Many have used:
U Ship.. This is basically an expeditor. You put the job on the site, and haulers bid. Your request is very complex. You have to ship a boat from Florida to Anchorage AK. (or the PNW)--you have to make that clear. It depends if the boat has a trailer, it is cheaper to have a truck tow the boat on the trailer, than load the trailer and the boat on a flat bed. (Or separate the boat and trailer--transport both, because of over height load, or requiring a low boy hauler. After the boat gets to Seattle, you have to arrange for it to get onto a barge--and be transported. There is the option of overland to AK--but that will be more expensive. A distant (cost wise) is to put the boat and trailer on the Marine highway and ship to a port in SE AK where you can pick it up.
First thing: insure the boat and trailer. Make it clear in your bid, you will only deal with a bonded and insured hauler. I have used U Ship for a boat larger than a C Dory--it was an oversized load, yet it only cost me $! a mile. I found a hauler coming down from Wisconsin in the middle of the winter to Florida empty. I had bought a boat on the Great Lakes. The hauler called me on the cell phone when he picked up the boat, each night, and when he was an hour out. The boat didn't have a trailer, and he had a hydraulic trailer--he could either lunch the boat or put it in the boat yard.
You have to be very specific with any boat hauler, exactly what you want to do and what you expect. A haul to AK will not be cheap. I would not be surprised to see at least $2 a mile and maybe $3--plus costs this time of year. Florida is a center of boat building, so many are hauled out of here. Chances of finding a hauler going empty out of Fl is remote. The best bet is finding who is currently trucking boats like Ranger Tug or C Dory out of PNW and might be coming back empty.
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Joule Yacht Transport is excellent and well respected--but only do continental US.
If the boat gets to Seattle, who is going to put it on a barge for you--and be sure it is properly secured?
Every once in a while one of our Alaska Members is driving back home, and can tow a boat...but Tht will not be an insured boat hauler, and probably would have to be named on your insurance--and perhaps have your boat named on his...