The Garmin 198C we tested came equipped from the factory with an external GPS antenna/sensor, an integral 500-watt sounder, and a dual-frequency transducer. It has an internal world map built-in to memory and uses Garmin BlueChart cartography to enhance map details.
The display unit case is just over 6-inches high, 6-inches wide, and nearly 4-inches deep.

Garmin 198c
Wiring for power, interface, and transducer leads hooks to the back of the unit with a single multi-pin twist-lock connector. The transducer branch connects to the transducer with another inline twist-lock connector.
A factory installed connector on the display unit end of the antenna cable makes connecting it a snap. Also, the 198C has tapped holes in the back of the case to facilitate flush mounting. Installation was simple and straightforward.
Screen Size and Viewability
The Garmin 198C screen is 3-inches wide and slightly over 4-inches high yielding a diagonal measurement of 5-inches. It has a resolution of 234 x 320 pixels.
At this resolution details are not as sharp as they appear on newer high resolution screens. It has thirteen levels of control for screen brightness and contrast. The brightness control range was adequate and the contrast control effective.
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Two color palettes, sun or dark, can be selected from the map tab on the main menu. In daylight conditions, it showed some screen darkening when viewed with polarized sunglasses. Some intermittent screen fogging was noted in the center of the screen. We rated the screen good for both daytime and nighttime viewability. Pushbuttons and the cursor pad are backlit.
Operation
Most functions on the 198C are controlled through multi-layered menus. Hitting the menu key twice brings up the main menu with a long list of items in tabular format on the left side of the screen, selecting a tab opens another menu page where you can make and execute selections.
Waypoints
Waypoints can be saved at the boats position by pressing and holding the enter/mark key. This brings up a data box with waypoint





