Ummm I think you need to talk to a different marine engine guy. The outdrive coupler flange bolts to the same holes as used to hold the flywheel onto the crankshaft flange. Only difference is the marine engine uses studs in the crank that are installed with Loctite instead of the usual flywheel bolts. The flywheel mounts over the studs and then the coupler goes on next and is secured with washers and locknuts.
I've never seen a flywheel like you describe so it might be a marine only use part. Then again I don't work on boats so maybe that's why I've never seen one.
At least now you know what you're looking for.
