Yeah, varies between 4 and 5 depending on how anxious i get. But i was a bit off, i get 5 at 20kts, and 4.3 at 25. Generally im running at 25 though. Went out of sebastian wednesday, behind bethel shoal to 200 feet, trolled for 4 hours, then did a bit of drifting over the reefs. Burned about 15 gallons covering around 70mi. Also consider that im running a modified V hull, planes better, but SUCKS in any chop in seas over about 2 feet.
Had a 23' Sea Fox with a 114 gallon tank for about 5 years. If the sea were forcasted at 2-3 feet or less I would go out to 45 miles in the Gulf. I got caught in 5-6 footers one day and it took them pretty well. I only do inshore now but I think if I bought another offshore boat I wouldn't get less than 25'.
25 feet and you are fine all day, get twins and you will be even better. That being said 23ft with a single engine is going to be my next purchase, just wont go out in bigger than 5ft seas. For me It comes down to the ecomonics, being in my 20's I cant have a 50 or 60k 30ft boat that I use twice a month.
If you are serious about offshore I would 22' min but we used to do it in a 16' sport cat and a 18' flats boat just have to pick your weather and the biggest thing to consider is storage space or open space gear and coolers and day bags for the ladies it all adds up rod storage is a big issue to you never want to just lay them down on the deck and gunnel storage sucks to beat your reels up bad
I fish a 22 Triton center console in the gulf. 110 gallon tank is more than enough, but I only go 45 miles. I do not go if the forecast is 2-4. I could but it is not as much fun and you can always fish inshore on those days. I fish up to 6 people, 4 comfortably. It has a deep v and lots of freeboard. The type of boat can be as important as the length. My 22 Pathfinder bay boat fished a lot of days offshore, but I did have waves come over the bow due to the lower freeboard and that's not fun.