Well, after looking at the abysmal MPG of the Nissan Frontiers and Toyota Tacomas (real-world numbers of 18-19 mpg highway, what my CRD gets towing a #3500 boat), and enjoying the "special" experience of talking to a couple of dealer sales folks, we've come to our senses and decided to keep it. We'll be shopping for a weight distribution hitch. My trailer is a pole tongue style.
My boat is a 17' Arima Sea Ranger w/ the soft top (looks like this, but with a 90 hp Johnson and 15 hp Johnson kicker):
The boat itself isn't too heavy, maybe #3500 with full fuel, coolers, crab pots, fishing gear, etc... The issue is the height of the trailer, and that it is a single axle. To get my hitch ball up high enough to level the trailer, I had to go with a 10" extra long shank, turned upside down for a 2" rise. This levels the trailer and clears my spare tire, but sticks out so far from the CRD's axle that it creates a big lever and makes the rear end squat more than I'd like (this is before putting a couple of my fishing buddies in the bank seat). The result is that if I go more than a couple mph over 55, I get sway. Now I don't mind driving 55 or less, but I'd like a margin of error, particularly as I tow the boat down grades in the Coast Range. And I also get sway every time a semi passes.
A dual axle trailer would solve this problem, but I don't want to deal with that much headache.
The little CRD has gobs of power for towing this boat, and will hold 50-55 mph up steep grades in the mountain with no problem.