The 2d piezo in the Dual Beam xducer is the same as the 2d piezo in the MEGA xducer ...
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Haven't seen many tunnel hulls come thru the forum and I've been here a long time :-0
A tunnel hull will be as challenging as a pontoon install in that the opposing float will most likely create a surface for the SI beam to reflect off of and create an hard "close" return on that side of the SI image ...
Adding a mounting board to get the MEGA xducer even farther rearward may help - may not ...
You may be best served with a dual MEGA xducer install with the MSILR Y cable ...
https://www.humminbird.com/productDetail-Accessory.aspx?Pageid=728&id=12714High speed depth readings (from a transom mount xducer) will depend on how water flows out from under boat directly in front of the xducer ...
Is this tunnel hull aluminum or fiberglass...?? (There are options for both) ...
Rickie