Alpha One
MerCruiser's volume single-propeller sterndrive, rated by Mercury for petrol engines up to 300 hp and diesel engines up to 150 hp in single or twin installations, on boats up to about 65 mph.
The Alpha One name has been on MerCruiser transom drives since the mid-1980s, when it grew out of the R and MR drives introduced in 1983; Mercury's current catalogue spells it simply 'Alpha One', and the drive in production since 1991 is the Generation II gearcase, which is not interchangeable with the 1983-1990 Generation I unit. A separate Gen II row would fork one product into two. It carries a single propeller and a low-drag hydrodynamic profile aimed at fuel economy rather than outright power handling. Design points Mercury emphasises are an integrated water pump, permanently lubricated pivot points and a power trim pump relocated inside the hull. Gen II ratios were 1.50:1, 1.65:1 and 1.84:1 from 1991 to 1995, revised in 1996 to 1.47:1, 1.62:1 and 1.81:1 with stronger gear sets. It is the drive normally paired with MerCruiser's 3.0L four, 4.3L V6 and the current 4.5L V6.
Sources
- 1. Alpha One Outdrives — Mercury Marine
- 2. MerCruiser R / MR / Alpha One (Sterndrive) 1983-1990 parts catalogue — Marine Engine / Mercury Marine parts catalogue
Specifications compiled from manufacturer sources.