VC Theis suh, Have you been going to port lately?
IMCO a single board has to warp.

The original 3 piece was to minimise warp and make it easy to assemble. I wonder what they were glued with or even if they were?

For a remake:
I would cut all the blade pieces from the same timber (whatever doesn't mind too much living under water, why not cypress) into 3" wide strips and face reverse every other one. It would be easy to layout the bolt or rod holes and drill them that way to book them together.

I would use resorcinal glue in a controled environment on a dead flat layup table and clamp the pieces with pipe clamps to the shaft. Then very carefully shape to keep the rods in the center at the outer edge watching for the nuts with ground-down elongated washers. Then glue on a trailing edge piece with no fastenings for final shaping.

Mahogany likes glue. Teak and resorcinol, never tried it - but careful epoxy, not much pressure, would stick it, bet cypress glues well, but moves a lot on outdoor furniture seasonally (in and out of the water) Best choice IMCO is good ole west indian mahogany.