After digging around I finally found out that it is (because I found a jug of it on the boat, hah! After 3 years I'm still finding new stuff stashed away I had no idea came with the boat). It's a product made by "interlube", not interlux as the maintenance log mistakenly referred to. I wasn't able to find it in any online stores, but it is here:
Interlube Corporation.
It works quite well and seems to hold up for several years once you put it on. It's nasty as all hell though, perfect for staining clothes black.