how hard to install is a humminbird 997?

If you posses adverage common sense, can do simple 12V electrical connections, and can use tools, it very easy.

The most unusual adaptation for sonar installations is the way the SI transducer has to function.

It has to be mounted on a boat's exterior and be positioned so it can "see" horizontally, unobstructed, to the left and right as well as downward.

If you need more specific help, you may e-mail me with your questions and concerns.

purdum43@aol.com

I'm about to go thru this myself.

I only have about 4" of unobstructed space at the transom (I don't have a jack plate). Is that enough space for the transducer to do it's job?

As long as the side of the transducer can be seen from the opposite side of the motor mount it will work OK. It is best to get it as low as possible to eliminate the possibility of getting close range echos from the other side of the motor mount.

The tranducer actually "sees" to the water surface, not just horizontally.

If your hull is stepped, put the bottom of the transducer even with the step.