I'm sorry John, but there is no way your 13.5 ft boat is keeping up with any of my longer boats. Some people may want to just tootle around at slow cruising speed whenever they are out, but what if you want to get out for a bit of exercise and cover some distance?

I'd be surprised to see many folks that paddle cruising kayaks at 5+ knots for extended periods - but perhaps your crowd is a lot fitter than mine.
Here's the track for a little 3 day solo trip I took last summer in my 13.5 foot Coaster - with food and water for a week on board as well as the usual camping gear (the weather was rainy and I cut the trip short).

The distance between tick marks is a nautical mile. It's too small to see the legend to the colour coding here, but the speed was mostly in the 3.5 to 4.5 knot range.
I wasn't working very hard, but I did cover a reasonable distance each day - it's pretty typical of the sort of paddling I do with friends. Without gear in the boat (day paddling), I would have been faster by perhaps a half knot.
BTW, the reason I took the Coaster instead of one of my longer boats (Panthera, Mariner Max) : I knew the Coaster would be much better if I got into rough conditions. BTW, our NDK Romany (similar to a lot of the popular strip-built designs we discuss here) would have been much slower.

The 'longer boat is faster' idea just doesn't work for most paddlers. Check out the page at OneOcean which discusses this:
http://www.oneoceankayaks.com/kayakpro/kayakgrid.htm#totalanch

For the boats in that graph:

The StormSLT has the lowest total resistance across the entire speed range making it the ideal cruising kayak for lighter paddlers with less physical strength.

Here's another page with some info:
http://gnarlydognews.blogspot.ca/2011/02/kayak-lenghtspeed-and-stability.html
From that page:

It seems that the shorter kayaks have less resistance than the long ones, at recreational/Club speed.

Those graphs predict speeds on flat water - in choppy and windy conditions, the shorter boat with less wetted surface might have even more advantage, since the paddler won't be fighting to keep the boat going in the desired direction.

About my 13.5 foot Mariner Coaster:
From the marinerkayaks.com page (where there is a lot of info on kayaks in general, and kayak technique and rescues):

A small wetted surface and a prismatic coefficient that maximizes the effective waterline length makes it easy to maintain cruising speed of four knots or more in a Coaster (top speed is over five knots). Small paddlers love it because they easily keep pace with larger companions who had previously left them behind.

From the SeaKayak magazine review of the Coaster:

The Coaster is quick to accelerate to cruising, speeds. ST notes that in the Coaster she can keep up with stronger paddlers. DM pushed the Coaster to 5.17 knots for a mile at maximum effort, 4.9 knots for over an hour, and 4.6 knots in rough water. CC reported she could keep a 4 knot pace.

That's one reason it's very difficult to find a Coaster on the used market - owners don't want to give them up, and when they do, they usually find a buyer without needing to advertise.

And, we haven't even talked about Prismatic Coefficient and speed..... A boat that 'looks fast' (long and pointy) won't necessarily be so, without a powerful 'engine'.