How To Determine Trolling Weight To Depth Ratio

The most efficient way to cover a large area of water in the quickest amount of time or the most thoroughly is by trolling. Nothing else is going to get you more fish in a shorter amount of time except maybe using dynamite.

Trolling weight to depth ratio is an important concept to understand before you get started. Books have been written about how to determine trolling depth of your baits, but we’ll break it down here into simple information you can learn quickly from.

Learning how to use downriggers can really help inexperienced anglers to catch more game fish in deep water. Downriggers are not cheap devices and they are not very effective for smaller boats or kayaks. This guide about trolling will help you understand the various ways you can figure out what depth your bait is at so you can target big game fish in a reasonable amount of time.

Your boat’s sonar will tell you how far down the fish are, now how do you get your lines and bait down to that level? You’ll need to use a downrigger, an automatic one that costs a lot of money. The alternative is to use a hand cranked downrigger and then you’re going to be hating life and not loving fishing like you should!

Trolling Weight to Depth Ratio

The ratio between weight you are using to hold the rig down at a certain depth and the depth your baits are reaching is not a steady number.There are many variables at play that all need to be accounted for in order to judge the ratio of weight:depth.

Factors Involved in Trolling Weight to Depth Ratio

  • weight of the rig itself
  • weight of lead to hold down the downrigger
  • thickness of wire or chain attaching the downrigger to the boat
  • thickness of fishing lines used
  • length of fishing lines and number of lines out
  • types of lures or bait used and amount of drag created by each
  • current strength
  • speed of boat
  • depth of water – the deeper the water, the more resistance 

How Can You Calculate Trolling Depth?

You may know how deep the fish are, but you won’t have any clue how deep your baits are running unless you clip a depth gauge on them. Lucky for us there are a number of tips and tricks we can use to figure it out.

For the first couple runs you should drop your lines around the depth you know the fish are at, and slightly higher and lower to cover a little greater range.

Captains experienced with trolling can sometimes estimate closely how to adjust the downriggers for proper function. This comes from years of experience with the gear on the boat. There is often dissension among anglers in the party and it will take some experimentation to figure out the best troll depth for the rig.

One way some people get started is to drag your lines far out the back and down deep into the water column, even deeper than where you know the fish are. From there you can adjust the speed of the boat to see at what speed you get strikes on your bait.

There are a number of ways to set up your gear for trolling at a certain depth. You’ve got to find out how to do that efficiently without wasting too much time. Here are some tips you can use that captains have been using for decades.

You may use any of these, or a combination of any of these. The decision is yours and it’s a matter of what you feel most confident going with. The proof that you’re at the right depth will come with the number of fish you catch while trolling. Got it? OK, let’s get started!

Using a Shelf or Thermometer to Find Out Trolling Depth

To find out how deep your lure will go with a certain rig and length of line here is one rather risky way you could go about it that you probably shouldn’t try but captains do it all the time.

The not so recommended way to do this is to find out where a shelf or edge gradually gets shallower. Start dragging your rig with all the lines and bait on it that you want to use in the deeper area and gradually come toward the shallower area. Once your baits start bouncing on the hard or soft bottom you’ll know what depth they are at from the sonar profile of the bottom in that area.

The problem with this method is that you can snag your rig on something substantial and lose the entire thing and possibly damage your boat. Submerged debris could ruin your day!

Using a thermometer can be a safer and somewhat more labor-intensive way to figure out the depth you’re at, but this is recommended over the first one.

Temperature changes in water at different depths of course and you can measure the temperature at various steps before starting to drag your rig with a thermometer attached to a bait line.

At first we will plan a rough guess at how much line you think you will need to let out, keeping in mind how many lines you have, how heavy your weight is, how thick your fishing line is and wire holding the weight. When you get any bite, quickly reel in your thermometer line and see what the temperature is.

If the temperature reads very close to the surface level temperature then you need to let out more line to get deeper. Eventually you will come to the proper depth and know what it is because you have already tested various steps in temperature from the side of your boat.

This will give you a good idea how much line you need to leave out in the back given the weight of your rig and the various variables that need to be accounted for.

Keep letting out more and more line to get your bait deeper – as deep as the fish you are trying to target.

In this way, you’ll know how many lines you can keep out and at what speed you need to drive the boat in order to have your bait reach the proper depth to catch fish.

Winder Counting to Judge Trolling Depth

Penn Level Wind Fishing Reel

This method works well with level-winders and it isn’t hard to do. After using one of the crude methods above to create a baseline to start from you can keep a count of how many times your spool winder moves back and forth across the reel face. This will tell you how many times it needs to do so to reach the same depth again the next time.

This works well because every time you reel in a fish and re-bait and have to get a new bait or lure out there you can just count the number of times the winder moves back and forth as you let out line.

If for whatever reason you don’t have level-winders or a spool winder to count, there are color coded lines that change color every 10 feet that you can use.

A variation on the color codes is that you can mark your line in whatever length increments you choose. Putting paint or nail polish on the line will keep it bright enough to see and it should stay on the line at least for a little while.

Wrapping and tying a small bit of thread around the line every so many yards can also help you figure out how long the line is.

Dropping Baits Lower Without Changing the Entire Rig

While looking on sonar you may find that fish are lower than your baits. They may have moved there or they may have just moved in. Anything can happen, and does, right?

How can you quickly drop the entire rig down a few feet or so without touching the downrigger or any other gear?

Quickly turn the boat into the wind hard then wind it back slowly the other way. Boat speed drops dramatically, but more importantly the relative speed of the rig drops more and all your lines go deeper for a bit. Maybe just long enough to entice some bites.

Ideally, your lines are well over 100 feet from the back of the boat.

You may do a hard left or right or you can turn the entire boat around for a few seconds then turn back around and continue in the right direction. All of these give varying degrees of the same effect and may put you on a bite!

Pulling Baits Across the Current

Troll fishing
Troll fishing

If you want to just cut straight to the quick and get baits down to where they should be almost immediately, you can pull your entire rig in the cross current, at right angles to the way the current is moving.

This can be done regardless of what the current, wind, and sea is doing at the moment.

These are just some of the things you can do to attempt to figure out exactly how deep your bait is getting and whether you’re likely to get bites from these huge pelagic fish, or not.

This is not just a saltwater technique, in fact the first time it was used was on a lake. The second time the technique of downriggers was ‘discovered’ it was in the Great Lakes.

Downriggers can be made for salt or freshwater, make sure you get the right one.

Make sure you spend the extra money and get an electric downrigger. The hassle that a crank downrigger can dish out is not worth it for anyone. Trust us!

Fishing many different waters will teach you a lot of things but it can all change in an instant and confound you. This is fishing! When you think you know it all, it can change. Data points you’ve noticed in the past may not make sense. Keep your wits about you and keep first principles in mind. Things that can’t change are good to pay attention to.

Get yourself a thermometer to clip on to your bait lines. Get yourself a good depth finder and electric downrigger. Listen to others on the boat who may have had experience that will help you figure out the right plan of attack to get your baits down to where you want them.

How Much Weight Should You Troll?

For saltwater trolling you can start with a 10 ounce weight and see how that goes. More lines, more speed on the boat, thicker lines and wire, speed of the tide, and so many things affect the rig. Starting with a medium weight 10 ounce ball should be about right for many situations involving 4 or more lines with bait or lures.

Adding more lead weight to your line or employing a diving device will make the line drop down to greater depths.

How Many Lines Should You Troll With?

How many rods do you have that can target the fish you’re after with the downrigger? How many people are on the boat? If you have a couple of rods go off at once will you be able to handle the chaos? How experienced are the anglers on the boat?

All of these factors and so many more can affect your decision of how many lines should go on your downrigger.

Do you know exactly where the fish are and have a good plan for how to reach them? Or are you spraying and praying? If you want to spread out the bait at different depths you may use more lines than you would if you knew exactly how to reach the fish with your bait. Make sense?

In an optimal setup you should have one bait higher than the others and one bait lower. The number of times we’ve caught fish like this has been considerable over the years.

Final Thoughts 

How many fish you catch while trolling will depend mostly on the bait you’re using and the depth you’re at with your bait. Those two things can mean success or failure. Knowing the trolling weight to depth ratio you’ll need to get your baits down to the depth fish are at becomes crucial. If you’re running a charter boat and passengers are paying good money to be out there with you so you can put them on fish, well success is vital, isn’t it?

Sonar is a great help to know where the fish are. Your buddy’s report from yesterday saying that he found fish at 20 feet deep helps a little bit, but nothing guarantees success until you put bait in the same horizontal plane as the fish you’re targeting.

Use depth gauges whenever possible to give you good data on how deep your baits are running. In fact, use the best gear you can afford if you’re running a commercial operation. It isn’t cheap to do it right but your customers are counting on you to put smiles on all their faces.

Are they smiling yet?!

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Brian Hopkins

Brian is an outdoor writer and the youngest member of our team, but he is extremely knowledgeable when it comes to fishing and different techniques for catching different species. He shares valuable information that the younger generation can relate to. When he is not fishing, you can find him hanging with his friends and gaming on his computer.

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