Mariner/Mercury Super 15 outboard: 10 years on

By: Andrew Norton

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  • Trade-A-Boat

The Mercury Marine Super 15 outboard is still a success story, 10 years after its introduction.

Mariner/Mercury Super 15 outboard: 10 years on
The Super 15 outboard has its origins in commercial engines, being based on the Tohatsu M18E2.

Originally published in TrailerBoat #257, June 2010

The Mariner/Mercury Super 15 has been an incredibly popular model since its release over a decade ago because it offered anglers a great combination of value for money and sound engineering features.

According to my local Mariner and Mercury dealers, sales of the Super 15 have made up about 50 per cent of 15hp two-stroke outboards sold. The dealers told me anglers wanting a reasonably priced 15hp engine usually opt for the Super 15, while anglers after a lighter weight and more features, like a combined throttle/gearshift system, buy the US-built Mariner/Mercury 15.



Based on the Tohatsu M18E2 engine, the Super 15 has a commercial heritage. It features rod-operated throttle linkages, a stop button located on the lower cowl for greater reliability, and an auxiliary cooling water-intake under the antiventilation plate. In addition to the trim tab zinc, anodes are fitted to the transom brackets and steering pivot-tube.

As with all other two-stroke Tohatsu outboards under 40hp, it has a side-mounted gearshift, but at least the six trim positions provide fine trimming of leg-angle relative to the transom rake. One shallow-water drive setting is provided, and there’s also a full tilt-lock. The reverse lock-lever must be flipped down to set shallow-water drive or full tilt, and this may confuse some operators. A Super 18, basically a re-badged M18E2, is also available in overseas markets.

The biggest difference between the Super 15 and its crossflow 262cc US counterpart is the emission levels. The Super 15 has an OEDA "1 Star" rating, making it one of the cleanest-running carbie two-strokes in its power range, with combined hydrocarbon and oxides of nitrogen emissions of 173.5g per kW/h, and carbon monoxide emissions of 270.3. The US 15’s emissions are 323.2 and 533.4g per kW/h, with increases of 86 and 97 per cent, giving it an OEDA "0 Star" rating.

Another difference is the power output. The Super 15 develops 15.3hp at only 5125rpm compared to 15.0hp at 5500rpm for the US model. In fact, the Super 15 is the most powerful carbie two-stroke 15 on the Aussie market, which makes it more suitable for tinnies to 3.8m compared to the competition.



When I first reviewed the Super 15 in 2000 it hadn’t been in the market for long. Since then I’ve tested five of these engines and all have proved to be excellent performers for their output.

The first Super 15 outboard I tested was mounted on a Bermuda 375 Dolphin dinghy. Spinning the standard 8.8in alloy prop it provided excellent performance on this bulky hull. Pushing a total of 320kg including two adults and test equipment, it trolled us at 2.9kmh (1.6kts) at 800rpm, using 0.8lt/h. Vibration levels at this rev rate were much higher than the US 15, which used the same amount of fuel when trolling, but on a 3.6m tinny weighing 285kg in total.

The Super 15 outboard motor planed the Dolphin at only 18.7kmh (10.1kts) and 3500rpm and cruised quietly at 25.0kmh (13.5kts) at 4000rpm, using 4.1lt/h. No prop ventilation occurred through full-lock figure-of-eight turns at this rev rate.

The WOT averages were 37.7kmh (20.3kts) and 5590rpm drinking 7.6lt/h, while the US 15 used 8.0lt/h on the 3.6m tinny. However, at WOT the Super 15 was noisier than the US 15 and had substantially higher vibration levels.

Late last year I tested a Super 15 outboard on a 3.5m Kiwi-built polyethylene SmartWave 3500, which is rated to 25hp and absorbed most of the engine vibration. Spinning the 8.8in prop and pushing a total of 350kg including two adults, the 15 planed us at only 18.6kmh (10kts) at 3500rpm. It cruised at 23.2kmh (12.5kts) at 4000rpm using 4.1lt/h. The WOT averages were 36.0kmh (19.4kts) and 5500rpm using 7.6lt/h. Mariner/Mercury Super 15


Engine type

Loop-charged premix two-stroke outboard motor


Two, in-line

Prop HP at rpm

15.3 at 5125

WOT rpm range

4750 to 5500

Piston displacement


Bore x stroke

60 x 52mm

Ignition system

CD w/mechanical timing advance

Charging circuit

 6amp w/o voltage regulation

Break-in period

10hrs on 25:1

Fuel type

ULP 91 RON minimum

Fuel capacity

25lt plastic remote tank

Oil type

TC-W3 Quicksilver Premium

Fuel/oil ratio


Gear ratio


Transom height




Rec. shortshaft retail price


Spare alloy propeller price


Servicing costs*

Year one $303; Year two etc. $180

* As per manufacturer’s recommended schedule excluding parts. All prices current as of April 2010. Demo engines and prop and servicing prices from Lifestyle Marine, Toronto, NSW, phone (02) 4959 1444; and Tomo’s Marine, Marks Point, NSW, phone (02) 4945 3202.


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Originally published in TrailerBoat #257, June 2010


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