I think this really depends on the course, 10 hours at IM Florida is not really special, prob equals 10:30 + at most other IMNA events.

Running 3 hours is really not very fast "IF" you can manage to get your running mileage up for a good 6-12 months.

I would guess that

3:00 = 10:40 standard IMNA course

2:45 = 10:00