I'm not really an expert at this (yet). Here's my attempt at explanation.
When I look at this, my eyes start at the high contrast sun vs sky or the prow of the boat, and then they follow the lines of the boat. It's a nice pleasant curve. Then my eyes run off the page to the right.
So I bring my eyes back to the center, and they follow the stripes on the sail to the back of the boat. And then off the page again.
This is just the natural flow of how you have the image arranged. I think you could put something important at the spot I marked with a green circle and it would provide a nice focal point for the viewer's eyes.
A framing element is something that acts like a frame and blocks the viewer's eyes from wandering out of the image. The mountains on the left side of the image already do this. If the eye wanders down the front of the boat and off to the left, boom boom boom. Angled mountains break up any easy path out of the frame, and steer the eye back towards the right and down, back to the boat.
If you add something to the right edge that leads the eye around and back to the boat I think the picture will be stronger.
Professional cartoonist John K (Ren & Stimpy and a few other cartoons) wrote up some good info for composition on his blog here:
http://johnkstuff.blogspot.com/2006/11/composition-for-layout-and-bg-artists.html. There are 9 parts, and some of it only applies to cartoons, but I thought most of it was good stuff.
There's a more brief page on composition here:
http://www.galitz.co.il/en/articles/composition.shtml. Written for photos, but it applies.
Hope this helps,
Tourist