Forget it and go something colour.

cheers BME but like most things its more a $$$ issue.

To be honest I just use it in 200khz all the time.

Sorry my comment was a bit unqualified, I should elaborate.

Black and white sounders which now start at about $150, lower when they are on special are great for spotting channels and maybe some fish or structure, however since they generally only have 4 or 8 graduations of grey, there is only so much information which they can display.

A good colour sounder, such as this one:
http://www.paddleguy.com/trip-reports/first-kayak-fish-for-2013-brings-me-a-new-pb-snapper/
or a Lowrance Elite 4X starts at about $300 and they have literally hundreds of colours to differentiate, plus as has been previous mentioned, both the mentioned fish finders have a higher output power, 300W.

In real life these differences do make a noticable difference when searching for fish. I have been out on customers boats in the harbour, exchanging colour and black and white models and the ability to differentiate between a bit of turbulence, a bit of seaweed and a bit of fish is in my opinion worth the extra $150 or so.

In relation to the Furuno LS4100 and LS6100, although they would leave the other black and white models for dead, they are left behind by the colour models, and most people would spend the extra go for a FCV627. The result is that noone was buying them and they are no longer imported, even though they are officially a current model.

cheers guys gone the 4x pro and be delivered tommorrow, the old one worked well so its a upgrade and at the things are tight.but cheers for the help