I had one of those.  I will never own another Wagner product again.  I can't say enough bad about it.

Kim

A kayak is not a big job.  I have a hvlp sprayer but would rather use a foam brush than mess with clean up of the sprayer.

Kim

At 20-28 bucks a quart for varnish, look at the wastage in the hose.

Kim

I have a lot of time behind a Wagner, (buildings, fences, etc) and liked it for what I did with it, which was to apply a single color to large areas where overspray wasn't too much of a concern.

I agree with Mr Kim that it isn't the way I'd want to go on a small boat.

It will probably take you well under an hour to paint a hull or varnish a deck with a foam roller and foam brush.  I recently did a sunfish hull with Brightsides, and I think the entire bottom was taking me about 15 minutes per coat to apply the paint.  Prep is considerably longer, but you'll have to prep no matter how you apply.  Cleanup is a breeze with disposable foam - but cleaning the sprayer might double your application time.

I tried a wagner helping a friend to paint/stain a wood fence. It was a short attempt. It did not go well. I wouldn't dream of using it on a kayak.

A sponge brush and you can finish a kayak real pretty with patience no problem. But I think not wise to try spraying one without lots of practice on other things. It is difficult to undue mistakes.

Get a box of sponge brushes and enjoy to most rewarding part of the build.