Understand: why is your boss indecisive?
There must be a solid reason behind that lack of firmness. Maybe they’re a first-time boss, promoted thanks to amazing technical skills but with a long way to go before they become proper leaders. It could also be that upper management is hindering them in the first place.
Or perhaps, your boss wants you to seize an opportunity and is actually waiting for your proactive input.
Communicate: make the situation clear
As usual in the workplace, make it about the business - not about you. It’s not you who’s stressed, it’s the project that needs a clear direction. Communication means, of course, pointing out the problem, but also addressing potential solutions. This will save your boss from decision-making overload.
Act: be that key figure in the project
Does your boss need more information? Provide it. Do they miss a clear situation summary from the attached development team? Investigate and report. Would constant updates come in handy? Act as an assistant and, while you’re at it, suggest directions.
Whatever helps your boss making clearer decisions with half the hustle will make you both (and the whole team) look more efficient - successfully landing the project on the side.
Network: look for allies
Don’t do this alone, if you can. Your team can surely help, and so can other people within the company - either mentoring you or providing that extra information you’ll need.
Worst case scenario, your efforts will gain some witnesses.
We’ve seen how “Bottom-Up Management” can disentangle tricky situations, but there's more than that. Being able to "manage your manager" means you may be ready to assume a more prominent role in the office. Ever thought about a promotion?