Hello, I swapped out motor for my daughter's versa.
When the engine cranks it keeps blowing the Positive Battery cable fuse PN# 24380-79915.
Where would enough current come from to melt it?

mac, this is just a guess , and something to verify for your situation , but I believe when there is that Hi amperage fuse right at the positive terminal - it's to supply the FUSEBOX ,usually the one in engine compartment , the STARTER is a DIRECT SECOND HEAVY cable in addition to the fused portion , and makes ONES SOLID HEAVY connection from positive post to starter. So I believe you're STARTING current is going through that fuse which designed only to supply Fuse panel and car systems only .Since you didn't state size of the fuse -remote possibility is vice versa - same problem though where starting current plus ALL OTHER AMPERAGE is going through the fuse (probably not supposed to ? )

If the starter changed the 'new' one may be old enough to pull too much amp to blow fuse. Or a cable routing error while replacing things to make a short somewhere, often the way the actual starter cable attachment was redone can splay the terminals enough to barely touch the wrong something.

What mac said as well.