Honda BF75

I've long believed that Honda's carburetted outboards perform better in their de-rated versions.

For example, the BF25 is better than the BF30; the BF40 scores over its BF50 counterpart; and the BF75 seems a gutsier package than the BF90.

The BF75 is based on the 1.6lt Honda Civic engine, though for ease of servicing and lighter weight, the twin overhead cams and four-valve head have been swapped for a single overhead cam and three-valve head. There are four carbies, and the usual Honda big-engine features of overheat and low oil level/pressure alerts and automatic rev reduction are fitted. A rev limiter is standard, and a speedo pick-up is incorporated in the lower unit.

I first tested the BF75 a few years ago in a twin-rig set-up on a 5.5m Maxicat. The engines planed this hefty hull effortlessly at 2800rpm and cruised unobtrusively in the 3000-3500 rev range.

And on a Stinger 619-E longboat, set up for professional guide work and spinning a 17-inch pitch alloy prop, the single test BF75 seemed perfectly matched to this hull. It proved particularly torquey in the 3000-4000 rev range, though at Wide Open Throttle (WOT) it was no slouch!

Pushing an estimated total of 800kg (including two adults and fishing tackle), according to my GPS, the BF75 achieved a clean plane at only 22.1kmh on 3000rpm. Admittedly, a wedge had been fitted to the transom, to allow the engine to trim further in than normal. But considering the boat's centre-console and fueltank were positioned aft of amidships, the BF75 still had no trouble getting us out of the hole.

This reinforces my belief that with correct use of power trim, and setting up the hull correctly for fore and aft balance, there's never any need for a foil mounted on the antiventilation plate. In any case, the BF75 has a broad second spray plate above the AVP that really increases lift out of the hole.

Opening the throttle to 4000rpm returned 39.4kmh with the engine consuming a mere 7.5lt/hr. In comparison, a carburetted two-stroke 75 would consume 13-14lt/hr at these revs.

The BF75 came alive above 4000rpm, though fuel conventional consumption also increased dramatically. At WOT the GPS showed 58.8kmh at 5800rpm and the engine consumed 23lt/hr still 25% under what a comparable two-stroke would use.

Surprisingly for a hull having a broad planing plank with a full-length keel either side of it, and using an alloy prop with relatively little blade cupping, there was absolutely no prop ventilation in tight figures of eight. The throttle could be left at 4000rpm, and the boat thrown around as though it was a lightweight car-top tinnie.

The test engine started instantly hot or cold, though it seemed slightly out of tune compared to the other BF75s I've tested and rattled a bit at fast idle.

There was also a fuel starvation problem at low speeds, but this was a fault of the fueltank line positioning rather than the engine itself. But apart from these quirks the engine performed beautifully across the rest of its rev range.

The power astern was good, even with the AVP partially exposed, and at all speeds the pilot water discharge was clearly visible.

Servicing the BF75 is straightforward with easy access to the spin-on oil filter, carbies and ignition system. Recommended intervals are every 100 operating hours or six months after the first 20 hours, when the valve clearance must be checked. Regardless of how few hours are clocked up, I would change the engine oil and filter every six months.

There's no doubt that the Yamaha 80, Mariner/Mercury 75 and the EFI Evinrude 70 (which provides comparable performance) will provide stiff competition to the BF75. But as an understressed work engine that's much easier to maintain than the competition. Honda's BF75 fills a niche that should maintain a following for many years to come.