I recently purchased a 1980 O'Day 23 with a non functional depth finder. I am looking to replace the depth finder and need to decide on a transducer for it. The boat has an ancient thru hull P-19 transducer that so far as I can tell is non functional or obsolete. My marina is willing to swap it out for the cost of labor (don't know how many hours?), but I am reluctant to reopen a hole in the bottom of the boat (the boat is currently amazingly water tight, rarely ever have to pump the bilge). So I am considering saving the cost of labor and installing an in hull transducer instead. Can folks tell me their experience with in hull transducers? Also, Garmin says that the P79 will work on a solid fiberglass hull up to 5/8ths inch thick. Can anyone tell me the thickness of the hull of a 1980 O'Day 23? I was planning to install it near the centerline in front of the keel. Thanks
In hull vs thru hull transducer?
- Thread starter Chart Guthrie
- Start date
I think you have these two types backwards. The in-hull is the one permanently placed in the hull while the thru-hull is mounted inside and shoots thru the hull. That being said, I replaced my in-hull after a lightning strike with a thru hull. Have not found a difference in either type. The thru-hull has to be mounted so there are no air gaps. I placed the puck in a zip lock bag, covered it with water, ( some use mineral oil) and wedged it under a settee near the center about where the in-hull one is. I did not remove that one. I don't have a recommendation for a specific brand but would imagine they're all about the same. The one advantage of the thru-hull is it can be moved unless you epoxy it in. I did not and have had no problems.
I did notice 2 holes in the tube on the bow of the boat and tells me it is there to use some kind of pin
that goes into the pole when stored or when extended.
that goes into the pole when stored or when extended.
Roland, actually the OP has it right. Any transducer, drain, or other feature that requires a hole in the bottom of the boat is referred to as a Through Hull (thru-hull). The transducers that mount on the inside of the hull are In Hull. The confusing part is that the term Shoot Through Hull and Through Hull are mutually exclusive, but some have interpreted that as synonymous. They are not. There's some good You Tube videos that discuss and show how to install both of these transducer styles.
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See reply #3 .......................
https://forums.sailboatowners.com/i...sounder-1980-h27.159064/&highlight=transducer
This is one project where the KISS principle is mandatory.
https://forums.sailboatowners.com/i...sounder-1980-h27.159064/&highlight=transducer
This is one project where the KISS principle is mandatory.
I used the standard transducer that came with my unit and never drilled holes in the hull. I mounted it as far forward as I could forward of the keel but not too far forward so that it will not miss read if the bow comes out of the water in big seas.
Before mounting the transducer you have to place the transducer into a ziplock bag full of water. Then place the transducer onto the hull untill it reads depth. You may have to move it around a little bit to find a section of fiberglass hull with out any air pockets or voids.
Only time I had found voids in a hull was in an old Ericsson. After good location is found mark the spot.
I cut the bottom of a deli salad container out that is larger then the base of the transducer this you will need to hold silicone later. Now place the deli container onto the hull and carefully fill the container with clear silicone avoiding making any air bubbles in the silicone.
Carefully squish the transducer into the silicone avoiding air bubbles. I angled mine slightly forward so that the unit reads the depth just slightly ahead of the boat. In theory this to give a little warning before you hit bottom.
I used this method for the past 40 plus years on eight boats and never ever drilled hole in hull.
Advantages of this are:
No holes, can be angled forward to read just before boat, and easily removed for serviceing.
Before mounting the transducer you have to place the transducer into a ziplock bag full of water. Then place the transducer onto the hull untill it reads depth. You may have to move it around a little bit to find a section of fiberglass hull with out any air pockets or voids.
Only time I had found voids in a hull was in an old Ericsson. After good location is found mark the spot.
I cut the bottom of a deli salad container out that is larger then the base of the transducer this you will need to hold silicone later. Now place the deli container onto the hull and carefully fill the container with clear silicone avoiding making any air bubbles in the silicone.
Carefully squish the transducer into the silicone avoiding air bubbles. I angled mine slightly forward so that the unit reads the depth just slightly ahead of the boat. In theory this to give a little warning before you hit bottom.
I used this method for the past 40 plus years on eight boats and never ever drilled hole in hull.
Advantages of this are:
No holes, can be angled forward to read just before boat, and easily removed for serviceing.
I mentioned in an earlier post that that was what I had done. However, I failed to mention that I also placed the bag with the puck in a short piece of PVC pipe to help keep it stable. Four years, or so now, and no problems. Just have to add a little water every few months. Never did epoxy it in.
The key word is "solid" fiberglass. A transducer cannot shoot through air so a cored fiberglass hull would be out. Sometimes even solid fiberglass has pockets of air so it may be necessary to try out different locations if at first you do not succeed. As far as location it really does not matter as long as it is not at a location which frequently comes out the water. Make sure the seal between the transducer and the interior surface of the hull is free of air.
Never heard of a useful and accurate forward reading depth meter. It is the depth straight down below the boat that I'm interested in. Here in Florida it is a game of inches and an accurate depth meter is an important tool. Our transducer sits near the keel and we have calibrated with a 6 inch offset below the keel. Calibration was done after a soft grounding of the keel to establish the actual draft. Now when we get a reading of Zero we know we only have a margin of six inches. Any reading below 2 feet triggers slowing the boat down and anything below a 1 foot merits moving at crawling speed. It is not fun when you happen to find perhaps the only rock in your way. The depth meter is also used to verify position in a chart especially when navigating in fog or low visibility. If the meter reads 6 ft and the chart indicates a depth of 25 ft at that position you are not where you think you are. It is of help when anchoring to help determine scope and swing room.
I sail in Barnegat bay Nj where like on others have posted sometimes I too only have inches under the keel. That is why I have mounted my transducer at a slight angle forward. This directs the signal just forward of the keel approximately just under the bow. This works really well when I am in very shallow water. It gives me a depth reading before grounding. All depth sounder are different regarding callabration settings, mine I was able to callabrate within 3 inches using a role up tape measure and a waight.
My P79 came with the surrounding fitting so no need to make a pipe fitting to hold it. I didn't use the fitting, just stuck the transducer in a wad of toilet ring wax. Stuck it in place to try out the location and its been there for over two years.
One caution on putting it on the centerline in front of the keel. The centerline, all the way up to the bow, is probably much thicker than 12"s to the side of the centerline. At least it looks it on my O'day 25.
Mine is about 18" to the side on the keel about mid way front and back.
Sailboats don't have good brakes so there really isn't much advantage to putting the transducer more forward than aft.
Heeling may throw the depth off a bit but if I am approaching water depth equal to my draft I am certainly depowering the sails so I am not heeled over and moving a bit slower.
One caution on putting it on the centerline in front of the keel. The centerline, all the way up to the bow, is probably much thicker than 12"s to the side of the centerline. At least it looks it on my O'day 25.
Mine is about 18" to the side on the keel about mid way front and back.
Sailboats don't have good brakes so there really isn't much advantage to putting the transducer more forward than aft.
Heeling may throw the depth off a bit but if I am approaching water depth equal to my draft I am certainly depowering the sails so I am not heeled over and moving a bit slower.
Our old Signet Depth Finder is forward shooting thereby giving you a warning if you are about to run aground in a shallow cove or whatever....Works well and it's also useful for anchoring at night when the boat swings the alarm will actually wake you up in advance of the boat reaching the set alarm depth....I've had the boat since June of 1986 and the depth finder is
still working very well....our boat dealer installed it forward of the keel and set the preset to allow for the location above the keel depth which is the boat's lowest point; approx. 4 inches below the bottom of the keel.....I'm getting ready to install a new
Garmin Echo MAP model 43 DV.....we'll see how this goes....using the salad bar packaging per above post. Any suggestion
please reply to me....Spring is coming on the plains....72 degrees right now....and thru the weekend until Tuesday......Patrick
still working very well....our boat dealer installed it forward of the keel and set the preset to allow for the location above the keel depth which is the boat's lowest point; approx. 4 inches below the bottom of the keel.....I'm getting ready to install a new
Garmin Echo MAP model 43 DV.....we'll see how this goes....using the salad bar packaging per above post. Any suggestion
please reply to me....Spring is coming on the plains....72 degrees right now....and thru the weekend until Tuesday......Patrick
I installed an in-hull HawkEye sounder in my Catalina 25. I bonded the transducer to the inside of the hull as close to the center line as possible (swing-keel version of the C 25). The instructions that came with the sounder were clear and straight-forward. The price (as I recall) was about $100 for everything. So far, I'm happy with the system.
I like my Hawkeye D10D too. Great price, works well.
Encased in a short PVC tube. Shoots through the hull in a bed of toilet wax.
Encased in a short PVC tube. Shoots through the hull in a bed of toilet wax.
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