TC-W3 is designed for the somewhat cooler operating temps of outboards and has zero ash additives usually. Ash would be metallic detergents/antiwear compounds that could leave behind some cc deposits in these engines. So other, non-ash detergents/anti-wear additive/base oil combinations are used in TC-W3.
JASO-FC and ISO-L-EGD will typically be low-ash, but designed for higher operating temps of air-cooled engines, or in the case of PWC's, API-TC is usually the one to look for.
Will you grenade your engine using TC-W3 in you weed wacker? Doubtful and way better than using SAE 30 for mixing or something worse. But it is not ideal for this use, see? Same with using ISO-L-EGD or JASO-FC in your outboard. It would work for a long time, but not ideal, see?