No.
When you mark a target with your 1198 using its stern GPS puck over the 1198 transducer, you are marking the target's location when the stern GPS is over it, i.e. Nxx xx.xxx, Wyy yy.yyy.
On the bow with the Terrova's GPS you navigate to Nxx xx.xxx Wyy yy.yyy and the bow is over the target.
Now if you idle to Nxx xx.xxx Wyy yy.yyy using the 1198 with stern GPS puck, then the stern is over the target.
Also you want the 1198 GPS puck close to the 1198 transducer because targets seen in the 1198 SI are measured from the 1198 transducer and GPS coordinates come from the GPS puck. Therefore the coordinates will be more accurate.