My new depth sounder transducer for my Garmin will be delivered this week, I'm considering a "bath" type mount in the bilge. The transducer is 1.5" diameter, so I'm thinking a 2" chunk of PVC epoxied to the bilge floor, filled with pink RV antifreeze and capped.
Any downfalls or shortcomings regarding this setup?

I did the exact thing with a P-79 Transducer on a Garmin 546s. I get depth readings up to 50+ mph as long as the water is smooth, I am really pleased with the install.
My hull is cored so I cut a 4" hole in the inner layer of glass and sanded the inside of the hull smooth. I bought a piece of 4"od x 3" id PVC tube and used 3-M 5200 to
glue it down and caulk between the PVC and the inter hull. Make sure you place where you can clean water so so get good readings.

rrentsch, Getting ready to use the P79 with a new chart plotter, any pictures of your install and set up? Thanks, Robbie

I'm speculating here, but the PVC can be perpindicular to the waterline, and not canted, because the RV antifreeze is the medium, correct? I planned on mounting it near the bulkhead and low, about 4-6" up from the keel. I know the transducer auto adjusts up to 22*, but I have a 24* hull, so just smushing it into an epoxy bed would be close, but not correct. I prefer correct.

Robbie and Speedracer,
Sorry I didn,t take any pics. But I installed it in the same place PQ had the factory one installed. It was about 6" in front of the first step. I played around with a cardboard template to get the inside hull angle correct which was 28 deg. On the P-79 I had to cut the bottom angle of the PVC Tube 10 deg. less so the top was level. If you use 4"od x 3" id
the transducer will fit the id perfect. I put a small bevel on the id of the PVC and used the supplied o-ring to make it seal, then screwed the transducer right to the PVC. after the 5200 cured I filled the id with RV antifreeze and screwed the transducer down compressing the o-ring for the seal. It made a great intsall

I installed a P79 on my Raymarine last week. I followed the directions and tried various spots by temporarily taping it down on a Vaseline bed and it barely read anything. I finally installed it permanently in the anti-freeze and I was amazed how well it worked. The P79 I have rotates and has the deadrise scripted on the mount.

I was able to remove the factory transducer and filled the core hole with polyester resin to seal the core from moisture. I used the P79 as well with my 546s, it worked great the first weekend and then very sporadic since then. I use chart depth now. I'm thinking about switching to an external sensor, not pretty, but I need something that works.

I had to use a P72 and a 6/8 pin adapter with my 531s, but it works. Cut the pipe to match deadrise, epoxied it in (non-cored hull), cut a slot big enough for the wire, filled with RV antifreeze, capped with PVC pipe cap, dab of silicone around the wire exit. The cap is just press fit, and I've checked it a couple times over the last week with no loss of fluid in the pipe, so I'm satisfied.

Garmin doesn't recommend RV anti-freeze, they recommend automotive. I have found that RV antifreeze can jell up over time as well.

Noted... I'll be switching to orange Dex-Cool when I service the truck this fall.