Checking the early census records (Year-1800)for a Manuel in SC, there is one that sounds like he could possibly be yours. At the very least warrants some investigation. There is only one in 1790-Manuel Leopard in Edgefield.
There are three in 1800 in the US, but only one in SC. The one that sounds promising is Manuel Bamos. Bamos is a Carribean originated surname and there were Portugese fishermen dispersed throughout the Carribean. He is the only one in his household in 1800, the only one in SC and he is in St Philips Parish, Charleston, SC, a port city. (Shipping)
Unfortunately that is all the information the early records provide. Another note...sometimes records were written as they were heard...his name could have been recorded as Vamos as well.
I wish you luck and hope this leads to something positive. Deb in SC