12 inch gps fishfinder combo
This will enable you to use the 200 kHz high frequency frequency to read shallow water. It will also give you intimate details about the bottom. You can probe the depths of the ocean using the low frequency (typically 50 kHz).
Find a chartplotter and fishfinder combination that meets all your connectivity needs. It is unlikely that an older boat will be rewired with NMEA 2000 backbone. You won't need that ability in the chartplotter that you purchase.
Because you will only need to learn how to operate one unit, the learning curve for operational operations will be shorter. The downside to a combination unit is that you now have all your marine electronics in one place.
The speed wheel is another transducer accessory. This paddle wheel supplies water speed to the display unit. These paddle wheel units have been proven to be inaccurate and susceptible to failure. If possible, we would choose a transducer that does not offer this option.
All combination sounders have the ability to measure water temperature. This is useful information to determine if you are riding in a channel in open water. For large pelagic species, such as marlin and tunafish, fisherman often use small temperature fluctuations to identify pockets of water.
Cartography should be considered before purchasing any chartplotter/fishfinder combo units. You might have a specific brand of chartcard or can trade it up.
Before you buy any chartplotter/fishfinder combo unit, consider cartography. You might be able to trade in or already own a particular brand of chart cards. If you depend on your sounder for important depth and composition information or, even more importantly, if you fish, you will find the most useful combos where the maker has correctly integrated a fishfinder.