Sub-Saharan Africans on their own never even made it to any of the islands off Africa. Every inhabited island off the coast of sub-Saharan Africa was first settled by non-Africans. That would put the Neanderthals of 100k+ years earlier ahead in the seafaring technology department.
Keep in mind that Europeans and Asians have Neanderthal genes, and sub Saharan Africans don’t.
You are aware that whatever may be found to suggest ancient seagoing only survives on what were once the highlands of a once much larger world in terms of land areas once available?
So, on two levels there is a problem with your confidence: first all the best evidence that may exist (or may have existed) is likely under even hundreds of feet of water; second since we ARE talking highlands of that lost world here, even though today they may be lowlands, there was ample time for cultures to arise that were suited to being just where they are.
Just as the cultures of the Eastern Europe and Asian steppes lack a history of using boats — like the Slavs before the Rus came they may have a landbound attitude because that’s just their conventional thinking, and even the Rus, Varangian/Viking derived as they were, absorbed that attitude until Peter pulled them out of it — so one cannot say they lacked ability just because they didn’t do A or B.
I would also point out to you that Sub Saharan Africa, under the effects of Islam, suffered a general devastation of many cultures and Mali notably got rich and fat shipping out other Africans across the desert to Arab lands. Some folks say, and not incorrectly, that Islam with the destruction and loss of North Africa as well as endless piracy and many slave raids caused the dark ages but compared to what happened to the classical worlds the tribal lands or small kingdoms that once were scattered around Africa really got hammered ... and the wilderness took everything once people were gone.