depth and speed sensor question

Batteries, Generators, Solar, Wind and Electronics

depth and speed sensor question

Postby Kommy000 » Wed Apr 10, 2019 3:09 pm

I found my speed sensor that is not installed and looks like there is a screw in plug where that sensor supposed to go in. I'm assuming it is possible to unscrew the cap and slide the sensor in and screw the cap back in while on the water? I'm guessing the water will go in so gotta do it quick. Also found my depth sensor but the setup looks different though both sensors go to 2 old screens from signet. I'm attaching 2 pictures, the red cap one is the speed sensor that just laying there and supposed to go into the thru hull with red cap.
And also, is that universal? Can I buy some new sensors so I can install new screens for those 2 new sensors or run wire to wireless router and make it all wireless on my tablet. Or do I have to get the boat out of the water and actually change the through hull for the new sensors. Again, the red ones look like simple drop in sensor and water tight cap but the depth sensor on other picture with black color I don't even know if it can be removed without removing the through hull.
Pic3.jpg (215.18 KiB) Viewed 2759 times
Pic2.jpg (150.14 KiB) Viewed 2759 times
Pic1.jpg (222.91 KiB) Viewed 2759 times
Posts: 17
Joined: Sun Aug 05, 2018 8:45 pm

Re: depth and speed sensor question

Postby bad » Thu Apr 11, 2019 10:26 am

Not sure what brand of instruments you have, but the technology is often similar, esp. for depth Sounders. See here ... ucer_ducer for some info it seems like you possibly can use the old trancducer.

Posts: 135
Joined: Sat Jul 09, 2011 11:14 am

Re: depth and speed sensor question

Postby Camino » Thu Apr 11, 2019 11:00 am

The red cap in the thru-hull is a blank. The red cap with the black cable leading from it on your floor is the speed paddle wheel transducer. Providing the threads are all good, and you have lubricate such as Marelon Lube, on the threads, theoretically you can quickly unscrew the blank and quickly insert and screw on the speed transducer. If there is no flapper valve in that through hull, when you remove the blank, a ton of water will enter( a few gallons at least I bet). The water will gush up a foot or two in height if the transducer is not immediately forced in and screwed hand tight.

The other transducer shown is your depth transducer. Do you show depth displayed on your instruments now? If not, either the depth transducer isn’t working or there’s an electrical problem somewhere. Quick edit - I see the depth cable coiled up next to the depth transducer so no you don’t show depth on your instruments. There is a reason both transducers show cut cables and blank inserted. The original instruments are probably shot I think but of course I can’t tell.

The sig marine or data marine through hulls and instruments are no longer made. I’m pretty sure that new parts would not fit into the through hull casing.
Tom and Stephanie
Good Way II F 35 (P)
1999. Wing Keel 5’
3GM30F, 3-blade maxi prop
Emery Cove, CA
User avatar
Posts: 205
Joined: Fri Oct 28, 2016 4:51 pm
Location: Stockton, CA

Re: depth and speed sensor question

Postby andygc » Fri Apr 12, 2019 7:50 am

If you can obtain the correct log impeller unit you should have no worries about inserting it afloat. I've removed a log impeller on many occasions to clear weed - that's why they are made removable afloat. The water pressure is trivial - a 2 or 3 foot head - which you can easily hold back with the flat of your hand while you put down whatever you took out and pick up whatever you are putting in. Log impellers normally have an O-ring, so as soon as the impeller is part way into the housing water flow will stop. The cap secures it in place and provides a secondary seal.

On a bad day I could let in a couple of pints of water, on a good day much less. In both the boats I've owned the housing has not had a flap - one isn't really necessary, and might be seen as just something else to go wrong.

But you are going to need a new depth transducer, and those are not made to remove afloat.
(UK Freedom 30 cat ketch, build number 107)
River Exe, Devon
Posts: 79
Joined: Sun Jul 31, 2016 4:33 pm

Re: depth and speed sensor question

Postby Lionel7 » Fri Apr 12, 2019 10:16 am

Signet marine is still in business in California. Last year I was able to get a refurbished depth instrument to replace my he original signet instrument. I could have bought a new one or refurb. I also had to replace the transducer as it was shot too. Ours is a lake boat so the instruments are less critical and I found replacing the originals to be easier and more cost effective than say going with new Raymarine or Garmin. The Signet guys were great and helped me through the installation and set up. The refurb instrument was a couple hundred bucks if I recall correctly.


Freedom 21
O’day 272
Posts: 18
Joined: Fri Dec 05, 2008 12:12 pm

Re: depth and speed sensor question

Postby mike cunningham » Fri Apr 12, 2019 2:42 pm

I have had mine out afloat a couple of times. Say what you will, looking down into the deep blue ocean thru the hole in my boat is unsettling even though I know I can stop the water with the flat of my hand. Haven't sunk the boat, so I must be doing something right.
Mike Cunningham
Freedom 30 (Mull) Hull #3
Build date...June, 1986 . Freedom Yachts USA, sloop, shoal keel
Gun Mount and pole retrofitted (purchased from a Hoyt Freedom 32)
Yanmar 2gm20F , 1600 hrs fixed two blade prop
e-rud and ocean racing equipment
User avatar
mike cunningham
Posts: 323
Joined: Sat Dec 20, 2008 11:21 am
Location: Jacqueline, F30 #3, Discovery Bay, California

Re: depth and speed sensor question

Postby BillSmith » Fri Apr 12, 2019 3:11 pm

This will seem common sense, but no one told me...

Comments in this thread speak to using the flat of your hand to seal the thru-hull. Yup. Do it in one motion. Don't sneak in from the side. Why?

What happens when you put your thumb over a garden hose. Jet stream! And that's what happens when you attempt to slide your hand over the gush of water. You get a rocket stream.

Had to clean our speed log often until our slips were dredged. Pull the plug or sending unit and QUICKLY cover with the flat of your hand in one motion as though you are trying to push the water directly back into the hole. That works for me.

Rinse with fresh water or your bilge smells. We get little critters that swim around in the shallow damp spots.
Bill & Carole Smith
Freedom 35 Pedrick
Coyote Point
San Mateo, CA
Posts: 63
Joined: Tue May 24, 2016 7:56 am
Location: San Mateo, CA

Re: depth and speed sensor question

Postby Camino » Fri Apr 12, 2019 9:03 pm

All the above is right. I mis spoke on sigmarine. I’m very used to pulling the speed paddle and cleaning and inserting the blank (lots of posts on this site to that topic). Please have a plug standing ready right next to you when and if you pull the blank- use either a purpose made wood plug that will fit that opening or a flexible soft plug that you can twist into the housing if something goes wrong. FWIW I’ve never used my hand over the opening in replacing or switching. I unscrew with one hand and have the other part ( blank or transducer) ready in the other and as I lift out one I “quickly” :D insert the other. Whatever technique is used it helps to practice :oops: Without a flapper valve lots of water has always come in- if one is not ready for that , one might panic, hence have a wood plug or similar at hand.

The real question I believe is do those existing instruments work and if not what to replace with. Raymarine or others have tack tic or whatever they are called and they can operate remotely but you still need to insert the transducer into the hole - depth and speed. Depth you will definitely need to be on the hard to replace.
Tom and Stephanie
Good Way II F 35 (P)
1999. Wing Keel 5’
3GM30F, 3-blade maxi prop
Emery Cove, CA
User avatar
Posts: 205
Joined: Fri Oct 28, 2016 4:51 pm
Location: Stockton, CA

Return to Electrical and Electronics

Who is online

Users browsing this forum: No registered users and 3 guests