Yamaha CV50

In the March 2002 issue of Trailer Boat we reviewed Yamaha's CV85, a premix and de-rated version of the oil-injected 90A.

As mentioned in that article, Yamaha's 50:1 premix motors have several advantages over their oil-injected counterparts.

One is that during extended periods of disuse, the additional residual oil left on bearings and cylinder walls provides four times the protection of Yamaha's oil-injected motors, which idle at 200:1.

Another advantage is that oil passes through the carbies, lubricating the throttle and choke butterfly shafts and preventing the buildup of verdigris.

There's also no potential for oil gelling should different types of oil be mixed together, particularly in systems such as Yamaha's multipoint oil-injection.

And finally, being a premix motor, there's no oil pump to fail or oil delivery lines that require bleeding whenever the oil filter is cleaned. If the bleeding is not done then air bubbles in the lines can damage the oil pump and prevent it from functioning, starving the powerhead of oil.

Of course all premix fuel goes stale after a couple of months but using Yamaha's 'Fuel Conditioner and Stabiliser' mixed at 125:1 will preserve the fuel for up to one year. The only drawback is that the spark plugs tend to stay wet - but, this won't affect these larger Yammies which have strong ignition systems.

Continuing its theme of offering premix versions of its oil-injected motors, recently Yamaha released its CV50 or the 50HET.

Although it operates on the same 50:1 premix as the CV85, it incorporates more of the features of its three-cylinder 50HETO counterpart.

For example, there is a cold-start fuel primer and electronic ignition timing advance in addition to the power trim and tilt, engine overheat buzzer and rev limiter.

However, the lower cowl tilt switch of the 50HETO has been omitted. Unlike the CV40, there's no overhead recoil starter in addition to the electric starting.

Mounted on a Brooker 485 Freedom runabout and spinning a 12-inch pitch alloy prop, the demo CV50 provided excellent performance on this bulky hull.

It started instantly cold without needing the warm-up lever on the remote control box and quickly reached normal operating temperature.

Only below 1000 revs was there any oil smoke from the 50:1 mix of ULP and TC-W3 Yamalube.

The motor was a little rough for a three-cylinder two-stroke, still, it was significantly smoother than the twin-cylinder CV40.

Above 1000 revs, the vibration levels dropped to no greater than the 50HETO.

Providing the anti-ventilation plate was kept immersed, power astern was good and no cooling water starvation occurred.

At all times, the strong pilot water discharge flow was clearly visible. Pushing a total of 710kg, including three adults, the CV50 trolled quietly at 3.9kmh on 750 revs and averaged 6.4 on 1000.

At 2000 revs it averaged 10.5kmh and due to the Brooker's full-width transom pod, (designed to accommodate hefty four-strokes), it planed us cleanly at only 21.3kmh on 3150 revs.

The single-ram power trim system worked quickly and quietly to take full advantage of this trim-sensitive hull. Cruising quietly at 32.3kmh on 4000 revs, the CV50 consumed 8.8lt/hr. Through tight figure of eights, there was some prop ventilation at these revs.

The Wide Open Throttle average across a chop to 20cm was a very reasonable 46.8kmh on 5500 revs using 22.0lt/hr and the motor remained surprisingly quiet for a carburetted two-stroke.

By omitting the undercowl oil tank, Yamaha has made its 50 even easier to maintain and service. Access to the spark plugs, bowl-type fuel filter, the three carbies and their linkages is excellent.

Yamaha recommends servicing the CV50 every 50 hours or six months for the first two years after the initial ten-hour service, then every 100 hours or once a year, when the waterpump impeller should also be replaced.

There's no doubt that for anglers who use their motors frequently and also fish freshwater as well as salt, the oil-injected 50HETO is worth the extra $1000.

For anglers who only fish saltwater and use their motors 50 hours a year or less, the CV50 is definitely better value for money!