Indexing flywheel

[Liberator*21]

Damn good read guy's !

[RoyE]

On that same note, for the ones with calculators figurin how many thousandths another degree number would be, it’s not evenly proportionate, but variable . The amount of piston travel per degree of crank angle changes depending on rod journal angle. For instance when at TDC and BDC rod journal angle and rod angle are parallel, piston travel is at minimum st this point. As the journal angle to rod piston increases to perpendicular (90degrees) piston travel increases per degree being the most at 90 degrees. So if working on an engine other than a Merc 2.0,2.4, and 2.5 or degrees other than 25BTDC on one of these, unless you better at figurin than me, you will need to set the motor at desired amount degrees and measure the piston travel down to get your spec to set marks on flywheel.

Stumbled upon this thread as I'm going to index the flywheel of an Evinrude V8 this weekend, this was very helpful, thank you Forbes.

As you stated, set motor at desired amount of degrees and measure the piston travel down is one way to get a spec other than the 25 degrees/0.150" for Merc V6.

Other way is calculating the down travel, which can be done using the stroke and rod length.
You can do it manually or use a calculator like this one: http://www.torqsoft.net/piston-position.html
This one is in mm but I'm sure there are other ones.

e.g. for Merc, 2.65" stroke (67.3 mm) and 5.5" rod length (139.7 mm) results in 0.153" piston down travel.