Depthfinder Question

[CrownRoyal]

I ordered a Garmin 240 Fishfinder for the counsel of my new boat. The dealer installed a Garmin 240 "Blue". From what I understand, this is intended more for off-shore fishing. The 240 that I ordered has a 200 kHz transducer with a 20 degree cone. The 240 "Blue" that he installed has a dual frequency transducer, a 50 kHz with a 40 degree cone and a 200 kHz with a 10 degree cone. I do most of my fishing on the WI river (usually in less than 12 ft of water) with occaisonal trips to various northern WI lakes. The "Blue" version is about $75 more, but he would give it to me for the price of what I ordered.
My question is, do I even want this dual frequency transducer? I'm running a Garmin 240 (200 kHz, 20 degree cone) with universal sonar through my bow mounted Minn-Kota Auto Pilot. Would the dual frequency on the counsel be a good compliment to my bow mounted one?

I'm pretty confused over this. Any advice or comments would be much appreciated.

Thanks

[work2fish]

CrownRoyal,

From what you described about where you fish, you DON'T want the dual frequency setup. 200 kHz is better for the shallow waters. You must use a smaller cone angle for the 200 kHz on a dual frequency transducer and the 50 kHz is only good for very deep waters, anyway...

Regards,
work2fish