Lead core line is one of the simplest ways to get a lure down to fish without downriggers or heavy weights — and the colors aren’t just for looks. Each color tells you how much line is out, which tells you roughly how deep your lure is running. Here’s how to read it.
What lead core line is
Lead core is a braided or woven line with a soft lead wire running through the center. That weight makes it sink as you let it out behind a moving boat. The line is dyed in repeating 10-yard segments, each a different color, so you can count how many segments — “colors” — you’ve deployed.
The “rule of fives”
The classic rule of thumb for standard 18 lb lead core is about 5 feet of depth per color at a trolling speed near 2 mph. Each color is 30 feet (10 yards) of line, so a full core of ten colors is 300 feet of lead. Let out five colors and you’re running roughly 25 feet down; let out eight and you’re near 40 feet.
Speed changes everything
Depth per color is not fixed — trolling speed has a huge effect. Slow down and the line sinks deeper, up to five or six feet per color. Speed up and the line planes higher in the water, averaging closer to two or three feet per color. Even a tenth of a mile per hour makes a measurable difference, which is why consistent boat speed matters when you’re trying to repeat a depth that’s producing fish.
Counting colors as you go
Let line out steadily and count each color change as it leaves the reel. Many anglers note the depth a fish hit by remembering how many colors were out, then return to that exact count. Adding a monofilament or fluorocarbon leader between the lead core and the lure keeps the heavy line away from the bait and gives a more natural presentation — just remember the leader adds a little extra depth and distance.
Standard vs thin lead core
Newer thin-diameter lead cores cut through the water with less resistance and sink faster — often around seven feet per color instead of five. If you switch line types, your old color-to-depth math changes, so recalibrate rather than assuming the same numbers.
Estimate your depth instantly
Skip the mental math on the water. Our free trolling depth calculator turns colors out, speed, and line type into an estimated running depth in seconds — a great starting point before you fine-tune with a depth finder.
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