I have a Humminbird 898c SI on my BlackJack and had the transducer mounted centered, directly under my jackplate on the transom (external, not thru hull). The transducer is a little different than what comes with a normal sonar unit as this unit has Side Imaging capability. It will not work thru-hull and it has to be mounted externally. It had to be mounted so that nothing on the transom such as trim tabs, motor, jack plate, etc., could obstruct the Side Imaging sonar beam. The only downfall of my unit is that because of the way the transducer had to be mounted, it is only touching the water and giving me a sonar signal at slow speeds. Once I get on step, the transducer is slightly out of the water and will not give me depth readings until I slow down again. This is not a big deal for me because I fish Big Lake 99% of the time and I am very familiar with the waters. I usually don't use my sonar until I am moving very slowly anyway. If I was always fishing new areas I don't know that I would have gone with this setup. You shouldn't run across the issue that I have with a normal transducer though. I can't say anything about installing a thru hull transducer on the BlackJack since that's not what I have, but just by looking in the rear access ports it seems as if it won't be an easy task.
P.S.
(The black and tan one is mine!
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