Originally Posted by TFBubendorfer
MacMillan gives 3:22 for a 1:36 half and 3:19 for a 71m 10 miler. That should give you an indication, but it's certainly not set in stone. My own marathon times are usually 5 minutes slower than MacMillan suggests, others manage to hit their times much better or even exceed them.
3:15 might be a bit optimistic, but it's up to yourself. Some people do indeed manage to surprise themselves.
+1 to what Thomas says...I've recently done a 1:35:30 HM but I'll be happy to break the 3:30 in Cork next week. Also, if it's your first one you should leave an extra few mins grace from your absolute target.
I'd suggest go with the 3:30 pacers and if you're feeling really good after 15 miles or so then maybe push on a little and if still good at 20 miles push on even more. This would leave you a time of about 3:20-3:25 depending on how much you push yourself.
If you go out with 3:15 and it's just a little too fast for you by half way you will probably really struggle to get 3:30 by the end.