Mercruiser Black Max Aluminium 21 inch Pitch (21P) propeller.
The Mercury Mercruiser Black Max 21P is the propeller type used on Alpha one Gen 2 Sterndrives. Each genuine Mercruiser prop comes with a new Flo-Torq hub kit.
If your replacing your existing Alpha One prop and are not sure what size you have, look between the blades and you will see stamped into the casting, a figure such as 21P or the part number. This means you have a 21-inch pitch Mercruiser propeller.
To correctly size your prop, the boat should be tested with a clean bottom, a full tank of fuel and one person on board. If you can reach maximum revs as per the engine spec, then you have the correct prop fitted. If the engine over revs, go up 1 or 2 sizes, i.e. from a 19P to 21P. If you cannot reach maximum revs, then you will need to drop down 1or 2 sizes, i.e. from 21P to 19P.
Each Mercury Black Max propeller is supplied with a Flo Torq II Kit, Part number 835257Q1 suitable for an Alpha One Gen 2 Sterndrive.
If your Mercruiser propeller is damaged, consider changing it as vibration will damage the Sterndrive and it can cause water to enter the gearbox.
Size; Size; 14 1/4 x 21 R/H Alumunium 3 blade prop
Fits: Mercruiser Alpha One Gen 2 Sterndrives
Mercruiser Part No: 48-832832A45