So I pulled the 540 out of my Cobalt 253 this winter for some routine maintainence and just getting it back together this week. While the motor was out, I decided to clean up some rust on the flywheel and replace the drive coupler since I reused the unit off the original 454Mag. I ordered the "HD" coupler (the one with the snout and steel splines) and the newer part# is 861523A11.

Installed per bulletin with countersunk cap screws and have .015 runout.....measured with dial indicator on the front of the snout. Is this normal and will it cause issues with vibration or alignment?

I put the original LC-5503-1 coupler back on and measured .003 runout just in front of the splines. The LC-5503-1 is a beefy machined aluminum unit with a lip that fits tight into the crank snout. These new HD" units look like cheap stamped metal welded by a junior high student....that flexes when you tighten the bolts. For what Merc charges for these units I expect more.

Any tips or tricks I am missing?