Can you supply some details about the business-related dynamics at play here, specifically whether or not you're being paid any flat rate (or just equity), what your share is compared to the marketer, and whether you have a contract that puts you on the hook for anything?

A recent article ( http://www.hailpixel.com/articles/technical-cofounders ) and the accompanying HN discussion ( https://news.ycombinator.com/item?id=8959377 ) highlights how exploitative the "technical co-founder" relationship can be -- you may want to evaluate whether your situation resembles something like that and whether you want to re-negotiate or leave.