Features June 2004 Issue

Garmin 188C vs. Si-Tex Combo

In a two-on-one chartplotter/sounder shootout, a pair of Si-Tex units takes on a single Garmin combo machine.

Chartplotter/sounder combo units take up less space and usually cost less than separate pieces. But if the combo breaks down, you've lost two important instruments at once. Not good. Citing this Achilles heel, Si-Tex is pushing a two-unit system sold as the "Dynamic Duo" to give the consumer "the convenience and safety of two dedicated products at the low price of a combo unit." It's a compelling pitch, so we decided to test the product. And a good way to evaluate the Dynamic Duo—which consists of the Si-Tex ColorMax 6 chartplotter and CVS-106L sounder—was to match it against a proven combo unit from Garmin—the 188C. 

The Garmin 188C (left) is well-suited for boats with limited space on the pedestal or cockpit bulkhead. If you have the space, though, consider Si-Tex's Dynamic Duo (center and right)—a separate plotter and sounder combo that sells for about the same as the Garmin 188C.

How We Tested
We mounted the Garmin and the Si-Tex pair to a short section of wood, which allowed us to test them in our shop and out on the water. All three units were mounted side-by-side using the supplied brackets so we could easily rate viewability. We examined each machine on a sunny, cloudless day aboard the test boat, looking at them with and without polarized sunglasses, and giving each screen a day-view rating. While at sea and in the workshop, we examined the map display of each plotter and worked through various procedures to assign ease-of-use ratings. Back at the dock, we sprayed the units with fresh water (all lived up to their waterproof claims) and waited for the sun to set. The night-view rating was determined after checking each at twilight as well as in darkness.

The sounders were only tested for viewability and user-interface (in simulator mode) because PS had already tested the pertinent Garmin and Si-Tex sounder units and transducers for accuracy. (See the January 1, 2004 issue. The performance ratings in shallow, mid-range, and deep-water accuracy were almost even between Garmin and Si-Tex, with Si-Tex having a slight edge in shallow water—Excellent versus Good.)

Garmin 188C
The combination of a powerful sounder and a Blue Chart-capable GPS/chartplotter gives the 188C a wide range of features in a single unit. Operation of both sounder and plotter is done via the same 10 pushbuttons and cursor pad. This makes it somewhat more difficult to access certain sounder controls, like gain and depth, although most people will find that the sounder auto functions work adequately under most conditions.

The sounder portion of the 188C is very similar to the 320C we fully tested last September. It has auto ranging, auto gain, zoom, bottom lock, 16 manual range settings, and a variable range marker. Water temperature and speed can also be displayed, depending on the transducer selected. We rated it Good in all depths. 


To test the user interface of the chartplotter, we used the simulator mode and on-water plotting. The course predictor on the Garmin is a small triangle that also represents the boat. It does give a rough estimate of the boat's course. A single color palette is displayed on the Garmin. We found the bold colors easiest to read when not in direct sunlight. At night, they are very easy to read. Entering a waypoint requires just a couple of button pushes.

Although the Garmin has six main data pages, including map, sonar, compass, numbers, highway, and active route, most users will operate the chartplotter on the "map" page because it shows the most information at a glance. We did most of our testing from this page.

Data blocks at the top of the Garmin's map page can be adjusted for size and data. A long list of data items can be displayed. Sonar returns can also be displayed in a split-screen mode with the map. The size of the sonar split window is adjustable, though with the window set at about 50% sonar and 50% map, both can be hard to see—simply because of the reduced size. Another option is to display full-page sonar with a data window at the top of the page that shows waypoint information.

Viewability of the Garmin is excellent under nearly all conditions. Direct sunlight on the screen does make it more difficult to see, but it is still readable. The screen darkens somewhat when viewed at an angle or with polarized sunglasses.

Si-Tex Dynamic Duo
There are two very good things about having a pair of discrete units instead of a single combination device. First, if one fails, the other will most likely still operate. Second, each unit has its own controls and display. This sounder's nine pushbuttons make control of the gain, shift, range, and A-scope just a finger touch away. We rated the screen good for daylight viewing but only fair at night. It garnered the fair rating because, as we reported previously, the screen partially blanks when viewed from certain angles at night. The background color palette can be darkened in seven levels all the way to black for better night viewing. It's better with the background set darker, but the blanking is not eliminated. Panel lights are adjustable separately. Two features found on the CVS-106L sounder, not on the Garmin, are full-color A-scope and depth shift. Again, this unit was rated Excellent in shallow water in our earlier test. It was rated Good, like the Garmin, in mid-range and deep water.

Course prediction is taken to the next level on the ColorMax 6; the predictor line is fully adjustable. Not only does the line show your intended course, but the length of the line predicts the boat position in the future based on your settings. It's large and easy to see. This is a great feature.

In addition to brightness and contrast controls, four color palettes are available—sunlight, classic, night, and normal. Sunlight, which noticeably lightens the colors, improves the screen viewability in direct sunlight, even surpassing the Garmin, in our opinion. Normal and classic modes are used when the display screen is not in direct sunlight. Classic mode uses C-Map NT colors and is designed to look like a paper chart. Night mode darkens the colors to reduce glare and improve low-light viewing.

As on the Garmin, both the layout and information in the data blocks at the top of the map page can be changed. Hitting the Enter key, followed by another button push or two, will yield a waypoint at the current position, bring up a "Go To" menu, or get an instant range and bearing on anything you select with the cursor.

Viewability of the ColorMax 6 is excellent under all conditions. Using its sunlight palette, the Si-Tex bests the Garmin in very bright light.

On paper, the Garmin outshines the Si-Tex pair in some ways. Garmin has 3,000 waypoints, Si-Tex: 500. Garmin: 500 watts of sounder power. Si-Tex: 300. Garmin allows 40 waypoint symbols, Si-Tex 16.

But numbers don't tell the whole story. As we said in our comparison of the Furuno and Simrad plotters beginning on page 6, "we don't consider the number of available waypoints and routes a significant rating factor, at least when those numbers rise above what any navigator could conceivably use them for." The same goes for waypoint symbols.

The fact that the Garmin has 500 watts of sounder power versus 300 in the Si-Tex is more significant, but as we've seen, the Si-Tex shallow-water capability is excellent.

Here's what else you need to know: For about the same price as the Garmin, the Dynamic Duo provides you with two screens and two sets of controls in two complete and separate units. In our view, performance differences are minimal. The Garmin does this a little better, and the Si-Tex duo does that a little better. The real question: Do you have enough space to install two large screens—and do you need them? If you answer yes to both questions, we'd suggest the Si-Tex Dynamic Duo. If you don't have the space, you won't go wrong with the Garmin a solid, proven machine.


• Garmin, 913/397-8200, www.garmin.com
• Si-Tex, 727/576-5734, www.si-tex.com


Also With This Article
"Value Guide: Garmin Vs. Si-Tex"


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