Surfing Waves

Help please...
I have a 6'4" Quiet Flight thruster w/ 3 glassed in fins...Tom Nielson design. Probably a 1990 or so....
measurements written on the board are:
11 1/4
x
18 1/2
x
13 3/4
"Double Concaves"
"2114 (1x3)", too...but i don't know what that means. What do the dimensions above mean also?
Where are the three measurements taken?
I weigh 145 and am 5'7"...great board from home in Florida, but now I'm stationed in Guam, and it's all reef break. Been ripping on this one, but it's outdated. I'm having a hard time getting the board to finish turns unless I'm standing on the very tail. i surf pretty aggressively, with a lot of driving turns and fast runs. need to know what to look for in a new board. this one doesn't whip turns around fast enough...wants to try to go straight as I come around. was going to shorten the #3 fin, or the 2 twin fins....which would do the trick? I'm thinking the center fin...
Help! the waves here rock!
Brian

What kind of tail is it? A rounded square tail is good as it releases quickly in turns. I find when I ride my semi-gun with a rounded pin that it holds well in turns but they are hard to get out of as quickly as with a square tail.

The 18 1/2 is the width of the board the 2114 is probably the serial number the shaper uses. One measurement that is missing is thickness, all those numbers you've mentioned are too large for thickness. To give you an idea thickness is usually represented like this: 2&5/16" or 2&1/2".

Are the dimensions easy to read? The 2114 might be 2&1/4 which would be the thickness?

So usually a board's dimensions are presented like this:
6'0 x 18&1/2" x 2&3/16.
So that's length, width, thickness.

When there are extra measurements they usually are for the tail and nose width. The 11 1/4 and 13 3/4 could be for nose and tail width respectively.

If you want a looser board start with the centre fin, or just get smaller ones all around. If you get smaller ones you'll probably lose a little drive.