Quote Originally Posted by grayryder View Post
i was wondering if i buy the helix 9 or 10 di unit can i buy a si transducer to add si or do you have to buy the si unit to start with
You'd have to have a SI "unit" ... it's not just the transducer that makes SI, the unit has to have the programming.

A Helix 9 SI GPS unit has SI, DI, 2d sonar, and mapping.
A Helix 9 DI GPS unit has DI, 2d Sonar, and mapping.

... cp