If you are tracking left in an Old Town Loon, check your stroke. I'm betting that you are right hand dominant and that your shoulders or biceps are the first thing to fatigue while you paddle and that you are using a relatively long paddle - perhaps 230 or 240 cm.
Spending some time learning good paddle technique and boat control will improve your fishing. How? Well, for one thing you will learn to read the water better. For another, you'll learn how to position your boat in the best spots for making casts to likely fish-holding structure and cover.
The best way to learn better boat control is 1:1 on the river with a teacher. It doesn't have to be a professional teacher, but as a minimum someone who has been on and around rivers in kayaks for a while. Canoe or paddling clubs are great places to meet folks like that.
There are videos on Youtube as well.
A quick synopsis - for recreational paddling in a 10' boat, the paddle should enter the water with the front of the blade perpendicular to the boat and at about where your knee is. You should have to lean forward, twist your tummy to push your shoulder forward, and reach your hand out to do this. It's a lot like throwing a jab. If you have a short shaft on your paddle, the blade will go in the water close to boat and the shaft of the paddle will be on a steep angle of roughly 60 degrees. If you have a long shaft on your paddle, the blade of will go in the water further away from the boat and the shaft will be on a less steep angle of roughly 20 or 30 degrees. When you do the stroke, keep the face of the blade perpendicular to the boat, untwist your torso to a straighter position, sit up, and pull with your arm so that your elbow bends. Those are listed in order of importance. Your stomach and back have a LOT more to do with a good paddle stroke than your shoulder and biceps. When the blade of the paddle in the water reaches your hip, it's time to take it out and repeat the stroke on the other side. When you've got that down, start to apply force to the opposite foot (stroke on right side of the boat, push with left foot). See if that doesn't help your tracking.
This is especially important if you have a long paddle. When you have a long paddle, the blade is angled in the water more, and it is further from the side of the boat when you apply power. Now, think of physics. Your butt is basically the center point of the kayak. If you apply forward pressure off to the side of a swivel, what happens? The boat turns. Theoretically, the boat will turn the same amount the other direction when you do the stroke on the other side of your boat. But, if you are using mostly arm and shoulder strength rather than nice bilateral torso and back strength, and if you are right hand dominant, you're going to apply more power to the blade when you stroke on the right side than when you stroke on the left side. So you turn left.
Spend some time working on getting a good, smooth, equal, bilateral forward paddle stroke, and you will be able to make any boat go where you want it to go whether or not the boat "tracks" well, and regardless of whether the boat has a natural tendency to turn one direction over another.
For what it's worth, I consider tracking to be among the least valuable of boat characteristics and have specifically selected a boat that does not have good tracking characteristics. This allows me to catch eddies better, and make my turns later when approaching a ledge - giving me another cast or two at the push water before I have to begin setting up for a chute.
- Big D