I am an aircraft engine lover, and the only one I know on a 14 footer is fine with a single axle. However, there is a seismic job running nearby. They have 17 boats so far. Most are 14 and 15 footers. Only one 350 and it is sitting on a single axle. There rest are 454s with powershift props 2 and 3 blades. I think about 5 or 6 of those are single axle and the rest on double axles.
I agree with Cracker, and if you can afford it, get the double tire jack stand. Can roll it in the gravel a lot easier than a single tire.