I installed an Airmar b150m to use with a Lowrance HDS-9 head unit. This is a thru hull (as in drill a 2 inch hole) chirp transducer. The only thing I lost was down imaging. I would have to install the structurescan transducer to get the down imaging. I gained the ability to mark fish while running on plane, I never succeeded at adjusting the skimmer to work on plane. Now my boat will not go fast enough to lose bottom and I can clearly see fish at 15-23 mph.