Best Portable and Mounted Fishing Depth Finders for Fresh & Salt Water

A beautiful sunny afternoon, you’re steering your boat out of the bay. The shores float by, the familiar cawing of ever-watchful seagulls lulls you to sleep… The next moment, your peaceful day comes to a grinding halt as you bump the ground.

Statistically, people mostly run aground on nice, sunny days. Summer might as well be the season of accidental groundings.

You can (and must) take some basic precautions to keep your boat off the ground in unfamiliar waters. Still, basics can be insufficient. You shouldn’t expect the charts to be 100% accurate, your safe speed may be not so safe, and counting on buoys to be everywhere you need them is inviting trouble.

How to make your boating experience safer, then? Well, you can crawl ahead and cast the lead every now and then, like in the Good Old Days. But why bother with old-fashioned methods when a single depth finder can save you a lot of trouble — and money.

So, what depth finder should you get so that you don’t miss out on any critical features? Don’t worry, we’ve already done the boring part. Just sit back and relax our review on five best depth finders.

Top 5 Best Depth Finders for Newbies and Pros

A depth finder cannot save you from a collision, but it will shut down the possibility of running aground as long as you take precautions. That’s definitely worth a hundred bucks or two.

Aside from that, a depth finder is a must-have for an angler. Even a simple depth finder without a CHIRP sonar can be of help. Different fishes live in different depths, and the knowledge of how deep is the water under the keel makes a huge difference.

That said, if you like your quality time with a fishing rod, consider getting a fish finder. You can use it as a depth finder, and even the cheapest fish finder is packed with amazing features and more advanced than a dedicated depth finder.

Before we do anything else, let us say something: not all products on this list are dedicated depth finders. We have three depth finders, one fish finder that doubles as a depth finder and one fish finder/chart plotter combo — and, of course, it is excellent as a depth finder, too.

Why did we do that?

We spent weeks on this research. The first thing we found out was that 16% of our readers don’t know the difference between a depth finder and a fish finder. Some people punched in search queries for depth finders when in fact they were looking for a fish finder or an even more advanced device. The others were apparently searching for a fish finder, but they were looking for just a depth finder.

Indeed, fish finders and depth finders are often presented as the same thing. But they aren’t. That is why we aim to review the best three depth finders and cover two extras for those who hit this review by mistake.

1
HawkEye DepthTrax 1B — High-Speed Depth Finder

If you like speed, you should definitely look into the DepthTrax 1B from HawkEye. This depth sounder is capable of providing accurate readings between 2.5 and 200 feet in both metric and imperial units at speed up to 55 knots (63 mph). That is almost twice the max speed of a generic depth finder.

The DT1B is a mounted in-dash depth finder. It requires 12V DС power to operate. You will need to get a separate 12V battery (or a pack of two 6V batteries) if you want to install this depth finder on a boat without an onboard power system.

Dual-Mount Transducer

The depth finder comes with an in-hull transducer. It is not designed for thru-hull installation, but it can be transom-mounted.

Be advised, no adhesive is included with the sounder. You need to buy it separately if you’re aiming for the glue-in option.

Make sure not to order an adhesive that is not two-part and slow-cure. HawkEye’s experts recommend against using them.

You will need a test ride to find out if the transducer is well-positioned after you glue it in, but you will not be able to remove it if the glue cements too fast!

3-stage Warning System

A warning system is one of the reasons to choose a dedicated depth finder over a generic fish finder. Thankfully, the DepthTrax 1B can boast more than just its max speed. Equipped with a three-stage programmable warning system, the DepthTrax 1B can warn you in advance when you’re approaching deep or shallow water.

You will need to be very attentive, though. The alarm will be muted automatically after 10 seconds. The display will still flash, but that’s it.

The depth finder will not be able to give you an alarm if it can’t get a depth reading. That can happen in some very specific situations addressed in our Buyer’s Guide.

Keel-Offset Function

The Keel-Offset function may sound like it’s a super-cool feature for those not in the know. However, it boils down to telling your depth finder how deep your vessel sits in the water. A useful feature to have, but it’s nothing mind-blowing.

You can’t program in a keel offset of more than 20 feet. More than most of us need, but if you’re one of those lucky guys who have a yacht with a draft of more than 20 feet… Why are you even reading this? You probably have a team of experts on your payroll who can do it for you.

Illuminated High-Contrast Display

The monochrome LCD display is not very sophisticated, but it’s large, illuminated and high-contrast. Additionally, it’s equipped with a SoftGlow™ backlight, which does not strain your eyes when it’s dark and allows to see the readouts better at daytime.

The display is to be installed in the dash panel. You can cut a standard 2-inch hole or use a pre-cut hole.

Installation Issues

Most of the issues the users face come from improper installation. Even professional installation is not a guarantee your depth finder is properly installed. If the sounder works at all, chances are, it works correctly. However, if it’s poorly positioned or loose, the results will be disappointing.

Refer to the installation manual before installing the sounder. If you have the transducer professionally installed, make sure the mechanic has checked the manual. It’s true that transducers of the same type are very much like each other, but they do have differences, and disregarding them can have drastic results.

The glue-in option is more likely to dissatisfy you. You should keep that in mind when making a choice. The thickness of the hull has a direct effect of the performance of the transducer, as it only delivers 250W in transmitting power. On the other hand, the transducer is much safer when installed in-hull.

The DepthTrax 1B is a basic mountable depth finder for high speed. It can be used on any boat, but we only recommend it for boats with a dash panel.

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Pros
  • Dual-Mount Transducer. This depth finder comes with a transducer, which can be transom-mounted or glued in-hull. On the one hand, that leaves two other most popular installation options uncovered, on the other hand, that’s two mount options available right out of the box.
  • Keel-Offset Function. The DepthTrax can subtract up to 20 feet from the depth reading to compensate for your vessel’s draft. You will be shown how many feet of safe operating water you have under your keel.
  • Accurate High-Speed Readings. This product can operate at high speed. The maximum speed you can use this depth finder at is 63 miles per hour.
  • Auto-ranging and auto-sensitivity. With these features, you don’t have to ever worry about adjusting the transducer. But those who want to be in control and adore fine-tuning will be disappointed.
  • Glare-Free High-Contrast Display. The SoftGlow™ backlight makes reading the display comfortable at any light conditions and prevents eyestrain.
Cons
  • Requires 12 V switchable power source and a dash panel. Not an issue on most motorboats and yachts, but the sounder will be less convenient to use on boats without an onboard power grid and a dash panel for the face.
  • Automatically muted alarms. While the opportunity to have the signal turned off without your input seems to be a convenient feature, the fact that you cannot change this setting is not.
  • Limited in-hull operation. The transducer is not powerful enough to shoot through hull if it’s more than 1/8 inch thick. Remember to account for the beams and the position of the sounder.

2
Lowrance LST-3800 — Best Dedicated Depth Finder Gauge for Anglers

If you want to obtain even more data than most depth finders can provide, but you still don’t want to go for sophisticated and equally expensive fish finders, the LST-3800 from Lowrance may be your best shot. You should check it out at the very least if you have a limited budget.

This depth finder requires a dash panel for installing the gauge and an onboard 12 V power system for operation. That makes it much less usable for kayaks and other small vessels, but don’t worry, we have other options to explore. For now, let’s check out the most exciting features of LST-3800.

700 feet Limit

The first thing to make it stand out is its max depth: 700 feet. At least, that’s what you get in ideal conditions, realistically, it’s best to count on 600-650 feet. But the same can be said of just about any sonar. And even with this reservation, it takes a lot of transmitting power packed in a typical 200 kHz transducer to achieve a fit like that.

That’s not to say you can’t get a 700 feet reading, you can. There just are many factors capable of undermining a sounder’s performance. You can check out our Buyer’s Guide for more details.

Just one more thing before we get to another feature: power is good for a sonar, and this sounder has a lot of power in its tiny case. It provides reliable readings at speed up to 50 mph.

Temperature Sensor

Obviously, not everyone needs this particular feature. The water temperature has no effect on how well your boat performs.

However, that sort of info is valuable for an angler, especially since you can find a warm or cold current based on such data.                                                        

The LST-3800 is not a fish finder. It comes with a simple 200 KHz transducer (except that it has a temperature sensor) and a simple dot matrix display. It does not provide any graphic representation of the bottom structure and is just incapable of helping you find a shoal. However, the combination of depth and temperature readings can give you a heavy hint on what kind of fish you can catch. If there is any.

And that’s just one way to use that data. It’s also handy if you like swimming or diving, or if your kids do. This gauge will provide you with all the info without having to probe the water with an overboard temperature sensor every once in a while. Just find a shallow spot with warm water and enjoy yourself!

Deep and Shallow Alarm

This is an in-dash depth gauge. As such, it’s equipped with a warning system. While not particularly sophisticated, just a buzzer and programmatic triggers, it serves its purpose well.

You can set both Deep Alarm and Shallow Alarm to be triggered by water depth in the range between 1 and 640 feet.

The alarm is very easy to turn off, but it does not turn off automatically. The latter may be a bad thing in the eyes of some people, but we believe it’s worth it. Call us overcautious, but an alarm is not something that should silence itself. Even if it’s a deep water alarm.

High-Contrast Dot Matrix Display with Simple Graphic Menus

The 64Ă—64 dot matrix LCD display is a step above a simple numeric display. It is capable of rendering simple list menus, and that alone makes it more user-friendly than most depth finders on the market. Aside from menus, it can also offer 3 main pages to cycle. Nothing complicated, just the depth reading, the temperature reading, and the combined Dual Display page, but those pages are there.

The display has a backlight with four light-intensity settings. That makes it usable in most light conditions. The screen cannot boast the same soft clarity as a SoftGlow™ display from HawkEye, but it’s decent, and it does its job nicely.

You can switch between feet and meters, as well as Fahrenheit and Celsius degrees.

Limited Installation Options

The included transducer is transom-mounted, and if you have a different installation plan, you should consider buying a different product. That’s not actually a disadvantage, but it’s definitely something you should know before you buy this gauge.

Alternatively, you can extend your options if you’re ready to pay a little extra.

You can get a trolling motor mount adapter specially designed for Lowrance transom-mount transducers. It’s not free, but it’s cheap. A nice tradeoff for those who can’t go for transom mount but would like to use this depth finder.

Pros
  • Transducer with a Temperature Sensor. The frequency is standard for this type of sonars, but the temperature sensor it comes with makes it really stand out. Useful for a lot of things, but only if you know what to do with the temperature readings.
  • 700 ft Depth Upper Limit. The included transducer is powerful enough to get a 700 feet depth reading in ideal conditions.
  • 60x60 Dot High-Contrast Display. While not a competitor to some of the best LCD monochrome displays, this display can render simple table menus to get to all of the settings.
Cons
  • Requires 12 V switchable power source and a dash panel. Not an issue on most motorboats and yachts, but the sounder will be harder to use on boats without an onboard power grid for the sounder and a dash panel for the display.
  • No “Exit” option. The menu lacks an exit button. It does have timeout settings, and the menu is closed on timeout, but that still makes the interface less user-friendly than it could be.

3
Vexilar LPS-1 — Best Portable Depth Finder

If you don’t have a speedboat or any sort of boat with a dash panel and onboard power grid, you’re probably frustrated with the other depth finders on this list. After all, as good as they are, they are simply unusable without at least some sort of power source. Granted, you can get a 12V battery to power them, but that is extra expenses and hassle.

Enter LPS-1, the best handheld depth finder. It operates on the 200 kHz frequency, like most depth finders, has the upper limit of 200 feet and has a basic numeric backlit LCD display. But that’s not what makes it stand out.

Use on Any Boat

With this depth finder, you can easily make do without a power system on board. Not only that, you don’t even need a boat in the first place! It’s a hand-held depth finder, and as such, it’s more versatile than its mountable counterparts.

The fact you don’t need a boat to use this sonar doesn’t mean you can’t use it with a boat. You can’t mount it, but only because there is no need to begin with.

As a handheld device, you can use it whenever you want to, just put the transducer in the water and viola.

Sure, this kind of simplicity comes at a price. With a mounted sonar, you only have to worry about positioning it once: when you’re doing the mounting. Even then, you can get it professionally installed. You can’t count on that with a portable depth finder: you will have to make sure the device is positioned correctly every time you take a measurement. Otherwise, the readings will be inaccurate.

Make sure to point the transducer end straight towards the target. If you’re taking depth measurements, you need to hold it perpendicular to the bottom to get an accurate reading.

Perfect for Scuba Diving

Are you into scuba diving? If you are, then you can’t overestimate this depth finder’s value. Not only can it tell you how far the bottom is when you’re boating, but it can also do the same thing when you’re underwater. That’s a cool feature only handheld depth finders possess.

It’s capable of so much more than just measuring the distance to the seabed. You can measure the distance to any solid object you want, as long as it’s in the water. It can even be your boat. Just aim the sonar as you would aim a flashlight and get your distance reading.

The LPS-1 can handle water pressure at a depth up to 150 feet. Make sure the device is sealed tight before you decide to test that! It comes with rubber seals, but it’s up to you to tighten the caps against them. Test the LPS-1 in shallow water first.

Suitable for Ice Fishing

If you thought we exhausted all the applications of this depth finder back on scuba diving, it’s time to reconsider that notion. We’ve just got to the manufacturer-determined applications, we’re yet to get creative with this handy little device.

Sure, it’s lacking compared to most on-ice fish finders, but as a depth finder, it does its job perfectly. The 25W RMS transmitting power may not seem like a lot, but it’s more than enough to shoot through the ice.

That said, you shouldn’t expect it to work on any ice. If the ice has air bubbles or is just too thick, trying to measure the distance to the bottom won’t work. It has to be hard ice without impurities.

Bright and Floating

If you’re worried about losing such a tiny device, don’t. Even if you drop it into the water, it’s not going to sink. It’s floating, and it will be super easy to spot thanks to its bright coloring.

Single Reading at a Time

You cannot expect a handheld device to come with a warning system. And, indeed, the LPS-1 does not. It does not even stay on for hours. It is designed to take a single reading each time you use it.

Before you think it’s inconvenient, consider this: if your boat can’t power a mountable transducer, it’s probably not capable of achieving a speed where an alarm would be any good. Either way, a depth finder should not be used as a navigational aid.

However, that single-reading approach is perfect for the battery life. The LPS-1 is powered by a 9V battery, and thanks to the efficient approach, it can last for weeks if you use the device sparingly.

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Pros
  • 9V Alkaline Battery Powered. You don’t need to power the LPS-1 with an external power source, such as the onboard power system.
  • Hand Held. There’s no need to mount this device. You can use it on any vessel, including inflatable boats with no mount points, or even without a vessel.
  • Suitable for Scuba Divers. Scuba divers can use this device underwater to get the distance to the bottom, the surface, or any remote solid object. It’s waterproof up to 150 feet.
  • Suitable for Ice Fishing. The LPS-1 can get a reading through the ice if certain conditions are met.
  • Battery Efficient. The LPS-1 is designed to take a single reading every time you use it. That is a tremendous advantage for the battery life.
  • Floating and Easy to Spot. This depth finder does not sink. That makes losing it a lot more unlikely. Combined with the navy yellow coloring, it’s easy to recover it if you drop it into the water.
Cons
  • No warning system. As a handheld device, the LPS-1 does not come with a buzzer. If you need this feature, we advise getting a mount depth finder, even if you can’t mount it and need a separate battery to power it.
  • Getting accurate readings is hard. You need to keep the depth finder pointed straight at your target. If you fail to do that, you can still get a reading, but the distance will be overrated.
  • Sensitive to cold. For a depth finder capable of shooting through ice, the LPS-1 is too sensitive to cold. You should keep it warm when not in use.

4
Garmin Striker™ 4 — Most Versatile Fish Finder for the Price

If you are unhappy with what a dedicated depth finder can offer you, it’s time to consider your other options. Trust us, you have plenty of them packed in this single fish finder.

It is not a depth finder, but its price is comparable with that of a depth finder. Is it any better than a depth finder? That depends, a depth finder has a far better reaction time. Otherwise, the Striker 4 can give you all the same and more.

GPS and Chart-Plotting

The Striker 4 is equipped with a GPS module but not is capable of true chart-plotting. You can obtain your speed, calculated from the GPS data, and your geo position, however, the Striker cannot visualize it on a detailed map.

Does it mean it’s useless? Of course not!

The Striker 4 may not be able to render detailed maps, but it can render the waypoint map. That alone makes this fish finder worth buying it. You can save or enter waypoints, and the Striker will guide you to them.

No, it can’t autopilot your boat, but it can give you a loud warning if you get off-course.

Advanced Multi-Level Warning System

When you’re dealing with dedicated depth finders, a deep water alarm and shallow water alarms are the best you can hope for. But the Striker 4 is a fish finder, and, what’s more important, it comes with a dual frequency CHIRP transducer with a temperature sensor, and a GPS module. It processes a lot more data than a generic depth finder, and it’s no wonder it is capable of more.

Sonar Alarms

To start with, the Striker 4 can do the basics: shallow alarm and deep alarm. It’s a feature any in-dash depth sounder has.

It also has a temperature alarm. If it’s set, the processor will sound the alarm the moment the water temperature changes by more than 2°F. A useful feature for an angler, although it takes some knowledge to make use of it.

However, if you’re not using the transducer the Striker 4 comes with, it can fail to deliver temperature readings. The transducer must be equipped with a temperature sensor to make it work.

Third, being a fish finder, it’s only natural for the Striker 4 to have a programmable fish alarm. You can set it to react to any fish, but it is also possible to set it to react to large or medium fish only. To ignore the value of this particular alarm is a crime against common sense.

Navigation Alarms

This fish finder comes with three navigation alarms.

You are already familiar with one of them: the Off-Course alarm. If you’re getting off-course, you will get a loud warning.

You can also set the Arrival alarm. As you can guess, it allows you to know when you reach your waypoint. It’s handy, but that’s about it.

The Anchor Drag is designed to let you know when you drift too far away while anchored. You can specify the distance that triggers the alarm.

77kHz/200kHz CHIRP Transducer with a Temperature Sensor Included

These days, a CHIRP sonar is a must for a quality fish finder. By now, even outsiders have caught up. However, such a transducer is definitely an overkill for depth readings.

But overkill or not, it is useful, that’s for sure. The transducer included with this fish finder yields 200W RMS and can shoot as far as 1,600 feet freshwater and 750 feet saltwater.

However, the Striker™ 4 does not come with a high-performance transducer. You will have to by one separately if you want to get the max out of this device.

Flasher Sonar

The Striker 4 has a programmatic flasher sonar as one of its modes. Given that it’s not a real flasher sonar, it cannot boast the same reaction time as a depth finder or a hard flasher, but it can be beneficial for ice fishing and vertical jigging. Other than that, this mode has no real applications.

Mount Options

The fish finder comes with a transom mount transducer.

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Pros
  • Advanced Sonar Warning System. The Striker 4 reacts to more than just deep and shallow water. It can also detect water temperature changes and respond to fish.
  • Navigation Warning System Since it is equipped with a GPS module, this fish finder has 3 different navigation alarms: Off-Course, Arrival and Anchor Drag.
  • Waypoint Map. While it’s nothing unusual for more advanced devices, for a fish finder that’s an outstanding feature, especially compared to depth finders.
  • Flasher Mode and A-Scope. Both are less graphic than the standard visualization mode. However, the sonar visualizes the data faster. Good for ice fishing and vertical jigging.
Cons
  • Slow reaction time. The flasher mode gives the feel of a real flasher sonar, and they are known for their instant readout, much like depth finders. But don’t let yourself be fooled: it’s just a visualization. It is much faster than usual but still slower than a depth finder.
  • Mediocre Included Transducer. The Striker delivers good results right out of the box. However, you need a separate high-performance transducer to get the best out of it.

5
Raymarine Dragonfly 7 Pro — The Most Advanced Imaging Fish Finder that Doubles as a Depth Finder

Sometimes, customers want to get the most advanced product money can buy. Is the Dragonfly 7 Pro that kind of fish finder? In a sense, yes.

That does not mean there aren’t more advanced fish finders out there, that’s just not true. However, we must draw a line somewhere. We draw it here and now. This is a depth finder review, a fish finder that has ten times the cost of an average depth finder should not be on this list. And it’s not.

As for the Dragonfly 7 Pro, it is fairly advanced, even compared to the Striker 4. It does not penetrate as deep as the Striker but it’s an imaging sonar, and it has a lot more features and sensors. Unlike every other product on this list, it also comes with a WiFi module.

WiFi Module

Android and iOS devices can function as WiFi hotspots. But you don’t need that feature since the fish finder itself is a hotspot.

We’ve been tempted to use the word “Wi-Fish” for this feature. However, it has little in common with the Wi-Fish™. That is another sonar from Raymarine, one that comes without any kind of screen. Its interface is built around a mobile app of the same name.

That’s where the temptation comes from. The Dragonfly 7 Pro is perfectly compatible with the Wi-Fish mobile application. Unlike the Wi-Fish™, the app is not the only way to control the sonar.

The Wi-Fish application comes with augmented reality features, which makes it more interesting for Dragonfly users, who don’t need it to provide them with basic info.

But the WiFi module is not what makes it valuable. It just makes it a cool toy.

DownVision™ Mode

In our opinion, the DownVision™ feature is one of the reasons to choose this fish finder over anything else on this list. If you don’t need DownVision™, you should reconsider buying this product. You probably won’t need all of its features.

DownVision™ generates a wide-angle side-to-side beam. Unlike a typical conical beam, it covers the area directly under the boat and a little to the sides.

That allows the Dragonfly generate photo-like images. It’s imaging capabilities work up to 600 feet. That’s less than the Striker, but the quality of the image itself is definitely superior.

The DownVision™ mode is not well suited for high speed, it’s better to use the typical conic beam for that. It uses a typical dual-channel CHIRP sonar for that.

2X GPS

The GPS receiver is twice as reliable as a standard module. It is possible thanks to the dual channel hardware: the receiver can use both GPS and GLONASS signals to calculate the position.

GLONASS is not just the Russian alternative to GPS. It is just as global as GPS, but unlike GPS, it is more suitable for high latitudes. Also, GLONASS employs different satellites. What does that mean for you? Actually, it matters little on water, but inshore where tall building can obstruct the signal, GLONASS can take over when the signal from GPS is lost, and it works both ways.

Chartplotter Combo

If DownVision™ isn’t going to cut it, then the fact it’s also a chart plotter should. If you don’t need this feature either, then you don’t need the Dragonfly. You can spend your money better.

It’s definitely more capable than the Striker, but it’s also more expensive, so that is to be expected. You can use it with Navionics® charts, LightHouse™ charts, and C-Map charts by Jeppesen®. The Dragonfly can also generate bathymetric charts on the fly based on the sonar data.

It comes with a waypoint map, but it’s just a nice bonus compared to the other features the Dragonfly can boast.

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Pros
  • Wi-Fi Module. It’s not an essential feature, but it’s certainly interesting to use. Makes a good toy out of the sonar, but its screen is more than enough to provide you with all the info.
  • GPS and GLONASS. The fact those two global positioning systems operate on different satellites makes navigation twice as reliable.
  • Chartplotter. The Dragonfly is also a chart plotter. It is capable of everything a chart plotter can do, including generating its own bathymetric charts.
  • DownVision. The most useful feature for those who need to obtain information on the bottom structure. DownVision can give you photo-like images based on the dual-channel CHIRP sonar.
Cons
  • Price. The price is not high for a fish finder. But while the Dragonfly is a quality product, you will have to pay for that quality. If you need a depth finder, and you don’t need a chart plotter's most essential features, you should buy something else.
  • Slow reaction time. The Dragonfly comes with the A-Scope mode, which is much faster than the normal mode, but it’s still slower than a depth finder.

Buyer’s Guide

Things to pay attention to

Reaction time

One of the reasons to choose a depth finder over a fish finder is the former’s reaction time. A fish finder can extract a lot of data from the sonar signal. However, it requires a lot of computational power and time. A typical fish finder is slower than an average depth finder.

Maximal Depth

The deeper, the better, but only if you need that. If you want a depth finder for safe navigation, 200 feet is more than enough. But if you’re fishing, you need all the data you can get. A fish finder is better suited for that, but if you only want a depth finder, get one that can reach as deep as possible.

Mount

Many mounting options exist, but you cannot plan for all of them. It’s up to what kind of vessel you have.

Thru-hull is the most challenging. We don’t recommend to plan for this option unless you know what you’re doing or have consulted a professional mechanic. If you do think about this option, you will probably need to buy a thru-hull transducer.

The transom mount is one of the easier options. However, your vessel must qualify. If the transom angle is between 3 and 20° and the hull deadrise angle is not above 30°, you’re good to go

The in-hull mount is best for speedboats and trailer boats. However, the transducer will be severely limited by the hull’s width.

If you have a choice between transom-mount and glue-in mount, we advise going for the former. Sonars perform well with both installation options. However, the glue-in option is permanent.

Trolling motor is exactly what it says on the tin. If the transducer is installed inside the trolling motor or clamped outside, that’s what it is.

Sonar Cross Talk

Although side-by-side work of sonar devices can be possible thanks to advanced algorithms, you must be aware that sonars can interfere with each other regardless. That sort of interference is known as sonar cross-talk and is sometimes referred to in depth finder manuals.

Depth finder transducers often run on 200 KHz (nevertheless, it can be a different fixed frequency). If you have another sonar that runs on the same frequency, consider changing the frequency of one of them. If that is not possible, try to move the transducers as far away from each other as possible.

Even then, both sonars can give inaccurate readings for those depths where their sonic beams cross.

Underperformance Factors

If the bottom is very soft or weedy, the energy of the sound wave will be absorbed, and there will be no echo to register.

The same thing will happen if the water under the keel is too deep, and the dirtier it is, the sooner that happens. If it’s extremely dirty, the sonar may not work at all.

A fish shoal — the thing a fish finder is designed to detect — is just one of the obstacles for a depth finder.


Finally, if you’re going too fast, your depth finder will not be able to give an accurate reading — or any reading, for that matter.

Combined, those factors can severely limit the performance of your depth finder. That is one of the reasons you shouldn’t use it as a navigational aid.

Questions and Answers

Study the nautical charts of the area, maintain a safe speed, look out for obstacles and danger buoys — those are the basics. A depth finder will be of help, however, you should not treat it as a navigational aid. We recommend using a chart plotter and any side view sonar.

Yes, but only if some of the underperformance factors are at play. If you can’t get a depth reading and you have reasons to believe it’s not due to the fact how deep the water is, consider taking extra precautions. Do note, a CHIRP sonar is more likely to return a reading than a simple broadband 200 kHz sonar.

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