Just 111 days to go till the Dublin Marathon!
It sounds like a lot, but unless you're a fairly accomplished runner, you are behind.
You've only got 16 weeks to train. Are planning on running the full marathon or a half marathon? Big difference...if you're just doing the half I wouldn't worry so much...just run 3 or 4 times a week and make sure you get your mileage up to 18k or so 2 to 3 weeks before race day.
If you're thinking full marathon the same principle applies. You want to get your mileage up to 32km 3 weeks before race day. It takes time to do that safely.
I'm training for the Toronto marathon - Oct. 16th - my run on Sunday was 15km. Next Sunday will be 16.5, back down to 11 the Sunday after that, then up to 19 a week later.
It's a great motivator to stay sober. I'm really glad to have some company on the running front in this forum. Good luck with the training and feel free to send me a note if you have any questions about the training!