Honda BF150 outboard motor review

Originally published in TrailerBoat #254, March / April 2010

This engine can develop 197hp at 7000rpm in a Honda Accord Euro car, so the marine version that is the Honda BF150 outboard motor is very under-stressed for its output.

HONDA BF150

Released on the Aussie market in late 2003, the Honda BF150 outboard motor has VTEC or variable intake valve timing which holds the intake valves open longer to increase airflow into the combustion chambers and substantially increases top-end performance over its de-rated BF135 counterpart. The VTEC system combines with Honda’s Variable Air Intake System also used in the BF135, which lengthens the air intake flow at low speeds to increase bottom-end torque, but shortens the flow above 4000rpm to improve engine ‘breathing’ and increase power.

Midrange fuel efficiency is very good due to the lean burn air/fuel ratios, up to 18:1 between 2000 and 4000rpm, while the cooling system has three circuits to maintain consistent engine temperatures. The cylinder head thermostat opens at 50°C with the cylinder block thermostat opening at 60°C and the exhaust manifold cooled directly by unheated water.

Like the Honda BF135, the Honda BF150 outboard motor has chain-driven camshafts with the chain running in an oil bath and the flywheel at the top of the powerhead instead of at the bottom as with the BF115 which has a belt-driven camshaft, even though it’s a 16-valve engine.

The camshaft chain on the Honda BF150 outboard motor also drives twin counter-rotating balance shafts, as the old rule of thumb with four-cylinder petrol engines — which essentially are two twin-cylinder engines joined together — is that above 2.2lt of displacement the out-of-balance forces are too great for just crankshaft counter balance weights to handle effectively.

Having chain drive is a real benefit for reliability as the engine is an interference type where, should a camshaft belt break, the valves could contact the piston crowns and result in expensive repairs.

The only belt drive for the BF150 is the alternator, which produces 30amp at 1000rpm and 40amp from 2000rpm to Wide Open Throttle. However, about five amps are used to run the engine management system and EFI, which increases the ignition timing advance for more power and torque when higher-octane petrol is used.

PERFORMANCE ON THE WATER

Mounted on a 6.5m Makocraft Island Cab 650 and spinning a 16in Solas Titan stainless steel prop, the Honda BF150 outboard motor was perfectly matched to this hull which is rated to 225hp.

Pushing 1.8 tonnes including an optional hardtop, two adults and a full 300-litre fuel tank, the Honda trolled us at 3.9kmh and 710rpm using 1.9lt/h with scarcely any vibration through the hull structure.

Increasing the rpm to 2000 returned 16.7kmh and 7.1lt/h, while a clean plane was at 25kmh and 3450rpm. At 3600rpm, the average was 26kmh for a clean plane offshore in a swell.

Increasing the rpm to 4000 returned averages of 36.2kmh and 23.6lt/h and through full-lock figure of eight turns at these rpm no prop ventilation occurred. At 4500rpm when the VTEC cut in, the 650 accelerated rapidly out to WOT and at my recommended maximum cruising rpm of 5000 the average was 51kmh. The WOT averages were 65.9kmh and 59.3lt/h at 6000rpm where the Honda was noticeably quieter than any comparable-output DFI two-stroke outboard.

The demo engine started instantly hot or cold and didn’t blow any oil smoke, nor was there an oil smell backing upwind. Providing the antiventilation plate was kept at least three-quarters immersed, power astern was good and the Honda remote control box had a positive shift ‘feel’ into ahead or astern gear.

EMISSIONS

With its combined hydrocarbon, oxides of nitrogen and carbon monoxide emissions of 95.0gm/kW/h the BF150 is the cleanest-running outboard in its power range, two or four-stroke, and like all Hondas has an OEDA 3-star exhaust emissions rating and a five-year recreational-usage warranty.

HONDA BF150 SPECIFICATIONS

* As per manufacturer’s recommended schedule excluding parts. All prices current as of January 2009. Demo BF150 from Honda MPE, Campbellfield, Vic, phone (03) 9270 1111; prop and servicing prices from Coastal Outboards, Charmhaven, NSW, phone (02) 4392 8866.

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Originally published in TrailerBoat #254, March / April 2010