Depth sounder replacement on C30

Nov 23, 2025
6
Catalina 30 Rock Hall
Hi all! I am sure this was discussed somewhere but am unable to find the thread. We need to replace the depth sounder on Catalina 30. We want the new one to fit in the old cut out, if possible. It is round with 4@ diameter. Anyone found any matches? The modern instrument all seem to be with square/rectangular or smaller in diameter than our current instrument (by Signet Scientific).
 

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
23,770
CAL 35 Cruiser #21 moored EVERETT WA
Welcome to the SBO Forums.
Is this what you are searching for?
1763930211251.png



If so they are found at SL172 Depth Sounder

Listed at $619, they are not cheap. A lot of alternate ideas are being used by sailors to identify and report their the depth.
 
Nov 23, 2025
6
Catalina 30 Rock Hall
Yes! This looks exactly like ours. Is this worth the price? Or if we are spending this much, should we go with the more commonly available Garmin or Raymarine? If we go with the instrument that is different in size/shake, what to do with existing cutouts? And could you please elaborate on the alternate ideas we should consider?
 
May 1, 2011
5,258
Pearson 37 Lusby MD
A lot of alternate ideas are being used by sailors to identify and report their the depth.
One alternate is handheld chart plotter, but it doesn't give you read-out in real time like a dedicated depth sounder. Another alternate is lead-line.
 

RussC

.
Sep 11, 2015
1,680
Merit 22- Oregon lakes
easy enough to make an adaptor ring for whatever size hole your new unit requires if you're unable to do the fiberglass work.
 

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
23,770
CAL 35 Cruiser #21 moored EVERETT WA
What other electronics do you have on board? What other displays are in your eyesight when you look at the Depth gauge?

When are you looking at - using - the depth gage? Are there other ways, like examing the chart and plotting your entry into an anchorage without a depth gauge? Do you anchor in the usual sites or are you always exploring unique and unproven anchorages?

If you did not have to install another round guage in the hole, what would like to have instead?

I know more questions than just replacing what someone else had. That is the fun of having your boat and making it yours. I am putting speakers in the holes that were used for outdated electronic gauges that do not work on my boat.
 
Last edited:
Apr 5, 2009
3,211
Catalina '88 C30 tr/bs Oak Harbor, WA
I had that same depth gauge on my C30 but went a different direction. I replaced it with a Garmin GMI-20 repeater. It can display most of my chart data or wind info.

I installed a Garmin chart plotter which also has depth on it. The Clear-vu transducer is mounted inside the boat on centerline just forward of the keel in the compartment under the vee-berth. It is mounted in a "water-box" that I made from a water-tight" electrical box and some plastic sheathing. I glassed this to the hull and filled it with Propylene Glycol antifreeze.
transducer chest.jpg

depth.png
 
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Nov 23, 2025
6
Catalina 30 Rock Hall
We are going to sail on the Chesapeake Bay which has rapidly changing depth and is often shallow so depth finder is important. Thank you for your advice against buying another Signet!! We really didn't want to deal with adjusting cut outs :( but i guess we don’t have much choice here. Thanks, everyone!
 

RussC

.
Sep 11, 2015
1,680
Merit 22- Oregon lakes
I just removed a Raymarine ST-40 depth instrument from my boat. keeping the transducer in place but I'd sell the unit cheep. it was working fine. pm me if interested.

unnamed-19.jpg
 
Feb 2, 2014
34
Catalina 30 mkII Pasadena, MD
I have an 87 Catalina 30 whose signet instruments gave up the ghost. For the panel instruments I cut a mounting plate to cover the old hole and mounted the new displays (except the wind instrument which I haven't mounted on the mast yet). As a test I used some scrap 1/4" plywood painted with outdoor latex paint, so I could see if I like the look or not. I now have three new mounting plates ready to install made of 1/4" HDPE Plastic Sheet, Starboard would also be a good choice. These pictures are from 2019, I really need to replace the wind instrument.

20191208_155444.jpg
20191208_155710.jpg
 
Nov 23, 2025
6
Catalina 30 Rock Hall
I have an 87 Catalina 30 whose signet instruments gave up the ghost. For the panel instruments I cut a mounting plate to cover the old hole and mounted the new displays (except the wind instrument which I haven't mounted on the mast yet). As a test I used some scrap 1/4" plywood painted with outdoor latex paint, so I could see if I like the look or not. I now have three new mounting plates ready to install made of 1/4" HDPE Plastic Sheet, Starboard would also be a good choice. These pictures are from 2019, I really need to replace the wind instrument.

View attachment 235619View attachment 235620
This looks very nice!
What Raymarine model did you replace Signet instruments with?
Did you have to replace transducer as well?
 
Jun 25, 2004
522
Hunter 306 Pasadena MD
This looks very nice!
What Raymarine model did you replace Signet instruments with?
Did you have to replace transducer as well?
There are companies that will cut the starboard to your specs, bevel the edges, and round the corners, all for not much money. I did this when I replaced my chart plotter, to make it fit in the existing navpod:
plotter.jpeg
 
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Feb 2, 2014
34
Catalina 30 mkII Pasadena, MD
I have the Raymarine i50 depth and i50 speed instruments (and the i60 wind instrument, not mounted yet). The depth sensor has to be replaced, but it wasn't too bad to do as I recall. I replaced both the depth and speed sensors, one was easy and the other turned out to be just as easy once I decided to drill it out from under the hull. You will need a hole saw drill bit, a drill and some sealant. Maybe a hammer to pound out the sensor, I used it on one the sensors. If the old sensor is in a bad spot you can add this one in a better spot and leave the old one alone, but then the old one becomes one more thing to worry about. I have my sensors installed in front of the keel and behind the front water tank cutoff valve.

My boat is just across the bay from Rock Hall, so I know how important a depth instrument is for the bay. The only time I "plowed mud" in the bay was when I was going into Rock Hall Harbor.
 

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
23,770
CAL 35 Cruiser #21 moored EVERETT WA
Mike.
Having a depth sensor is fine.

It will not keep you out of shallow water, nor from running aground. You need to know where shallow water is and know how to avoid it. If you choose to sail frequently, you are going to eventually run aground. The only sailors who never run aground are the ones that buy a boat in a marina and visit the boat on Saturday afternoon to share a drink with their dock mates.

I would encourage you to get a chart of the local area you plan to sail. Study the chart and stay in the waters that are deeper than your boats draft. When venturing out into the bay from your dock or mooring ball, there are likely channel markers. Staying within the channel is going to give you the best possibiity of not running aground.

Mother Nature is always challenging sailors. She lets sand bars drift and rocks appear. Your best defence is to get to know the waters. If there is a stream flowing expect there to be silt build up following heavy rain or rainy seasons. If in doubt, get in your dinghy and inspect the area noting the shallows so that you can avoid them.

Good luck and safe sailing.
 
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Feb 2, 2014
34
Catalina 30 mkII Pasadena, MD
Thanks for the advice. I have been sailing the bay for 13 seasons now and have touch bottom once and I was between the markers. I know the waters well around my marina and the surrounding areas. When we go to new areas like Rock Hall, Saint Michaels, Annapolis, Solomons, etc. we always update the charts and draw a detailed route sticking to a minimum depth of 20'. Of course the 20' minimum depth doesn't work when heading in, so we try to stick to a depth of 10'. Regardless, I still would not want to go without a depth instrument, it has saved us from going into uncharted and shifted shoals a number of times (mostly while heading into a marina or fuel dock). After one storm we even had a shoal form at the exit of our fairway in our marina (luckily is was still 8' deep so we were not trapped in the marina). I have a 5' 3" draft and I have the depth alarm set for 10', when it goes off I immediately turn towards deeper water, it works in the Chesapeake bay, but maybe not where you are.
 
Nov 23, 2025
6
Catalina 30 Rock Hall
I would encourage you to get a chart of the local area you plan to sail. Study the chart and stay in the waters that are deeper than your boats draft. When venturing out into the bay from your dock or mooring ball, there are likely channel markers. Staying within the channel is going to give you the best possibiity of not running aground.
Silly question but.. where do you get the charts? West Marine?