Could be Iroko, not teak.
A LOT of boatbuilders in the early 70s used Iroko instead of teak. Iroko in comparison to teak is lighter weight and erodes much easier if left bare to 'go grey'. If the wood is bare and deeply erroded in the soft grain ... or the soft grain section is easily 'dimpled' by pressing a thumbnail into it, I'd suspect Iroko instead of Teak.
Varnish and oil based finishes seem to work best on Iroko as the new 'modern' finishing systems (Cetol, Bristol, Honey Teak, etc.) dont adhere too well to Iroko.