I recently bought a fishfinder and was wondering what the different lines and thickness of lines mean.  I know it is showing the contour of the lake but why are there different thickness also it seems to show another type underneath the main contour what does that mean.

Thanks,

Jenga

Lots of depthfinders all have different ways of displaying the bottom, so I would just idle over some shallow water where you know what the bottom is so that you know what that type of bottom looks like. And the line under the main contour is usually just bedrock or mud

jenga,

  thats the same advice I tell all guys wanting to learn how to decipher what they see.

First off, you got to come out of auto mode to really see a difference.

I like to find swim beachs at lakes, its a harder sandy bottom,  I also like to find the soft mud bottom.    

Go over those a few times playing in auto and then manual mode playing with sensitivity.    Find a dam made of rocks that are steep, graph that, make some adjustments to get a better idea.

I like to go over large launch ramps.   You know the sides and such, if you are going slow or to fast as you go over, change speed of the graph to help with boat speed.    Some times chart speed is too slow, and you will notice you passed the edge of the ramp ten yards back yet just now showing on the graph.  

      Find vegitation, brush,    go to clear areas of the lake, find an old tree that is 2 ft under the surface, go over it.   look at the picture it gives.

Then move over a few feet, when does it not show on the screen at x amount of feet, it will give you an idea of the cone angle or how far in the deep of water it see on both sides of the boat.

ie........at ten feet, you may only see about 1 foot on either side of the boat.   Where at 20 ft, you see 8 ft out on both sides of the boat.    the deeper you go the more you'll see.

Matt

First you need to read the manual. It will explane the line width and what each one means.  Then go somewere you know what the botton look like and see what it looks like on the unit.

Have you guys seen the new Humminbird fish finders?  pretty amazing with the side-imaging feature? Pretty amazing.

Sure have Got a 997 si on the console and a 797 si on the trolling motor.