MERCURY

words - Andrew Norton
Mercury's OptiMax 200 is a beautifully under-stressed engine, reports Andrew Norton

Big tinny's mate

The least powerful of a trio of Direct Fuel Injection two-strokes from 200 to 250hp, the OptiMax 200 produces substantially more torque than its 2.5lt OptiMax 175 counterpart and is well suited to powering maxi-trailerable aluminium hulls.

The 200 has all standard OptiMax features, such as the dual-stage Orbital Combustion Process (OCP), a massive 60amp belt-driven alternator and SmartCraft instrumentation which displays fuel flow, range-to-empty, engine cooling water temperature and pressure, and alternator charging voltage.

The OCP utilises a combination of stratified and homogenous combustion with low-pressure injection of petrol and air at 5.4bar or 80psi via a 1:1 belt-driven air compressor. In the stratified mode (up to 1800rpm), the atomised air/fuel mix with a fuel droplet size of only five microns is injected near the sparkplug for an air/fuel mix of 14.7:1, although the overall combustion chamber air/fuel ratio may be as lean as 70:1.

Above 1800rpm, homogenous combustion, where the overall combustion chamber air/fuel ratio is 14.7:1, is needed to provide the power and torque required to plane a hull. This results in significantly greater fuel flow, but still only around 15 per cent more than comparable-output four-strokes, which return maximum fuel efficiency in the 2000 to 4000rpm range.

Via an electric pump, lubricating oil is injected directly where needed, resulting in fuel/oil ratios way below that of a comparable oil injected carbie two-stroke outboard. Unfortunately, unlike the OptiMax 90 the 200 has only OEDA 2-Star exhaust emission compliance.

STACER MATCH
Mounted on a 6.92m Stacer 669 All-Rounder Centre Cabin and spinning a 19in prop, the 200 was well matched to the hull, which is rated to 225hp or 300kg on the transom.

It started instantly hot or cold and, despite running on additional break-in oil to the normal fuel/oil ratios, emitted an oil smell only when backing upwind, but never any visible smoke.

Providing the antiventilation plate was kept at least three-quarters immersed, power astern was good and no cooling water starvation occurred. Vibration levels across the entire rev range were very low but the normal Merc V6 howl was present above 3000rpm, making the engine somewhat noisier than comparable four-strokes.

Pushing a total of 1650kg, including two adults, the 200 trolled us at 5.0kmh and 550rpm using 1.2lt/h, and even at 1500rpm where the OCP was still in stratified mode, the averages were 11.5kmh and 4.7lt/h. However, by 2000rpm on homogenous mode, averages were 14.8kmh and 8.0lt/h.

A clean plane was achieved at only 2800rpm averaging 22.4kmh and 14.4lt/h, and when the throttle was floored from trolling revs we planed in only four seconds.

At 3000rpm we averaged 34.3kmh using 16.1lt/h and allowing for a 20 per cent reserve from the optional 330lt tank, the range here is 550km. Even with the wind drag of bimini clears, one metre waves and a westerly wind gusting to 75kmh, we maintained 30kmh at 3000rpm. This speed is ideal for runs to the shelf and back.

Back in calm water at 4000rpm we averaged 49.5kmh and 31.5lt/h and through a full-lock figure of eight turns at these revs only a slight amount of prop ventilation occurred. At my recommended maximum cruising revs of 5000 the averages were 61.2kmh and 59.0lt/h, but at WOT and 5300rpm, where we averaged 65.9kmh, the fuel flow had jumped to 77.5lt/h and noise levels rose considerably.

Powerhead access is good with the spark plugs, fuel injector block, and serpentine alternator and air compressor drive belt easily reached. Recommended servicing intervals are every 100 hours or yearly (including waterpump impeller replacement) after the first 20 hours or three months.

If the engine is maintained by a Mercury Authorised Service Centre the recreational usage warranty is an impressive five years.


SPECIFICATIONS
MERCURY OPTIMAX 200
 
Engine type: Loopcharged two-stroke
Cylinders: 60° V6
Prop HP at rpm: 197.1 at 5375
WOT rpm range: 5000 to 5750
Piston displacement (cc): 3032
Bore x stroke (mm): 92 x 76
Ignition system: Digital CD with electronic timing advance
Charging circuit (amps): 60
Break-in period (hrs): 10
Fuel delivery: Dual stage Orbital DFI
Fuel type: ULP 91 RON
Fuel capacity: Portable tank not supplied
Oil type: TC-W3 Quicksilver Premium
Oil capacity: In-boat 11.4lt
Fuel/oil ratios: 44:1/400:1
Gear ratio: 1.75:1
Transom heights (ins): 20/25
Weights (kg): 225/229
Rec. retails: $21070/$21510
Spare Vengeance prop: $977
 
Servicing costs*
Year One: $636
Year two etc: $362
 
*As per manufacturer's recommended schedule excluding parts. Prices current as of August 08. Demo 200, prop and servicing prices from Lifestyle Marine, Toronto, NSW, phone (02) 4959 1444.

 

 

 

Published : Thursday, 8 January 2009

Prices and specifications supplied are for the market in Australia only and were correct at time of first publication. boatsales.com.au makes no warranty as to the accuracy of specifications or prices. Please check with manufacturer or local dealer for current pricing and specifications.

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