Transducers & Fish Finders

[Johnatkatys]

I'd like to use my 2017 RT25-SC (Volvo Penta D3) for fishing. So, I started down the road of selecting a fish finder.
Okay, there are a lot of good ones, but I keep running into the problem of mounting a transducer somewhere. Seems like transom is the easiest.
So, question 1 might be: Do transom mounted transducers work? Will they get mucked up by propwash? Can you flip them up and out of the way when you go fast? Do they then interfere with the swim platform?
Has anyone done this? Got any real world advice?
Thanks in advance.

 

[gswearin]

Your probably get too much interference from the prop for a transom mount, but perhaps others have actually tried it. If you put it to the side opposite of the prop spin that's likely the calmest water. Ranger Tugs come with in-hull transducers and mine works pretty well. You could also do a through-hull for best performance, but you'd need to put a hole in your boat.

 

[Johnatkatys]

Your probably get too much interference from the prop for a transom mount, but perhaps others have actually tried it. If you put it to the side opposite of the prop spin that's likely the calmest water. Ranger Tugs come with in-hull transducers and mine works pretty well. You could also do a through-hull for best performance, but you'd need to put a hole in your boat.

The in-hull models seemed like a good choice, but according to some can only penetrate 5/8" reliably. The RT is a pretty stout boat and I figured it could be an inch thick. Do you know how thick the fiberglass is?

 

[Johnatkatys]

Your probably get too much interference from the prop for a transom mount, but perhaps others have actually tried it. If you put it to the side opposite of the prop spin that's likely the calmest water. Ranger Tugs come with in-hull transducers and mine works pretty well. You could also do a through-hull for best performance, but you'd need to put a hole in your boat.

My RT came with a in-hull Airmar P79 (depth only) transducer. It has occurred to me that upgrading it to a P79S (Smart) might work, since it mounts in the same hole and I have a built-in Garmin 7610 Chart Plotter which can operate as a fish finder. Not sure if it supports ClearVu or CHIRP. Still exploring that option.

Update: The P79S allows connection via NMEA2000, otherwise it's a P79.

 

[mikey]

I installed a transom mounted transducer on our C28 and it works great with a Lorance plotter/sounder. The top of the transducer is the same depth as the hull bottom so no problem at any speed. Had to drill a 3/4" hole higher up in the transom for the plotter plug in - filled with sikaflex and a SS clamshell then needed an extension wire to reach the plotter.

 

[Johnatkatys]

I installed a transom mounted transducer on our C28 and it works great with a Lorance plotter/sounder. The top of the transducer is the same depth as the hull bottom so no problem at any speed. Had to drill a 3/4" hole higher up in the transom for the plotter plug in - filled with sikaflex and a SS clamshell then needed an extension wire to reach the plotter.

Is the C28 an inboard?

 

[jeffhowell1]

I have a R-27 with inboard diesel. Not an expert but through my research found that transom mounted transducers don't work well on inboards, because of prop wash, as mentioned in original post. I finally gave up on P79 transducer a year ago, it kept losing reading and I could not access it. I had thru-hull transducer (Airmar B619 w/Garmin 8-pin connector) installed, port side next to diesel engine, opposite of water intake. Works fantastic, reads down to 1000', never loses bottom reading, also tells water temp. I don't fish off boat, so I wasn't interested, but there is panoptix now, or chirp clearvu for more clarity and more money.