I just went from a MK Terrova 80 I-pilot on my 1860 to a MK I-pilot 101 for the new Excel. I never noticed noise from the Terrova as an issue and I found a lot of the issues folks have with spot lock is of their own making by running up to a spot, push spot lock while the boat was still moving and then complain when it made the necessary corrections.. The 80 on my 1860 would let me troll in the roughest conditions I dared being in, would pull the boat at 4mph, and battery life was good. Never had any issues with the MK.

I will say the transducer inside the head on the Terrova is not as good as the transducer that comes with the HB units and it's strictly for 2D sonar. That's why I run one of rnvinc's "da'ducer apparatus" brackets.

da 'ducer apparatus - Podunk (po dungk) A small isolated town, region, or place that is regarded as unimportant. . . .