Quote Originally Posted by Pastor View Post
Maybe someone on here can give me an answer before I plop down $800.00. I have a Helix 7 DI (without GPS) in front of boat with transducer mounted on trolling motor. I would like to replace the Helix 7 DI with a Helix 7 SI (with GPS). But I don't know if the SI will work with the transducer mounted on the trolling motor since the trolling motor is used to steer the boat. I know they take images of the bottom in different ways and have watched a couple of YouTube videos but have not seen an answer to my question. Any help will be appreciated. Thanks in advance.
As long as you're going in a straight line, you will get the same results as if the transducer was mounted on the transom. Turn the trolling motor in the slightest degree and your screen image will be skewed temporarily (just like your DI screen image does).

SI is basically an expanded DI ... the narrow fan shaped sonar signal just reaches out at a far greater angle/distance on the SI. That sonar signal is sent out at right angles to the forward facing transducer, so if the transducer is on the trolling motor ... you're signal direction depends on the direction of the trolling motor head.

As I understand it, SI images are best when you are moving at a couple of miles per hour ... but, I do know that many members do have SI units on their trolling motors, so it must work OK at slower speeds. I don't know, as I don't have an SI unit ... just a DI unit, with the transducer mounted on the trolling motor.