Need some fishfinder input

Im pretty new  to the kayak fishing but after a half dozen trips of bieng out on the water ive decided i would like to have a fishfinder onboard. I've never been in the market for one so are thier anyones to stick clear of? Im planing on doin just day trips, and already own a garmin montana gps so i dont think i need a combo ff/gps. Any one have some good recommendatios?

Hi. I'm new to kayak fishing also. I am a bit electronically challenged. I bought a Hummingbird PiranhaMax 170 with a dry cell battery. Around the battery I bought an Outdoor large plastic box, they had 2 sizes, at Wally world and I drilled the side and ran wires through a drilled out cork and pressed the cork in hole I drilled in side of box. The box is sized just right. I hope this protects the battery connection, and I taped 2 extra connections to the inside of the box. For now I have run the wires under the cover, with a bit of extra wire there to let it move it has too, up front in my Revo13. It is mounted on a wedge mount on the sail mast support hole. It worked fine, even for me. LOL. I used duct seal to hold the transducer to hull bottom and I put a bit of water in it and it worked fine. Now I just need to catch fish.
I am real pleased with this so far.

I bought a cheap Eagle Cuda 300 for $69.  I only wanted it for the transducer because it was cheaper to buy the fishfinder on sale than to just buy a spare transducer($75) for my other fishfinder .  It has since become my primary fishfinder and seems bullet proof.  However, all it does is find the bottom and mark fish.  Nothing fancy, but that is all I need.

I settled on a Lowrance Mark 4.  It's a combo fish-finder and GPS chartplotter.  $187 shipped was the best I found.  From the research I've done it seems that the combo units are worth the extra price as it makes it really easy to mark waypoints when you see good structure, or other features you are after.  Plus the base maps include depth contours which you don't usually get in a normal handheld GPS.  It only just came in the mail yesterday, along with some waterproof 2-pin connectors I ordered seperatly.  I need to put everything together still before I can test it out.

I'm just getting started in kayak fishing as well, and recently the Lowrance mark 4. Im still learning the ins and out of the unit, but ive loved it so far! The contour maps built in the gps have made a huge difference since I don't know the water I'm fishing well yet. They include some but not all of the local lakes, but it has all of puget sound...

Gerald