Well, I see no reason to not revive a good thread:
On the Question of Inka Naval Capacities: Though obviously not as good as contemporary Islamic, European or Chinese in naval capabilities, the Inka were better off than many might think:
Sailing reed rafts up to 30 metres long are documented from Moche times and were also used by the Inka for river, lake and ocean travel and trade. The main problems with Andean vessels was that they were rather slow and, being made of reeds, they would decay;
sewn plank boats were known in Araucania further down the coast, so if they could potentially get to the Andes a few centuries (or more) before the rise of Tawantinsuyu, this issue could be resolved. And, once again, as I said long ago on this thread, I think the Inka would adopt Eurasian technology, including more advanced shipbuilding, enabling them to at least build a green water navy to expel hostile Europeans and maybe a small blue water navy to help them dominate Eastern Polynesia, though the latter is a pretty big stretch.