Hello,
I recently installed the 898, I installed the y cable and shoot thru hull puck.  I also (maybe unfortunately) installed 5.7.  Why ?  because I thought it was the right thing to do since I was prompted to on the Humminbird website.  Playback symptoms:  very slow and pixilated playback. When I begin playback in SI I get a short recording that scrolls onto the screen about 1 inch then stops.  After about 5 minutes the image begins to scroll again and the image is actually ok but it seems to take about 10+ seconds for 1 second of recorded time to play.  When i try to fast forward it only speeds up slightly, almost a negligible difference. 
On another site I was told to install the original software version.....Problem is I do not know what version was on my unit to start with.  Can i load my prior version software? if so how do I find out what was on it?
I have some really cool stuff I want to watch prior to y next trip.
Thanks in advance for the assistance.