Grandbanks Tom. As others have said, it all depends on the water temps and how close the warm water is. That varies a bit from year to year. Generally, tuna are within range of the recreational fleet between sometime in July and sometime in October. Typically we are fishing in 3000'-6000' of water - e.g. off the edge of the shelf. That's usually about 45-70miles (72- 112km). Farther south at the S. end of Washington state, the shelf is a bit closer and the warm water and tuna come in a bit closer (anywhere from 25-45miles). Also, on the N. end of Vancouver island the shelf is a bit closer. Regardless though, you need a boat with plenty of fuel and a range in excess of 120miles and preferably much larger. I typically burn about 100gal of fuel per trip and do 60 miles out and back (120 miles total) + another 60-100 miles of trolling (6-12 hours at 8kts).