How many torpedoes did these submarines carry? Where were they stored?

The Gato/Balao/Tench boats usually carried 24 torpedoes. There were times when 24 torpedoes might not have been available. Manufacturing sometimes could not keep up with usage. That was solved after the Mark 18 electrics became available. The Mark 18s were easier to manufacture and there were a few more facilities were building them. However, it appears that the boats never went on patrol with fewer than 16 torpedoes.

The earliest fleet boats, those built in the 1930s, may have only carried 16. The later fleet boats generally were listed as carrying 24, although four of those may have been in external containers.

Visitors to museum submarines are often confused by the answer of 24. They don’t see where that many torpedoes can be stored. That is because 10 were stored in the torpedo tubes. In the forward torpedo room, there were six in the tubes and 10 reloads. Two of those reloads were below the deck plates. In the after room, there were four in the tubes and four reloads.