Thanks for the help. Just to clarify, you are saying to call Hummingbird and not Motorguide? I know the trolling motor transducer has been replaced once already by the previous owner. I really appreciate the help sir.

Yes, call Humminbird. They can help you deal with RFI.

Your trolling motor is "broadcasting" on the same frequencies that the sonar unit is using. There are filtering, grounding, and blocking remedies that may work, You just have to go through the process of figuring what may work.
There may be no fix in your case other than replacing the motor or getting it rebuilt.

There is no one-size-fits-all remedy. Each installation is different.

Thank you very much.

LakeMaster or Navionics are your options. Try your local HB dealer or Shut Up N Fish sells them too.

Could the interference I was describing above be caused by a messed up prop? I noticed my trolling motor prop had a crack and a pretty good chunk out of one of the blades. Could this be causing the interference with my sonar? I bought a new prop today but haven't replaced it yet. Thanks.

It could if the Harmonic Noise from the Prop is the same frquency that the Unit is listen for.

Doug, I just watched your dv tricks just posted on youtube regarding waypoints and using tm to navigate to waypoint. Is the heading sensor only available for ipilot? I have two 1198s connected with ethernet, and lakemaster mapping, and MN fortrex tm. Is heading sensor an update on software from HB? Explain what heading sensor is compared to current boat icon software....does it stay positioned correctly even with boat not in motion? I currently have two separate GPS receivers...each one being AS-GR50. What would the newer receivers do for me with my current setup? What model should i use for my current setup....without i pilot?

New boat with new Hummingbird 998 at the console and 798 at the bow. 998 will not recognize the SI/DI rear transducer. Just black screen where it should be. 2D sonar is working fine. 998 will recognize the SI/DI transducer on the trolling motor. SI/DI transducer not listed in the available transducer list.

Ranger had the 798 GPS puck hooked in with a Y cable and had it plugged in wrong. Maybe they have the 998 transducer wrong??

I would have the boat back at the dealer and let them fix it.

That's probably what's going to happen. Waiting on a top for the boat and will get that addressed at the same time.

They connected the Y Cable Backwards. This video will help you understand the AS SI DB Y Cable better http://youtu.be/BCuCOPhyGZs

Doug,

I took the 998 out of the console on Wednesday and checked all the connections. I didn't find a Y cable. I unplugged the cables and plugged them all back in. Went to the lake on Thursday morning. Turned the 998 on and everything was working.
I guess they didn't have the cables plugged in good enough or something.
My dealer had already sent in a warranty request to Ranger and a new transducer is in route. I have a new 1198 on order and will be hooking it up at the console as well via Ethernet. Hopefully it will all continue working.

The AS GPS HS is an optional accessory or come with a 360 Imaging System. But you can add to your network to get Heading Sensor to help in Slow Speed Navigation. Here is link to the Receiver: http://store.humminbird.com/products/629922/AS_GPS_HS

Hey Doug. I installed the HS GPS receiver. Why is my boat icon pointing one direction and the direction arrow pointing in another direction? It looks pretty weird. Is there some kind of adjustment to correct?

Were you drifting? The Heading Line tells direction the boat is moving with the AS GPS HS (Heading Sensor) but the boat could be pointed a different direction. Like a side wind. If you are defiantly going the same direction as the boat is headed you need to set the Direction Offset for the Heading Sensor Compass. Forgot the exact menu it's under but you can adjust to match the heading sensor with the direction of the boat is pointed.