Mercury’s press event inDuck Key, Florida, proved extraexciting after being given theopportunity to run three 300 XSOptiMax outboards bolted to thetransom of Donzi Marine’s 38 ZFO cen-ter console. Utilizing this new outboardon such a platform represents a matchmade in heaven.

The 300XS is based on a 3.2 liter, V-6powerhead. The exhaust port, com-bustion chamber and fuel inductiondesigns are direct descendants fromMercury Racing’s Formula 1 tunnelboat race engine. The crankshaft is pre-cision balanced and a dampenersmoothes out any vibration. New pis-tons and rings feature a composite coat-ing to reduce wear. Anew PCM 07microprocessor optimizes the fuel andspark timing independently foreach cylinder foroptimum, knock free performance. ThisPCM 07 computer also controls themulti-point lubrication system. All ofthis information is simultaneously fedto the Mercury Racing SystemView –Race Edition gauges, which also displayspeed, rpm, engine trim, fuel consump-tion and range.

OptiMax outboards use an exclusivetwo-stage direct fuel injection system.The fuel air mixture is injected into thecombustion chamber at 95 psi. The sec-ondary effect of the air shooting throughthe fuel is to break it into a fine mist,enabling a more consistent, completefuel burn. It’s worth noting the 300XScan deliver fuel savings of up to 45 per-cent compared to older two-stroke out-boards. It’s even designed to providebetter fuel economy than many oftoday’s large, four-stroke engines. The300XS full throttle rpm range is from5,400 to 5,800 on the long shaft modelwetested. Shorter shaft models arerated up to 6,200 rpm.

The 300XS exhaust system is alsonew. It’s water jacketed and routedunder water – exiting the mid-section,just above the gearcase cavitation plate. The ability to mount three of these largeengines on the Donzi 38 is simplified byexhaust adapter plates that accept steer-ing wing plates. Additionally, the off-shore models come standard with aheavy-duty swivel/clamp bracketassembly and trim ram. To expand thenumber of applications for the new 300XS, Mercury Racing offers a large num-ber of gear cases and gear ratios, includ-ing counter rotation.

In order to appropriately test the300XS, Mercury turned to DonziMarine.

Running on a Donzi 38 ZFO, Mercury’s proven 300XS is based on a 3.2 liter, V-6 powerhead and pushed this performer to excellent results.

What’s interesting on the 300XS is the exhaust port, combustion chamber and fuel induction designs are direct descendants from Mercury Racing’s Formula 1 tunnel boat race engine. The crankshaft is precision balanced and a dampener smoothes out any vibration. New pistons and rings feature a composite coating to reduce wear. A new PCM 07 microprocessor optimizes the fuel and spark timing independently for each cylinder for optimum, knock free performance. This PCM 07 computer also controls the multi-point lubrication system. All of this information is simultaneously fed to the Mercury Racing SystemView – Race Edition gauges, which also display speed, rpm, engine trim, fuel consumption and range.

OptiMax outboards use an exclusive two-stage direct fuel injection system. The fuel air mixture is injected into the combustion chamber at 95 psi. The secondary effect of the air shooting through the fuel is to break it into a fine mist, enabling a more consistent, complete fuel burn. It’s worth noting the 300XS can deliver fuel savings of up to 45 percent compared to older two-stroke outboards. It’s even designed to provide better fuel economy than many of today’s large, four-stroke engines. The 300XS full throttle rpm range is from 5,400 to 5,800 on the long shaft model we tested. Shorter shaft models are rated up to 6,200 rpm.

The 300XS exhaust system is also new. It’s water jacketed and routed under water – exiting the mid-section, just above the gearcase cavitation plate. The ability to mount three of these large engines on the Donzi 38 is simplified by exhaust adapter plates that accept steering wing plates.


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