transducer problems

[capthorace]

I have a garmin 4212 / 4208 (tower) and a transom mount ducer. Running I get noise on the screen and an unreliable bottom reading. Boat has new 8.1 Crusaders and Volvo out drives.

At a trolling speed I still get interference but the bottom locks on. Pull the engines out of gear and the noise goes away and I have a clear screen. I'm not so sure that the installer didn't splice the connector for the Garmin and used the old ducer.

I'm thinking about adding a in hull ducer this winter. Any suggestions on location and type? Plus any other info will be appreciated.

Thanks,
Horace

[OnTheHill]

I have the 3210, and it came with a magnet that attaches over the cable to help with interference. That may be all that it is. I would want to know before installing a new transducer. If it is interference, than a new 'ducer won't be the answer.