I was a mechE at Caterpillar for 4 years before I decided that my position was a local max in the organization. So I studied, took the GMAT, and applied to b-school. Ended up at NYU and did lots of internships in branding / publishing / marketing and eventually found a route into tech marketing via account management at an ad-tech company that needed someone with solid excel skills & was willing to get on the phone.
Good marketers are eager to talk to people and figure out what their product can/should be doing for others. Then they feed that back to Product. I think Product/Marketing are two sides of the same product development coin.
One way to position yourself as a marketing candidate is as an excellent SME on tech -- you get tech better than your colleagues, so you become invaluable to the team.
I'm actually an engineer who likes to create products but who really sucks at marketing. I never looked at marketeers over the shoulder but now that I am trying to market my own products I realize what a hard and important work is.
I think I did a good job up to the point of finding a real need that people are willing to pay for a solution, but one thing is to get the early traction and a whole other is to actually be able to live from it... the struggle is real :P