I can't say about Mohawks, but I've had a Mad River Explorer, a MR Eclipse, and a Dagger (now MR) Legend.  The Royalex in both the Explorer and Legend was a full 3/8" thick, while the Eclipse's (Royalite R-84) was slightly thinner.

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im guessing you are talking one like that?

specs from their website

SOLO 13

Length: 13′, Beam at gunwale: 29″, Beam at 4″ waterline: 30.25″
Depth: at bow 18″, at center, 12.5″ at stern 18″
Approx. weight: 41 lbs. (Royalex), 36lbs (Royalite R-84). Estimated capacity: 300 lbs.

SOLO 14

Length: 14′, Beam at gunwale: 29″, Beam at 4″ waterline: 30.25″
Depth: at bow 18″, at center 12.5″ , at stern 18″
Approx. weight: 44 lbs. (Royalex), 39lbs (Royalite, R-84). Estimated capacity: 375 lbs.

so as for determining which material, i guess weigh them? i assume it would also say which material on the riveted in plate with the serial number and such

Anyone here ever own a Mohawk canoe? Or does anyone know how to tell if a Mohawk is either Royalex or Royalite?

I saw a little Mohawk solo pop up locally. Wouldn't be for Q use, just knocking around close to home.