"I've never done it before, but it's quite a challenge. I've been out on the course quite a bit trying to work out the pace," she said.
"You have to have a plan before you start and you've got to try and do it so that if anyone is with you, you don't kill them. You want to get them round at the right time."
She said the trick was to run at a constant pace - not always easy on the undulating Rotorua course.
"All the pacers are volunteers and it's quite an undertaking really because you want to get it right for people, especially if it's their first marathon. You want to keep it constant, so you don't wreck anyone's race, so that's the real trick with the hills of course.
"I've been out there mapping it out. I think I've got the pace sorted - I've got it written all over my arms."
Crowley said it was a new experience to tackle a marathon having put in so much preparation.
"Normally I just go, and see if I can keep going."
Crowley completed the Tarawera Ultramarathon in February and said then that she had never quite managed to compete the Rotorua marathon in a time she was happy with. However, she decided this was not the year to try and do that.
"Because I wasn't going to compete in it, I thought 'I need to go and help because it's the big Rotorua event. I couldn't really see myself standing on a corner clapping somewhere, or marshalling, and then I was looking, because the Auckland club organise the pacers because they are a bigger club, and they were missing the 3h 45m [pacer] and I thought, I could do that'."
The half marathon starts at 8am today with the marathon runners setting off at 8.20am.