REVIEW: Chinese made Aqualine 5 Four Stroke Outboard

THE NITTY GRITTY OR SHOULD THAT BE COPYCAT?

Unlike its 3.5, Aqualine has really raided the parts bin for the 5. The power head is straight from the two-stroke Tohatsu M4C/M5B and the leg and lower unit from Yamaha’s old four-stroke F4A. In Tohatsu guise the big single has tons of mid-range torque to get a small punt out of the hole but not much bottom-end grunt, but it’s the opposite with the Aqualine 5. The F4A has a long steering pivot tube to transfer engine vibration from the boat to the tiller arm, giving constant flab reduction to the tiller arm above fast idle.

By using the same lower unit as the F4A Aqualine 5 owners can either use a flushing drum or muffs after saltwater use. However, although the same eight-inch pitch alloy prop is used, it has a shear pin instead of spline drive and is attached to the prop shaft with not only a cotter pin but also a castellated nut through which the cotter pin passes. Very reasuring though not so good for reducing hydrodynamic drag.

As standard the 5 is fitted with a massive three-litre integral fuel tank plus a 12-litre plastic remote unit or tote tank as some call it. Tightening the cylinder head bolts requires removal of the integral tank, which has a fuel outlet screen to make up for the absence of a disposable in-line fuel filter. The remote tank has a removable screen in the filler cap but frankly a conventional filter in the fuel lines would be better and shouldnt be too hard to add. 

Apart from the integral tank overhanging the cylinder head the layout is almost identical to the Tohatsu M4C/M5B. Unlike on the 3.5 the carbie has idle and main jets with a conventional push-pull choke knob, while the ignition has electronic timing advance. Sensibly, the engine cowl has a rubber ring around its base to prevent chips when it’s removed and placed on a rough surface.

Providing the three-month check-up is performed by the selling dealer the recreational usage warranty is two years. The fuel/oil ratio is 50:1 after the first two hours on 25:1.

ON THE WATER

Spinning the standard eight-inch prop and pushing a two-adult plus fishing tackle load, the loan 5 got my 2003 Sea Jay 3.4 Punt to semi-planing speeds but because the torque fell off above 4000rpm the 5 was incapable of planing this hull, unlike the Mercury 5M and Tohatsu M5B which ran out to 13.8kt under identical test conditions spinning an eight-inch prop, though admittedly with a deeper gear ratio of 2.15:1. To reduce engine weight on the transom the remote fuel tank was used at all times. 

The 5 started easily hot or cold with little more effort needed than the 3.5. However, due to the absence of the exhaust relief fitted to the Mercury and Tohatsu models to reduce back pressure at low revs, the Aqualine 5 would not idle for any length of time and ran better from upwards of one-quarter throttle opening.

Interestingly, at one-quarter throttle it was faster than the 3.5 at wide-open throttle and used less fuel, resulting in the same fuel consumption around my cruising test loop. The pilot water discharge or tell-tale had the strongest flow I’ve ever seen from a 5, even when operating on the lowest shallow water drive setting, where power astern was still very good.

However, because of the above-prop exhaust – the Mercury and Tohatsu 5s have through-prop exhausts – the Aqualine was noisier at or near WOT. Across the rev range vibration through the tiller arm was also much higher and I could just feel my left arm flab melting away. Another example of Chinese manufacturers value-adding!

Being able to use either a flushing drum or muffs is very handy. In the drum I found that running the 5 at fast idle in reverse prevented water being ejected from the drum and loaded up the engine sufficiently to reach normal operating temperature and clear out aluminium chloride deposits (commonly mistaken for salt) in the cooling water passages. Unusually, the engine also reached operating temperature on the muffs after about 10 minutes so I would use this method in preference to a drum because it’s quicker to set up and uses less water.

THE WRAP

If you’re after a 5 that will plane a small flat-bottomed punt then the Mercury and Tohatsu 5s are the way to go. But if pushing heavier loads while plodding around at displacement speed is your preference, the Aqualine 5 is a viable alternative to mainstream brands. It’s also substantially cheaper.

The loan engine will be re-tested with a seven-inch prop to see if we can get the Sea Jay out of the hole. The results of this testing will be published down the track along with the next loan engine – a four-stroke 2.5.

SEA TRIALS

Single Aqualine 5 on Sea Jay 3.4 Punt, 8in prop, total displacement 285kg, including two adults and fishing tackle. Average of two-way runs on Lake Macquarie, NSW, calm water, using fuel flow gear and portable high-tension lead tachometer. Range is in nautical miles from the 12L fuel tank with a 10 per cent reserve.

2500rpm reaches a speed of 5.4kt with fuel burn of 0.9L/hr and economy of 0.17nm/L for a range of 65nm, producing 81.6dB at 3m

3200rpm reaches a speed of 6.1kt with fuel burn of 1.4L/hr and economy of 0.23nm/L for a range of 47nm, producing 82.8dB at 3m

4700rpm (WOT) reaches a maximum speed of 7.9kt with fuel burn of 2.4L/hr and economy of 0.30nm/L for a range of 36nm, producing 90dB at 3m

Loop of cruising including 10per cent WOT, averaging 4.0kt = 1.0Lt/h

QUICK SPECS

Engine type Single-cylinder loop-charged premix two-stroke outboard

Rated BHP/MHP* 5.0/5.0 claimed at 5000rpm

WOT range 4500 - 5500rpm

Piston displacement 102cc

Bore x stroke 55 x 43 mm

Gear ratio 2.08:1

Dry weight 20kg

RRP A$995

OEDA stars 1 (estimated)

*Brake horsepower/metric horsepower or PS