I agree with Tsunami Chuck -- look into folding kayaks or skin on frames. Folders typically are 30% or 40% lighter than rigid kayaks of the same dimensions. The Big Kahuna he suggests is a great boat (my first folder was the standard Kahuna) and it weighs 35 lbs. The kayak is $3500 new but you can find one used on occasion for around $2000. The Pakboat XT-15 is another great folder with similar dimensions and runs around $1500 new -- Pakboat is phasing out that model so you may find good deals on it now. They still make the XT-17 which would work for you too. It's only 44 lbs despite being 17 feet long.
Folders can be left set up all season if you don't want to break them down each time and can be hauled on a roof rack just like any other boat. And they have the plus of being able to take them on vacation as checked luggage and to store them in their duffel bag securely in the trunk of the rental car or in your hotel room. Lots of advantages besides lightness, but the lightness makes them wonderful for frequent use closer to home.
Skin on frame rigid kayaks are even lighter -- I have an 18' one that weighs 32 lbs (wood frame with a urethane coated nylon skin). People are amazed to see me (a 60 something average sized female) carrying it to the water single-handed. There are a lot of people who custom build these around the country, often for less than you would pay for a quality commercially built hardshell.
You can even build your own with free patterns and instructions at http://www.yostwerks.com. A good intro to skin on frame kayaks is at this blog by a well-know builder and designer.
All these boats perform comparatively to hardshells of the same dimensions, in some cases better (folders excel in rough water since they flex with waves rather than fighting them) and they are far more durable than most people realize. I can smash my skin on frame with a hammer and it bounces off the skin.
EZ-Dock modular docks
Wabakimi Canoe Pack
Kayak & Canoe Covers
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