Depth
 

DonV,

How deep are you reading until your unit goes blank?
Running the b164 also, with the garmin 740s. Getting about 800. Was hoping to drop on some rosies :mad:

If you choose a "shoot through" transducer without temperature, what is the downside to not having that data other than determining "shrinkage" factor?

I have the Raymarine DSM300 module with my old clunker C120. I have trolled at 1400' and seen the contour of the bottom very well, that's as deep as I've had it. Can't say I would be able to pick out a swordfish or anything like that, never tried to zoom in to the bottom for rosies or the really deep guys.

Up to 30% loss signal loss on transmit and receive. Not a real problem in shallow water up to 150, but definately a problem in deeper water with units under 1000 watts. I once had it both ways on a Paramount superfish and ran a 200/50 glued inside. I did'nt know what I was missing until I transom mounted it. The biggest return issue when it was glued inside was the deminished fish show return.

Transducer mounting location
 

Still rigging my 23 CC and about ready to install a pair of Garmin GT51M-THP transducers. My concern is the best hull location. They seem really large for a 23' boat . I like the second step location but my concern is will this location effect the water flow to the prop with a single outboard mounted on a twin Hermco bracket?

If you mount outside the first step, the water will be aerated, no bueno.

Sell one and mount a single dead center of the keel. In all reality you could of gone with a transom mount and mounted it right next to the drain plug. That is where I mounted mine and it doesn't bother the motor whatsoever. Your bracket is much longer than mine so there would be no issue. I wanted to go thru hull as well but I didn't want to cut the center stringer but that would be the best place and I will make accommodations on my next build.

If you go with both thru hulls you will likely have to go with fairing blocks to get them low enough in the water.

The transducers come with fairing blocks that can be cut to the angle of the dead rise. I would be concerned with the first step mount in that it may cause cavitation. Shine said outside the first step becomes aerated. I also have reservations about cutting the center stringer. I may be forced to go with a transom mount if I can't figure out how to make these work. Thought it would be nice to have down view, side view, and chirp in one set of thru hull mounted transducers. Thanks for your input.

You still have all of those with a single transom mount and with your bracket it will have a clear view to both sides.

Moose. Do you think you could have mounted your Gt51 half way up the last panel?