Look on top of your steering arms inside for signs or water, wet rusty crud usually, if your pin seals are leaking. The swivel shaft is steel and rust. Seals don't seal on rusty pitted surfaces.
Is the top of your transom assemblies under water when beached?

US 1 Yes, the top of the transon assemblies are under water when beached, so the swivel shaft is a likely spot for the leak. I'll check them out this weekend.

Thank you.