Lowrance Mark-4 Specs:
Display: Grayscale 320x240 (H x W)
Sonar Frequency: 83/200 kHz
Sonar Depth Max: 1000 ft
Waypoint Storage: 3000
Waterproof Rating: IPx7
Power Supply: 12 vDC
Input Power: 12-17 v
Cable: 20 ft
I was pretty excited to use this fishfinder, since it had the GPS integrated into the unit. The install went well - the stock bag of screws and bolts/nuts were used in mounting this unit to my kayak. Setup was easy - the first power-up asks you some setup questions and you are ready to roll.
The button layout on the front is relatively simple - it will interface the menus pretty easy. The only thing I really messed with is zooming in on the GPS map, and setting waypoints. I didn't do a lot of offshore with this unit, so I didn't get to program any kinds of coordinates into it. I liked being able to see my track on the map, and being able to back-track along the same path. This came in handy when I was moving along and noticed shallow areas that could have given me problems on the return trip to the launch. I could also mark spots where I was catching fish too.
The Mark-4 has a grayscale screen - it isn't too hard on the eyes. I usually keep it in split-screen mode (map and sonar on the screen at the same time) but it also has the full-map page, sonar page, and a compass/heading page along with the dual-view mode.
The Mark-4 has a slot on the bottom of the unit, covered with a rubber flap, that is for a micro-SD card. You could put a Navionics chip inside the unit and have even better maps to use. Although the Navionics maps are pretty sweet, the base maps included with the Mark-4 aren't too shabby.
The power cord and transducer share a plug going into the unit. There is another port plug in the back of the unit that is unused for a basic setup - you might want to dab a bit of silicone to cover that socket up - the leads will corrode over time - especially with use in saltwater.
Ram makes a adapter for the Lowrance units that fits the head-unit to a 1" Ram ball, which you can put on various Ram mounting products. I use a system like this to put it on my Hobie Outback.
One thing I didn't like about the Mark-4 is the little rubber flap on the bottom, that covers the micro-SD port. That little flap loves to pop-open, and sometimes it will fall off. This cannot bode well for the unit if the cover comes off and it takes a bath in saltwater. I wish Lowrance would improve this for future updates.
The Mark-4's power cord didn't include a inline fuse. Seems like this should be standard equipment for all fishfinders straight from the factory. Make sure you add one just in case something shorts-out.
The Lowrance Mark-4 is a nice little fishfinder/GPS combo, and the least-expensive GPS fishfinder I could find on the market. The small screen handles the map and sonar split-screen sufficiently, especially if you'll be in a close-range viewing situation - like a fishing kayak or small boat. If you don't mind the grayscale - then this is your unit. If you want color - pluck out the extra dough for the Mark-4's color cousin: The Elite-4.