Can I ran a sub 3 marathon?

I think you need to run faster than race pace one day a week. Other than that, It will be more important to run the proper pace on race day. You should start the first 3 mies at about 7:15 pace and then work down to race pace. When you get to 20 miles, you can then pick up the pace to reach your goal.

You're close.

Suggestions:

-Overall mileage is plenty adequate. Go more by feel, and let the mileage come something like 86-68-82-85-63, etc.. Allow your body to absorb the training with lower mileage weeks, with more strides, drills, etc..

-Do marathon pace runs every other week,topping out at ca. 16 miles, and replicate the race scenario wearing racing flats and with taking of gels, fluids, etc..

Alternate the MP runs with a fartlek/interval session @ 5K-10K pace, or shorter race.

-One minor session of speedwork/week, 150-400's at fresh pace to keep the turnover. Some of this on hills.

-Slower on your easy days. Start at 8:00 pace and only increase if you feel really frisky.

-Long run should go up to 22+ miles. Again, start at 8:00 miles, then negative-split if feeling good.

'and recently did a 10K and half-marathon last Spring (in March) with times of 38:55 and 1:26:23 '

That's not recently. Have you not raced since then?

If you stay healthy, I think your chances to break 3:00 are very good to great. First off, you're 19 and you're running 80 MPW, all of them essentially at general aerobic pace -- so assuming you don't break down, you're a couple of 20 milers from having sub-3 in the bag. I agree with everything Last Lap writes below. Your mileage is there, so give yourself more easy days. I'd love to see what you could run on a 20 mile long run if you gave yourself 10 days of easy running (8:00-ish pace), and then hammered the long run. I bet you could comfortably cover 20 miles at 6:45 pace right now if you were more rested...

Last Lap wrote:

You're close.

Suggestions:

-Overall mileage is plenty adequate. Go more by feel, and let the mileage come something like 86-68-82-85-63, etc.. Allow your body to absorb the training with lower mileage weeks, with more strides, drills, etc..

-Do marathon pace runs every other week,topping out at ca. 16 miles, and replicate the race scenario wearing racing flats and with taking of gels, fluids, etc..

Alternate the MP runs with a fartlek/interval session @ 5K-10K pace, or shorter race.

-One minor session of speedwork/week, 150-400's at fresh pace to keep the turnover. Some of this on hills.

-Slower on your easy days. Start at 8:00 pace and only increase if you feel really frisky.

-Long run should go up to 22+ miles. Again, start at 8:00 miles, then negative-split if feeling good.

Race again, it appears that you may have gained fitness since your last races. Those previous times don't indicate that you can, but, again, those are old times.

Thanks for the advice guys. Yeah, I've been told to run my easy days at around 8:00 pace but I'm so use to running 7:30 or below because that's what how fast we ran our miles in high school. I'm definitely going to try to build my long run up to 20+ miles and will alternate each week with a marathon pace tempo and an actual tempo (miles run at around 15K-10K) pace. I should probably add some hills and strides also like you guys said.

Also, yeah I technically haven't raced in a while (I never race in the summer, just like to train) so I think I will do a half marathon probably about 6 weeks before to gauge my fitness and see if sub 3 is plausible. I'm guessing I should be around sub-1:25 or sub-1:24? Also, does anyone know how fast of a course Richmond Marathon or OBX is (I live in Raleigh, NC)?

My 1:23:15 in July ended up being a 2:58:15 in December(rounding). But that includes a 45 second bathroom stop -- so a 2:57:30 without it. And I had a good HM but only a so-so marathon. So I would guess that you are golden with a sub-1:24, and probably good with a sub-1:25.