E-TEC M2 Gear Case Propeller Aperture
Posted: Thu Sep 09, 2021 1:41 pm
Several years ago I checked the propeller aperture on the M2 gearcase on my model year 2010 E-TEC 3.3-liter V6 225-HP engine. The method I used was to presume that the propeller in use (a Mercury MIRAGEplus 17-pitch) had the diameter specified by Mercury, 15-1/2-inches. Using a drill of 1/4-inch-diameter, I measured the clearance from each blade tip of the three blades to the bottom of the anti-ventilation plate. I found that a 1/4-inch drill would just fit in the gap between blade tip and engine, with perhaps a few hundredths of an inch of additional space, which varied only slightly from blade to blade.
On this basis I think the propeller aperture is 16-inches. I also note that Evinrude's largest diameter propeller recommended for this engine has a diameter of 15-3/4-inches (the Rebel TBX™ 3-blade 15-3/4 diameter 15-pitch).
References:
Evinrude Propeller Selection Guide
https://www.operatorsguides.brp.com/Ope ... 5%20EN.pdf
ASIDE: The asymmetry in blade clearance could be due to perhaps three causes:
On this basis I think the propeller aperture is 16-inches. I also note that Evinrude's largest diameter propeller recommended for this engine has a diameter of 15-3/4-inches (the Rebel TBX™ 3-blade 15-3/4 diameter 15-pitch).
References:
Evinrude Propeller Selection Guide
https://www.operatorsguides.brp.com/Ope ... 5%20EN.pdf
ASIDE: The asymmetry in blade clearance could be due to perhaps three causes:
- the propeller blades could be very slightly non-uniform, which would be quite reasonable for a production propeller, as this propeller was not a lab-finished propeller sample;
- a very small misalignment of the propeller shaft and the anti-ventilation plate so they were not precisely parallel (but unlikely as I will explain below); or,
- the propeller hub kit introduced some asymmetry in the mounting of the propeller on the propeller shaft.