MerCruiser 3.0L

I first tested this petrol sterndrive 18 years ago in a 5.5m Easy Rider half cabin against an OMC V4 Seadrive on the same hull, and was impressed with its bottom-end torque, low vibration levels and overall fuel efficiency.

But since then, with the increasing number of four-stroke outboard competition available in its power range (such as the Honda BF130 and Suzuki DF140), the 3.0L has been somewhat forgotten by the boating media here. And that's a shame, because it remains Mercury Marine's biggest-selling sterndrive - and on the right hull, it outperforms comparable-output four-stroke outboards.

Featuring minimal changes (electronic ignition, revised manifold design) since its debut, the 3.0L still has commonsense engineering. With the same cylinder bore as the MerCruiser 4.3 and 5.7lt sterndrives but with a longer stroke, its cast-iron cylinder block and head have a reputation for survival in saltwater, and the counterflow (non-crossflow) design with pushrod valve actuation and hydraulic lifters is easy to maintain and repair.

The alternator is mounted reasonably high on the block away from any bilgewater, and the two-barrel carbie with automatic choke rarely needs adjusting. On trailerboats where the drive is not left submerged for extended periods, there have been no real reliability issues with the Alpha One drive unit. Other appealing factors include being able to easily work on the engine while the boat is afloat, and that stainless-steel props are not needed to provide outstanding performance.

Although the 3.0L develops 135hp, it does so at only 4600rpm compared to 130hp at 5500rpm for the 2254cc Honda BF130 outboard and 138hp at 5900rpm for the 2044cc DF140, translating to substantially more torque for its output. This was evident in the demo engine which, under similar test conditions to a DF140 (see Trailer Boat Oct 2002), averaged almost the same cruising speed, but at 3000rpm compared to 4000 revs for the Suzuki, while at Wide Open Throttle it was five per cent faster at 4950rpm compared to 6200rpm for the outboard.

Tested in a Sea Ray 176 SRX bowrider and spinning a 21in pitch Quicksilver alloy prop, the demo 3.0L started instantly hot or cold, warmed quickly and didn't blow any oil smoke. Power astern was good and the ignition interrupter virtually eliminated any "clunk" into ahead or astern gear, despite the Alpha One drive's dog clutch.

Pushing 1250kg including two adults, the Dead Slow Troll average was 5.5kmh on 900 revs consuming 1.5lt/h, with low engine vibration levels for such a large displacement four-cylinder, and a clean plane was achieved at only 24kmh on 2500rpm. But when the throttle was "floored" from 1000rpm, the MerCruiser planed us in less than three seconds and would have no trouble deepwater-starting a skier on a single ski.

Cruising effortlessly at 3000rpm using 22lt/h, the average speed was 38.7kmh. The power steering was light but direct and gave excellent directional control at all speeds. Flooring the throttle from 3500rpm produced similar acceleration to a comparable DFI two-stroke.

Other figures included 55.7kmh/4000rpm and 32lt/h, and 65.6kmh at 4500rpm. The WOT average was 70.3kmh on 4950rpm using 45lt/h and normal conversation was possible at the helm. Power trim worked rapidly, and the drive could be trimmed out about three-quarters of the way before prop blow-out.

Maintaining the 3.0L is straightforward with its engine-oil dipstick, oil filter, alternator and power-steering drive belts easily accessible. Recommended servicing intervals are every 50 hours or six months after the first 20 hours, and the waterpump impeller should be replaced every 100 hours or once a year.

The warranty provides two years of general coverage, three years against corrosion perforation and four years for selected ignition components. Mercury says the exhaust emission levels comply with CARB 2008 requirements.