Yamaha F80A

De-rated from its F100A counterpart, the F80A is an understressed motor that suits commercial as well as recreational applications.

Based on the European Ford Sierra car engine, the F80A has a belt-driven DOHC, 16 valves and four single-barrel carburettors. Long and extralong shaft versions are available.

As with its uprated counterpart, the F80A has CD microcomputer ignition, which electronically advances the ignition timing during both normal operation and cold starts, plus an automatic choke system with a PTC (Positive Temperature Control Thermistor) system. Combined with a cold-start fuel primer, this eliminates having to operate electric chokes that can sometimes be a 'hit or miss'. The microcomputer also automatically reduces engine revs to a 'safe' level should the engine overrev, overheat or if the oil pressure and level drops below the required limits. The alternator produces a maximum of 20amps but also 12 at only 1000rpm.

A while back I tested an F80A on a 5.2m Southwind UB520 centre-console. Spinning a 17in pitch stainless steel prop and pushing a total of 800kg, including two adults, the demo motor provided more than enough power for this hull. And with its understressed powerhead, it would have easily handled much heavier loads carried aboard this hull.

It started instantly hot or cold, warmed quickly from cold and never emitted any oil smoke. Providing the antiventilation plate was kept immersed, power astern was good and no cooling water starvation occurred. At all speeds the pilot water discharge was clearly visible. Vibration levels across the entire rev range were lower than one of the competitors and on par with another. The motor was very quiet up to about 4000rpm, where the carbie induction roar started to become noticeable.

The F80A trolled at 3.8kmh on 700rpm using 1.0lt/h, and cruising at 4000rpm it averaged 37.5kmh using 10lt/h. Through tight figures of eight at these revs, there was no prop ventilation. At Wide Open Throttle (WOT), the Yammie averaged 59.5kmh on 5800rpm using 26lt/h. At this speed and these revs we could hold a normal conversation at the helm.

In comparison, mounted on a 5.8m centre-console longboat, spinning a 17in alloy prop and pushing a total of 800kg, a competitor's four-stroke 75 averaged 39.4kmh at 4000rpm using 7.5lt/h. The WOT average was 58.8lt/h on 5800rpm using 23lt/h.

The F80A appears straightforward to service and powerhead components such as the carbies and spin-on oil filter are easily reached. Recommended servicing intervals are 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.

Although the camshaft drivebelt should last about 800 running hours before needing replacement, I would check the belt every 100 hours or once a year for any cracks or deterioration when checking or replacing the waterpump impeller.

In addition to the yearly service, I would change the oil and filter every 50 hours or six months (total parts cost about $50), particularly if a lot of trolling is done during this period. This will help reduce the build up of 'sludge' in the sump that occurs during extended trolling periods when four-strokes run at least 20° cooler than at higher revs and condensation from the water vapour created during the combustion process can bypass the piston rings. The resulting emulsified oil and water mix can block the oil pump strainer screen.

I recommend using Yamaha's own SAE10W30 oil in winter and SAE10W40 oil in summer. As marine four-strokes operate under entirely different load conditions to their automotive counterparts, never use an SAE20W50 car oil in the F80A, and don't use the 10W30 oil in summer.

According to owner reports, Yamaha's F80A is a very reliable motor and stands up well to frequent saltwater usage.

But as with all automotive-based engines, it's better to freshwater flush the motor after each saltwater run.

The warranty provides two years of coverage for recreational usage.