It wasn't that well known. There was some commerce in Guinea in the 1360's but stopped rapidly.Africa might be an interesting parallel here. It was well known and there were buckets of gold, but the Europeans didn't go in with any urgency. The Portuguese didn't even bother to settle the Cape. America will be to the Europeans much like Africa was.
It wasn't til 1440 that the Cap Bojador off Morocco was crossed again. Even then, there was no rush.
Big money was in the Levant trade