You could spend $500 bucks on a combination chartplotter/fishfinder, or you could spend $5,000—and there’s a world of difference between “inexpensive,” and “cheap”. How can you make an intelligent choice as to which unit best fits your needs and your budget? Make sure you consider these five important factors, before you pull the trigger.


1. SIZE MATTERS when it comes to the screen, because this dictates from how far away you can see the unit, how large the numerics will be, and how “squeezed” the screen will become if you use a split-screen or zoom function. Look for units with screens that are at least 5” diagonal, or larger. Anything smaller then this is going to be tough to see unless you’re hunched right over it.

Another important screen feature is resolution, which will determine just how much detail the unit can provide. Resolution is measured by the pixel count, with more pixels being better. Cheap units provide only a few hundred pixels by a few hundred, but you can easily find inexpensive units with 480 by 480 or more. And also check out the screen’s visibility when wearing polarized sunglasses. Many will fade when viewed from an angle in bright sunlight. To test this out in the store, bring a bright spotlight and your sunglasses with you when you shop. Hit the unit with the light, put on your glasses, and see if you can still see the screen as you lean off to one side.

2. POWER is another factor you’ll need to consider. But power is only one half of the equation that determines how deep and accurately your unit will be able to detect fish; transducer choice also plays a huge role. More on this in a moment, but first, note that units in the low end of the price range usually put out between 100 and 300 watts. (Remember to check the spec in RMS, not “peak”). If you’re fishing in water of 200’ or less that’s plenty, but if you need to reach bottom in deeper waters, additional wattage will help you punch through.

3. TRANSDUCERS need to be considered in concert with power. The larger the transducer crystal is, the more focused its beam will be. The more focused the beam, the deeper it will penetrate. Think of it like a flashlight beam: one that’s set to spotlight penetrates farther then one that’s set to floodlight. In real-world use, doubling the transducer crystal’s diameter has the same effect as quadrupling the output power. So a machine pushing 300-watts through a four-inch transducer will see just as deep as a fishfinder pushing 1,200-watts through a one-inch transducer. Unfortunately, depending on where you buy the unit you may not have a choice as to what transducer comes with it. In most cases, however, you can easily purchase an upgraded transducer. Airmar’s web site ( has a lot of good info on what transducer upgrades are available and how to choose between them.

4. CONNECTORS may not seem like an important part of the machine, but they are. Connectors with flimsy plastic collars or thin metal prongs can get broken or bent, and replacing them can cost a large fraction of the unit’s price. So wiggle, push, and prod at them in the store to see just how tough they are, before you buy a unit. Pay special attention to these parts if you have to pull the unit off the boat each time you go home, because the more often you remove and replace the plugs, the more likely it is a problem will arise.

5. LONGEVITY is, of course, another important consideration. Water resistance, especially if you’ll be mounting the unit on a small, open boat, is the most important consideration in this regard. Pay close attention to the IPX (International Protection code) or JIS (Japanese Industry Standard) ratings, which are essentially identical. A rating of four is considered “splashproof,” which could accurately be interpreted as “will fry when wet.” A rating this low is simply insufficient for a small, open boat. An IPX/JIS of five means the unit can withstand low-pressure jets of water, six is high pressure jets of water, seven is submersible for up to 30 minutes at three meters, and eight can be operated while submerged continually. Obviously, the higher the rating number is, the longer your unit will survive in the marine environment—and that makes all the difference in the world, between “inexpensive” and “cheap”.