Networking Humminbird SI to DI units

I'm looking at upgrading my my front HB to another 900 series unit or similar so I can network with my 998 HD SI I have at the console. If I only get a DI unit for the bow, can it still read off of the SI transducer in the back or even receive data from the console unit? Is there a good read or post about what I can and can't do before I get into this too far? I realized today that I'm kind of lacking not having a GPS up front for me to be able to mark spots as they happen and to see the chart as I'm fishing along.

Yes, they will share waypoints,2d, GPS,si,di. They will not share mapping. If just want to network the two units together you will just need an Ethernet cable. Depending on the 2nd unit need an Ethernet cable adapter if you purchase a xx9 or helix. The 998 need one of the later updates in order to network. You will also be able to share the di with the si unit but that will require adjusting the network setups within the units itself which is not that big of a deal

The 9X8 series is limited on what it can "see" from other units. I have owned a 958 and a 998 and all they should see from the other unit was the 2d transducer. even with the latest updates. The 9X9 series can see technology from other units as can Helix.
My current set up is a Helix 10 SI at the bow, a 998SI at the console and a Helix 10 (just plain sonar) at the console. I only have power and a network cable plugged into the console Helix 10 and it can display SI and DI views from the other SI units.
If you get a Helix 9, 10, or 12 you will be able to use the 998's transducer. What can make it cumbersome is that if you want to use SI off the other unit you have to change the transducer you are connected to meaning you will lose your DI up front until you change back.
All units will share waypoints but not maps.
Two accessories can change your life up front: the remote control and the Heading sensor GPS. I almost consider the remote control to be a safety device. Bending over to change views or settings in waves can be an adventure, only time I almost fell out was doing this. The heading sensor really helps fishing off shore when trying to stay on a way point.

Rickmb, you mentioned I would lose DI up front if I wanted to use the other unit's SI until I changed it back meaning the transducer setting on the bow unit? I think I've narrowed down to a Helix 9 DI at the bow using my current DI TM transducer puck networked to the 998c SI at the console.
With this setup I should be able to use the SI transducer and "see" what the 998 is seeing or is it only going to display 2d and DI on the Helix since it is only a DI unit? I assume that I have to buy an additional Lakemaster and Navionics chip to have the exact same maps since they don't share maps?

No not the transducer selection, the sonar and advanced source in the Ethernet menu.

If you want to add mapping and have both units with the same maps, you need a map card in both units.
You do not have to have both of the same brand, you can have Lakemaster in one and Navionics in the other if you want. The GPS functions the same way with or without any background mapping. Mapping is just a background on the Plotter view.

Ok, scratch my previous plan. I am getting an 859ci HD DI from a buddy of mine when he gets back in town. That for sure will be on the bow and my current 998c HD SI for sure will be at the console. I already have a Navionics and Lakemaster card I will use for them. Navionics in one and Lakemaster in the other for the map and contour overlays. My current HD DI transducer I have with the 596c HD DI will be used with the 859. I just need to know what else is needed to make this work. Just an ethernet cable between the two?
For sure, as I understand, I won't be able to share transducers between the two because of the way the 998 SI 'ducer works but that's okay with me. All I'm 100% interested in is the waypoint sharing which is not a problem. If I choose to do a NMEA link, will it share weather if I happen to buy it for one or the other?

The 859ci HD DI Combo needs an Ethernet adapter to connect the Ethernet cable to the display AS EC QDE since it does not have the threaded Ethernet port that the 998c HD SI Combo has.

You will also need a software version at least 6.640 or higher with the 998 so it will "talk" to the 859. Since you have to go that high, install the current software version.

The 859 will display SI from the 998.

If you have the proper DI transducer for the trolling motor for that model DI unit you can also share 83/200 kHz sonar. XTM 9 WIDE DI 20 T. Change the Connected Transducer setting to DI 83/200 kHz.

Yes they will share GPS data, not only waypoints but a GPS antenna also. The waypoints will not be copied to the other unit. They will be displayed in another color.

Thanks for clarifying Wayne, that's what I meant. Your views will be based on what you select from your Sonar and Advanced Sonar tabs under Networking.

You can always go to the network setup tab in the menus and see if the options for SI are available on the unit up front. That will tell you what you can network.

IF you are looking at a second card you really need to look at the Navionics Updates card. The price is great and the ability to update and select specific areas make this card awesome option. http://www.navionics.com/en/navionics-updates. They also have a bundle offer that is through June when your purchase a new qualifying graph.