Mercury Marine's 250 OptiMax Jet Drive
I tested Mercury Marineís new 250 Optimax M2 Jet Drive, as installed in Polaris new EX2100 sport boat. Before we give the hands-on results, letís first get the necessary bookkeeping out of the way. The engine proper is a 3.0-liter V-6 powerhead borrowed from Mercuryís line-up of proven outboard motors.
You should also know the powerhead builds its abundant horsepower by way of a two-stage, direct injection system. Simply put, DI technology lends the motor screamingly-fast acceleration along with superior fuel economy and minimal emissions. In fact the Opti jet motor exceeds the EPAís 2006 standards and also boasts a California Two-Star rating. That means itís a clean, mean performance machine. On the purely practical side of the ledger sheet, there is no tedious and messy mixing of the oil with the gas required. This high-pressure direct injection was developed in a collaborative effort between Mercury Marine and the Orbital Engine Company out of Perth, Australia.
As for the jet pump, the Opti motorís horsepower transfers to the water via a progressive pitch four-blade impeller. Its large diameter blades force a massive volume of water through the pump, amplifying thrust, and therefore, acceleration. A twin aperture gate optimizes reverse thrust for greater maneuverability when backing, and just as importantly, when backing off a trailer at the launch ramp.
I tested the 250 Optimax M2 Jet Drive installed in the spanking new Polaris EX2100 sport boat. A full report on that boatís capabilities and performance will appear in next monthís issue. But in the meantime, weíll focus on how well the engine did. First off, I really appreciated the instant starting. There was no choke adjustment to content with. I didnít have to mindlessly pump the throttle lever, wondering whether I was feeding the cold engine enough or too little gas. Instead, I just turned the key, the starter whirred, and then the engine caught. Also because of its DI technology, and quite unlike the old conventional two strokes, there was zero smoke. The idle was velvety smooth without the juking and jiving vibrations we used to see with conventional two-stroke jet motors.
The promise of positive backing in reverse gear was fulfilled. Predictably, acceleration came on very strong. For comparison sake, if you drove two duplicates of same jet boat, one with direct injection and the other with conventional two-stroke power, you would readily feel the difference in the seat of the pants. Similar to an outboard motor, the jet drive features an adjustable trim plate that allows fine tuning performance.
At the end of the day I also appreciated the engine flush system that made it easy to purge brackish lake water from the cooling system. It would have even more welcome of a feature had we been running in saltwater. The impeller blade we mentioned earlier is stainless steel for corrosion resistance.