I have a Hummingbird 525. The transducer is hooked up to a pontoon the right side toon where there is a little welded peice of mettal. My reading on the fishfinder alway,s reads 1 to 3 foot witch I know is deeper around 5 to 6 foot or more. The bottom alway,s shows flat with light brown bottom witch I know can't all be flat. Do you have any sugestions about that what could be the problem? Could it be interference with the aluminum.

You sure you have it pointing down?  Is it underwater?  Sounds like you're picking up the other pontoon.

http://www.humminbird.com/support/FAQ.aspx?faqid=56

Yes it level and yes its under water.How is it picking up other pontoon.Thanks for the link but they don't tell you much.

Many depth finders can't cope with very shallow water and tend to lock up.  When I'm in very shallow water my Lowrance units will give me insane information, e.g. 2000 feet.  The solution is to take the boat back into deeper water, say ten feet.  The unit will then correct itself.

Yes it level and yes its under water.How is it picking up other pontoon.Thanks for the link but they don't tell you much.

Like if it was twisted down, and pointing at the other pontoon.  The link was just to show you the hay it hooks up.  Sounds like you have that part straight.

Mike's advice sounds reasonable, though I've never had that happen with my HB 383c. My buddy has a 525 or 535, and I've never noticed it either.