Honda BF40

Since its local introduction in 1993 (as a 35hp), Honda's BF40 has proven to be a torquey, reliable and fuel-efficient powerplant for aluminium runabouts to 4.5m.  And every time I have tested one, each motor has started reliably hot or cold, had remarkably low vibration levels for a three-cylinder four-stroke and has handled a wide range of loads with alacrity.

The BF40 comes with a comprehensive list of standard features, including low oil level/pressure and overheat alerts (a loud beeping noise and automatic reduction of revs), a rev limiter and a lower unit speedo pick-up.

Recently I tested one again and all it did was confirm my belief that this is one of the best four-stroke outboards on the Aussie market.  Straight from the box, the test motor performed faultlessly on a Horizon 4400 Runabout featuring the new Series 2000 hull.  After a touch of choke and a slight raising of the fast idle lever, the motor started within a couple of seconds of turning the key and as expected of Honda products, no oil or rich mixture smoke appeared.

Once started, the motor was so quiet you had to check the pilot water discharge to see whether or not it was running!  The slimline single-lever control box had a positive, almost clunk-free shifting action and progressive throttle control.

Thoughtfully, Honda has provided a spare emergency ignition cut-off switch clip in a recess, ahead of the throttle/gear lever.  Spinning the standard 13-inch pitch alloy prop and pushing a total load of 550kg (one-up), the test motor had an almost vibration-free Dead Slow Troll (DST) of 800rpm.  Even with the anti-ventilation plate partially exposed, the test motor pulled well astern and did not suffer cooling water starvation (useful for backing off a sandbar or out from a beach).  And when the anti-ventilation plate was immersed, merely shifting in or out of gear without opening the throttle allowed the hull to be positioned exactly where wanted.

According to my GPS, nudging the throttle to 1000rpm returned 8.8kmh, while 2000rpm averaged 12.2kmh with the hull still in a full displacement mode.  At 2500rpm, the hull started to plane and was full at 26.4kmh and 3500rpm.

An effortless cruise was achieved at 31.6kmh and 4000rpm and at Wide Open Throttle (WOT) and 5600rpm, the BF40 averaged 49.2kmh - an excellent result for a 40 on this size of runabout.  When two adults and two kids (bringing the total to 740kg) were added, the motor maintained a fairly quick 5.4kmh at the DST revs of 800.  And though a clean plane wasn't achieved until 28.  3kmh and 4000rpm, once up, the motor maintained these revs up or downwind, using the power trim to quickly adjust hull angle.

The fuel consumption at these revs was a very reasonable 5.5lt/hr.  At WOT, the BF40 averaged 47.4kmh with the revs holding at 5600 and the fuel consumption at 14.1lt/hr.  Despite a noise-amplifying canopy being fitted, at WOT the noise levels were low enough that a normal conversation could be held at the helm.  However, there was significant propeller ventilation in tight figures-of-eight, more a fault of the hull's keel design than the motor's lower unit.

Servicing the two-valve head BF40 is straightforward and intervals are recommended every 100 operating hours or six months after the first 20 hours, where the valve clearances must be adjusted.  The sump oil should be changed every six months (regardless of how few hours are clocked up) and the waterpump impeller should be checked and/or replaced every 100 hours or once a year.  The spin-on, car-type oil filter is easy to change and access to the three carbies for tuning is very good.

With all the other four-stroke 40s now on the Aussie market, the BF40 will have a tough time competing.  However, judging from its performance over the years, there's no reason why it shouldn't survive the onslaught!