Downriggers
How deep is your downrigger ball really running?
Quick answer
Downrigger blowback is the angle the cable trails behind vertical once the boat is moving, and true depth equals cable out times the cosine of that angle. At 30 degrees of blowback with 100 feet of cable out, the ball sits at 87 feet, not 100, because the counter measures cable, not depth.
A downrigger counter measures how much cable has gone out, not how deep the ball actually is. The two only match when the cable hangs perfectly vertical, which almost never happens once the boat is moving and water resistance pushes the cable and ball back behind the boat at an angle. That angle is blowback, and true depth equals the cable let out times the cosine of the blowback angle, published trigonometry rather than a rule of thumb.
The consequence is real and easy to underestimate: at 30 degrees of blowback, a common angle at trolling speed, 100 feet of cable out only puts the ball at 87 feet, a 13 foot gap between what the counter reads and where the fish actually are. Heavier or more streamlined weights such as a pancake style weight reduce blowback compared with a round ball of the same weight like the standard 10 pound Cannon ball, but the angle still has to be read off the rigger, not assumed.
What blowback actually is
Blowback is the angle between the downrigger cable and true vertical while the boat is trolling. It is caused by water resistance against the ball and cable as the boat moves forward, and it grows with trolling speed, ball shape and cable diameter. Reading the actual angle off the rigger's own indicator, or off a marked cable, while the boat is at trolling speed is the only way to know the real number for that moment, since it changes with conditions.
True depth by blowback angle and cable out
At 30 degrees of blowback with 100 feet of cable out, the ball sits at 86.6 feet, which rounds to the 87 feet trollers commonly quote.
Published figure A published engineering, regulatory or manufacturer figure. It does not change because somebody disagrees with it.
| Cable out (ft) | 0° | 15° | 30° | 45° | 60° |
|---|---|---|---|---|---|
| 25 | 25.0 | 24.1 | 21.7 | 17.7 | 12.5 |
| 50 | 50.0 | 48.3 | 43.3 | 35.4 | 25.0 |
| 75 | 75.0 | 72.4 | 65.0 | 53.0 | 37.5 |
| 100 | 100.0 | 96.6 | 86.6 | 70.7 | 50.0 |
| 150 | 150.0 | 144.9 | 129.9 | 106.1 | 75.0 |
| 200 | 200.0 | 193.2 | 173.2 | 141.4 | 100.0 |
True depth equals cable out times the cosine of the blowback angle. Read the angle off your own rigger's indicator, since it depends on trolling speed, ball shape and cable diameter rather than being a fixed value.
How much depth blowback is costing you
The same grid, expressed as feet of depth lost rather than feet of true depth, makes the size of the gap easier to see at a glance for a manual downrigger or an electric unit alike.
At 45 degrees of blowback, 200 feet of cable out loses nearly 59 feet of true depth compared with what the counter reads.
Published figure A published engineering, regulatory or manufacturer figure. It does not change because somebody disagrees with it.
| Cable out (ft) | 0° | 15° | 30° | 45° | 60° |
|---|---|---|---|---|---|
| 25 | 0 | 0.9 | 3.3 | 7.3 | 12.5 |
| 50 | 0 | 1.7 | 6.7 | 14.6 | 25.0 |
| 75 | 0 | 2.6 | 10.0 | 22.0 | 37.5 |
| 100 | 0 | 3.4 | 13.4 | 29.3 | 50.0 |
| 150 | 0 | 5.1 | 20.1 | 43.9 | 75.0 |
| 200 | 0 | 6.8 | 26.8 | 58.6 | 100.0 |
How much cable to let out for a target depth
Working the trigonometry in reverse answers the question anglers actually ask on the water: how much cable to feed out on an electric downrigger to put the ball at a specific depth once blowback is accounted for.
Hitting a true depth of 60 feet at 30 degrees of blowback takes 69.3 feet of cable out, not 60.
Published figure A published engineering, regulatory or manufacturer figure. It does not change because somebody disagrees with it.
| Target depth (ft) | 0° | 15° | 30° | 45° | 60° |
|---|---|---|---|---|---|
| 20 | 20.0 | 20.7 | 23.1 | 28.3 | 40.0 |
| 40 | 40.0 | 41.4 | 46.2 | 56.6 | 80.0 |
| 60 | 60.0 | 62.1 | 69.3 | 84.9 | 120.0 |
| 80 | 80.0 | 82.8 | 92.4 | 113.1 | 160.0 |
| 100 | 100.0 | 103.5 | 115.5 | 141.4 | 200.0 |
Cable out equals target depth divided by the cosine of the blowback angle. This grid inverts the true depth table above and is only as accurate as the blowback angle you actually read off your own rigger.
Frequently asked questions
What causes downrigger blowback?
Blowback is caused by water resistance pushing back on the ball and cable as the boat moves forward while trolling. The faster the boat trolls, the more resistance the ball meets, and the further the cable trails back from vertical. Ball shape and cable diameter both affect how much resistance is created at a given speed, which is why blowback varies between setups even at the same trolling speed.
Does a heavier weight fix blowback?
A heavier weight generally reduces blowback at a given trolling speed because it takes more water resistance to move it off vertical. Shape matters as much as weight, though: a pancake or torpedo shaped weight tracks with less blowback than a round ball of the identical weight, since the round shape presents more drag for the same mass moving through the water.
Do all downriggers show the blowback angle?
Some downriggers include a built-in angle indicator that shows blowback directly while trolling, and others do not. Where no indicator is built in, the angle can be estimated by watching a marked cable or by comparing counter readings against a known target depth, such as bottom, and working the trigonometry backward to find the actual angle at that trolling speed.
Why does my downrigger counter say 100 feet when the ball is shallower?
The counter tracks the length of cable that has spooled out, not the vertical depth of the ball. Once the boat is moving and the cable trails back at an angle rather than hanging straight down, cable length and vertical depth stop being the same number. At 30 degrees of blowback, 100 feet of cable only reaches about 87 feet of true depth.
Does cable diameter affect blowback?
Yes. A thinner cable presents less surface area to the water and creates less drag at a given trolling speed, which reduces blowback compared with a thicker cable under the same conditions. This is one reason braided cable is sometimes chosen over solid stainless wire of a similar test strength, alongside quieter running in the water.
Does trolling speed change true depth even with the same cable out?
Yes. Faster trolling speed increases water resistance on the ball, which increases the blowback angle and reduces true depth for the same amount of cable let out. Slowing down reduces blowback and brings the ball closer to the counter's stated depth. This is why the actual angle needs checking each time speed changes meaningfully, rather than assumed constant for the whole troll.
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Researched, not professional advice. This page is compiled from published engineering and regulatory figures, manufacturer specifications and owner-review consensus, not hands-on testing. Figures described as a rule of thumb are boating convention rather than published standards, and they are labelled that way wherever they appear. Marine electrical work is not house wiring. Use tinned, finely stranded marine cable, size it for voltage drop and for the ABYC E-11 ampacity table rather than one or the other, and put overcurrent protection within seven inches of the battery positive terminal, because everything between the post and the fuse is unprotected. A lithium battery needs a charger with a lithium profile. Never load a boat past its capacity plate, and remember that canoes and kayaks carry no federal capacity plate at all, so their stated capacity is the manufacturer own figure. Wear the life jacket, and treat early season water as the hazard it is: cold water immersion takes your breath and then your hands long before it takes your core.