Designed for serious offshore use, Yamaha's Saltwater Series II EFI 250 was released last year and provides the performance of its carburetted counterpart and better fuel efficiency without the expense or complication class=MainText>But it still won't meet the US EPA's 2006 exhaust emission regulations.

The EFI 250 is a multipoint fuel-injected version of the carburetted 250 and utilises the same 76? V-six loopcharged 3130cc powerhead, which is a 'stroked' version of the 2596cc 76? V-six used in Yamaha's HPDI Z200N. In Australia, it's available in only one form: an extralong model which is also available with counter-rotation.

However, the absence of an ultralong model means the motor cannot be used on the 6.8m Seafarer Voyager - a shame, as the EFI 250 would really suit this hull.

As with most EFI systems, the 250 is controlled by an Electronic Control Module (ECM). This set-up uses an oxygen sensor in the exhaust system to maintain an optimum fuel/air ratio of 14.8:1 at sea level, enabling the EFI 250 to perform equally well on hot, humid days as on cold, dry ones.

The ECM also cuts-out two cylinders below 2000rpm to further reduce exhaust emission levels, enriches the air/fuel ratio for cold starting, and electronically advances the ignition timing as needed.

All these features give the EFI 250 true turnkey starting in all weather conditions, and the motor is more likely to stay in tune than the standard 250, which has six single barrel carbies arranged in a cross-induction layout and fed by electric fuel pumps.

The Precision Blend varies the fuel/oil ratios from 50:1 at Wide Open Throttle (WOT) right down to 200:1 at DST, and injects oil directly into the crankcase.

Oil is pumped up from a 10.5lt in-boat tank to a 0.9lt undercowl unit as needed. Should the oil level in the in-boat tank fall below the minimum level, engine revs will be reduced automatically.

The system also eliminates the need for a large undercowl oil tank. But with its multiple oil feed lines, it's susceptible to oil 'gelling' or blockages should different types of oil be mixed together - unlike the singlepoint system in the Mariner/Mercury EFI 250 where oil is mixed with petrol at the fuel pump.

Mounted on Kevin Nichol's brilliant Cruise Craft 685 Outsider and spinning a 19-inch stainless steel prop, the demo motor had no trouble handling our 2000kg total (which included four adults).

A clean plane was achieved at only 27.5km/h on 2700rpm and the 250 cruised at 58.1km/h on 4000rpm - more quietly than comparable Mariner/Mercury EFI models at these revs. The 250 consumed 55lt/hr, about what a Yamaha 130B uses at WOT, but through tight figures-of-eight at 4000rpm, there was some prop ventilation.

The WOT average was 80.5km/h on 5400rpm using 107lt/hr and with the motor slightly underpropped for carrying an extra adult or additional fuel.

The demo motor started instantly, hot or cold, and trolled quietly at 700rpm, with hardly any vibration through the Outsider. But up to 1000rpm it emitted as much oil smoke as comparable Mariner/Mercury EFI models.

Above these revs there was no oil smoke.

Providing the antiventilation plate was kept at least three-quarters immersed, power astern was good and no cooling-water starvation occurred - useful for backing this hefty boat off a beach.

Undercowl access is good: the six throttle bodies, ECM, spark plugs and injectors are easily reached.

Yamaha recommends servicing the EFI 250 every 50 hours or six months for the first two years after the initial 10 hour service, then every 100 hours or once a year, which also applies to waterpump impeller replacement.

A 50:1 premix must be used in addition to the Precision Blend during the 10-hour break-in period.

Yamaha's EF250 is well-designed, soundly engineered and should survive well in harsh offshore conditions.