I recently installed a Garmin EchoMap CHIRP 42dv on my Oasis and am providing details for those who may be interested. This unit combines the features of both a chartplotter and sonar (fishfinder).
1. Battery Mounting: I mounted a sealed lead acid battery in the round hatch in front of the forward seating position using Hobie's battery mount.
2. Transducer Mounting: I mounted the Garmin GT-20TM transducer just aft of the round hatch in front of the forward seating position using the Garmin In-hull Transducer Mount. I also wedged a foam block on top of the transducer and mount to make sure the transducer stayed put even while on the trailer. This mount attaches with sticky adhesive and requires no cutting or permanent changes to the hull other than lightly sanding the area for better adhesion. Some water is required inside the mount between the transducer and hull. This water is temporary and I just add it before each outing.
3. Wiring - I ran the transducer and power cables out a single sealed hole inside the forward surface of the rear seat right mesh pocket. This pocket serves to hold the cables and ends when everything is detached. (Same for my Evolve control cable.)
4. EchoMap mounting: I installed the 8 inch H-rail on the right side of the aft seating position and mounted both the EchoMap bracket and the Evolve control using H-rail flat mount adapters.
This EchoMap model works very well and is the perfect size for a kayak. I find myself most commonly using a combination display with chartplotter on top and sonar on bottom as seen in the image above. The Garmin in-hull transducer mount is just a cheap foam cutout with adhesive but so far it has performed flawlessly.
Peter