Yamaha F350 Outboard

The mega outboard

First impressions of this outboard are impressive. Viewed from the rear, it's surprisingly narrow but higher in the cowl than the F250 model. To achieve this, Yamaha designed the exhaust manifolds to lie in the V of the 60-degree block and the extra two cylinders located on top.

The manufacturer is also touting an improved water-resistant cowling and latch system, complemented by an air intake that draws air via a labyrinth of passages that trap water and send it to a pair of drains in the lower cowl. The air inside of the cowl is drawn into the single 81mm diameter intake at the front of the block and this is monitored by an Engine Control Module (ECM) before channelling the air via dedicated 'pulse tuned tracks' that serve each cylinder. In fact, seven different sensors measure atmospheric conditions and engine functionality, to continually and instantly adjust fuel/air mixture for optimum performance and economy.

POWER HEAD
This powerhead features four valves per cylinder and their lift, duration of opening and overlap may be advanced and retarded via the variable camshaft timing to give greater torque between 2000 and 3500rpm.

Yamaha claims this engine has improved exhaust pressure reduction at the propeller hub to allow for easier breathing. Their breakdown diagrams show a water feed onto the propeller damper that reduces wear and tear from the heat. The rest of the exhaust is expelled via a dual labyrinth system below the back of the cowl. To keep such a large and complex powerhead cool, dual inlets suck the water into the leg. In addition to the usual inlets on each side of the leg above the gear case, there are others at the front of the gear case bullet. The bearings in that gear case have also been beefed up considerably.

Yamaha have a special line of propellers for this range of engines called 'Saltwater Series XL'. This engine can spin a 25in prop, about 9kg apiece and feature huge hubs for maximum exhaust emission.

When firing, each cylinder has its own ion sensor which detects the production of ions in the burn and based on the results, the ECM adjusts the timing to achieve improved combustion.

The pistons are lubricant coated for increased anti-wear and anti-seizing qualities, and the cylinders have a spiny outer sleeve which apparently keeps the cylinder more symmetrical than in a standard bore, thereby increasing efficiency and reducing oil consumption. The spines on the outer wall of the cylinder also create an increase in surface area, which makes for improved heat dissipation into the water jacket in which they sit.

There wouldn't be a boat available today that had the V8 in mind when it was designed. The issue with cowl height and forward length can be a problem when tilting motors, so Yamaha have an adjustable maximum tilt angle that is factored in by computer to the Diagnostic System at the time of installation to suit your boat.

VARIABLE TROLLING
As with some of Yamaha's smaller motors, variable trolling rpm can be adjusted between 600 and 1000, by 50rpm increments.

Dry weight of this outboard motor is 365kg without the propeller, so some beefing up in the mounts was undertaken in the form of four forged aluminium types and an oversized mounting bracket. This bracket has the same hole-pattern as the F250 but with the addition of another two bolt holes taking the number of bolts through the transom to six.

Having done away with control cables, the engine is connected via Command Link which electronically controls the throttle plus shift, and is available in single, twin and triple configurations, and single and dual stations. For those going to twin and triple rigs, engine synchronisation is at the finger tips when on the helm.

Now if 350 horses will push you over the limit stated by the manufacturer of your boat and you still need the thrust, Yamaha will be bringing this engine out shortly in 300hp.

CONSUMPTION
While both boats revved their engines out to the max at 5900 rpm, the Stabi-Craft achieved a speed of 79.6kmh, using 119.4lt/h. The Commodore was just ahead of it fuel-wise at 117.5lt/h for 79kmh.

Holeshot on both boats was brilliant, although slightly odd on the Commodore which simply moves forward and slides along the surface on the plane without having to climb out of the hole. This boat had a Seastar hydraulic helm to Yamaha's power-steering pump. Steering was a dream from lock to lock in all situations.

Starting the engine, there is the sound of a rush of air and a lot of exhaust bubbles, and operation is as with any of the other big Yamaha four-strokes; smooth and quiet.

The pair of the V8s fitted to the Grady-White provided plenty of power to push the 5200kg hull with eight adults aboard onto the plane. With both engines synchronised and running at 5900rpm, the Grady-White was clipping along at 42.8kts with a fuel consumption of 250lt/h for both engines.

The noise levels in the cockpit of all boats were very acceptable by today's four-stroke standard.

We were half expecting the throb of a V8 but not so. With the leg tilted up and the exhaust hub near the surface, there was a slight hint of a burble, but nothing like you would get out of your V8 with twin exhausts on the highway.

Those looking for a twin rig will like the digital remote control for these engines which is as smooth as silk.

Depending on the length of the shaft required, you can expect to pay between $38,000 and $43,000 for the pleasure of owning one of these awesome outboard engines.

Fore more information: phone (07) 3906 7000, or visit http://www.yamaha-motor.com.au/