Mercury Optimax 115 135 150 175 2000-2010 Service Manual

OptiMax was Mercury's direct-injection two-stroke brand, in production from 1996 to 2018. It was designed as a new powerhead, not a fuel system bolted onto an old engine, and developed with Orbital Engine Corporation of Western Australia. Instead of injecting straight fuel, a belt-driven compressor delivers pressurized air and fuel to a nozzle at the top of each cylinder. Each nozzle sprays a fine air-and-fuel mist directly into the cylinder after the exhaust port closes. The system runs in stratified and homogeneous modes, so the engine gets a normal 14.7:1 air/fuel ratio and the oil/fuel ratio varies from 44:1 at full throttle to 400:1 when trolling. Mercury claimed up to 50 percent less oil and about 45 percent less fuel than a conventional two-stroke, and the engines run virtually smoke-free. From 2001 they wear a distinctive wave-like top cowling.

The 135, 150 and 175 share a 2.5-litre (2,507cc) 60-degree V6 powerhead with a diecast alloy block and head built for saltwater cooling. A 150 in 25-inch extra-long shaft weighs about 201 kg. Testers noted it is noisier than the four-stroke competition, and trolling fuel use is comparable to a 60 hp four-stroke. Mercury recommended servicing at the first 20 hours and then every 100 hours or annually.

The 115 is the odd one out. The original V6 115 has a belt-driven 60-amp alternator. The later 1.5-litre three-cylinder 115 uses the same pistons and other components as the larger V6 200-250 OptiMax range, which keeps parts easy to find.

The OptiMax came as long-shaft (20-inch) and extra-long-shaft (25-inch) outboards, with remote steering and power trim and tilt on the larger models. It was available with counter-rotation for twin installations.

This factory service manual covers the procedures, torque specs, and diagrams needed to keep a 2000-2010 OptiMax 115/135/150/175 running the way it was built to.