A modified exhaust adaptor plate and centre section reduce engine back-pressure and noise.

O-ring cylinder heads are from the same castings as drag race heads. Enlarged water chambers increase flow close to the combustion chambers and plugs, lowering engine temperature for enhanced durability.

The crankshaft has two additional seal rings, nine in all, derived from racing developments and giving smoother running with better performance overall. Newdesign pistons feature highstrength rings which conform to the cylinder bore, simultaneously enhancing engine sealing while reducing friction.

An electronic, single-point oil injection system is the starting point for a system that pre-mixes the oil before it goes into the engine and delivers precise lubrication throughout the operating range. Oil at idle is reduced automatically, minimizing smoke. There is also an all-new fuel injection system.

All Mercury Pro Max 225X models are equipped with the digital SmartCraft CAN control system. The computer processor optimises fuel, spark timing and knock control for each cylinder independently and drives the system monitor and gauges.

Its Engine Guardian system monitors over 40 engine functions to forewarn of possible problems.

Torque Master and Sport Master gear options feature heavyduty propshafts for durability.