Tunaorlater,
Thank you for the link. I should have ask this question before but what is the vessel max speed?
As you know the R199 was a in-hull transducer. The thought behind these transducers was quite good i.e. don't have to cut a hole in the hull, no drag, etc.... But in reality the performance isn't good in 99% on the installations. The two main reasons is that you can't regain the round trip signal loss of shooting through the hull plus you are trying to shoot through the boundary/turbulence layer of water.
So what to do. If you are looking for Tuna in the upper part of the water column (<300ft) I would look at either the B-275 or R-109LHW. The LF side of the 109 will give you better deep water performance for fishing in canyons. However both transducers have speed restrictions of 30 knots.
Snips