I have an 898si combo with the transducer mounted at the rear of my boat and was thinking on adding a tolling motor transducer.  On the Humminbird website it give me the model number for the side imaging transducer but not one for 2D sonar only.  Is there a 2D only transducer for this model and is there any thing else I need to complete the job (switches,extra cables).  I did a search of the site but couldn't find the answer.  Thanks for the help.    
Turk