Nice building and a very good idea to have one to keep a boat out of the weather. I am a former carpenter and have a few things to add to the discussion. (I retired early from carpentry so I could do something easier on my body so now I'm a firefighter - smooth move ::) )

Whether it's a pole shed or elaborate garage, you need to start with a proper foundation. Knowing your local soils and how to prep the footings is the first thing or you will pay for it later. The local building inspector should be able to provide info on this that is applicable to your area. Soil contact and wood is asking for trouble as well. You all have some nices boats, may as well do the storage building right. A lot of info on building construction is available online to help you along the way. I frequent a diy builder forum and there are some novices building small houses that are really amazing. It's not rocket science but it takes attention to detail. Remember: flat, plumb, and square.

I see alot of incredible work being done on the boats here and there is no reason you guys can't build a storage shed for the boat yourselves if you want to. Although you have to decide if the time and effort is worth it vs. paying a professional. Be aware that there are alot of people portraying themselves as professionals out there that are far from it. Sort of like the auto tech trades nowadays - you have to look to find a good one. I've seen some work that I don't feel comfortable even walking through the door - makes me queasy really :o (I know, I'm anal)

Suggestions on design: build it with taller rollup door than you think you need and install another one at the opposite end. This will allow you to drive in one end, drop the trailer and drive straight out. That's the way mine will be!! ;D Or if you have a dedicated hauling vehicle, build it long enough to leave it hooked together during fishing season.

Ya gotta have a garage!!!