NEW YAMAHAS
Both Assault RIBS featured this month have new generation Yamaha F-series four-stroke outboards.
The larger Assault 610 has the new F90 and the smaller Assault Vesta 380 has a tiller-steer F25.
The Yamaha F90 is a 1.8-litre four-cylinder, 16-valve, inline single overhead camshaft engine based on Yamaha’s F115B. It has a larger capacity block than the old 1.5-litre F80-F100 it replaces, but is more compact and 10kg lighter thanks to the adoption of a single overhead camshaft design (SOHC) actuating four valves per cylinder. This valve train design was first seen in Yamaha’s award-winning F70A introduced a few years ago.
The powerhead, valve train and combustion chamber design, along with lean-burn technology, deliver fuel savings of up to 10 per cent over the previous generation engine, according to Yamaha, and the new F90 is said to be quieter too.
From our experience with the new outboard, Boating can confirm it’s an exceptionally quiet unit, and smooth running as well.
The new Yamaha F90 is available in two shaft lengths and is fully compatible with Yamaha Command Link digital gauges, as well as third party multi-function displays, GPS units and fish finders through the NMEA2000 protocol.
The Yamaha F25 is a new addition to Yamaha’s range of fourstroke outboards. It’s a lightweight unit with electronic fuel injection engineered to exceed the performance of Yamaha’s veteran 25N two-stroke, a reliable, strong-performing outboard model that’s been popular for many years.
In addition, the new F25 improves on the existing F25 fourstroke, with better fuel economy and sharper performance.
An exciting feature of this engine, and new to the Yamaha fourstroke range, is battery-less fuel injection. This technology allows effortless one-handed pull-starts from a seated position while careful calibration of the EFI settings provides strong acceleration and impressive performance.
Yamaha has achieved a weight reduction of 20kg over the outgoing F25 model, through redesigning the engine bracket and refining the drive unit. The F25 now offers the weight and balance benefits of a two-stroke outboard but with the advantages of the latest Yamaha four-stroke technology.
Engines in this size range are typically used on tenders and small RIBS, or small sport fishing craft. For fishers, the F25 has some very useful features, including Yamaha’s variable trolling switch. This lets you vary engine speed in 50rpm increments between 750 and 1,050rpm for optimal lure presentation when slow-trolling. Trout trollers will welcome this feature.
Like larger engines in the Yamaha range, the F25 is compatible with Yamaha Command Link digital gauges. The F25 is available in manual start with tiller handle, electric start forward control, electric start forward control with power trim and tilt, and with the addition of a kit, tiller-steer, electric start. Two shaft lengths are offered.