marine recommends servicing the MFS 20C every 50 hours or six months after the initial 10-hour checkup. The waterpump impeller should be changed every 100 hours.

Saltwater corrosion resistance should be good too, as the 20C has bonding wires from the lower unit, with its trim tab anode right up to the transom brackets. Another anode is fitted to the bottom of the transom brackets.



Compared to the M18E2 the Tohatsu MFS 20C’s emissions are 37 per cent less, and it comes with a recreational-use-only, three-year warranty. With a recommended retail price of $4114 (longshaft), Tohatsu’s latest engine offering has plenty to offer recreational boaties.




Yamaha F20B (long-shaft model)




53.7kg (manual start)


4 years




Originally published in TrailerBoat #266, February / March 2011. Why not subscribe today?


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