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Old 25-06-2016, 19:42   #1
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How to replace transducer without sinking

Hi CF Friends,

So, to complete our electronics upgrade project, the speed/temp transducer needs replacement. But, I don't want sea water rushing in through a 2-inch hole in our sloop.

Here's the question: Thinking about diving under and pushing a toilet plunger onto the bottom around the transducer opening to prevent water from rushing in when I remove and replace the transducer from inside the boat.

Have you ever done this? Will it work? Haul out isn't due under 2018 and this project needs done now.

Please share how you have solved this challenge.
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Old 25-06-2016, 19:48   #2
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Re: How to replace transducer without sinking

Many have a little flapper valve built into the thru hull which will stop most of the water. Even without, it only takes a moment to swap so really not much water comes in.
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Old 25-06-2016, 20:11   #3
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Re: How to replace transducer without sinking

You can swap it out while in the water without fear, well... mostly ;-) The first sight of the mini geyser is alarming, but in the time it takes to change it, you'll take on perhaps a gallon or three of water.
The adrenaline from it is actually a good reminder of why you always keep soft wooden plugs tied near each thru-hull. And to service the fittings, as well as your zincs regularly.
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Old 25-06-2016, 21:31   #4
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Re: How to replace transducer without sinking

i once took a safety course, and one of the things they suggested when taking on water is to drag a sail, or tarp, or sheet of plastic, under the hull (in a controlled manner, of course). a plunger wouldn't be easy to position exactly on the opening, but a larger sheet of water resistant smth is much less fidgety (and water pressure would guide it to the opening).

but i have never done this myself, full disclaimer.

anton
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Old 25-06-2016, 21:46   #5
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Re: How to replace transducer without sinking

Folks have used plungers to keep water out when doing throughhull work, but you can't just stick it on and then go back aboard and pull the transducer. As soon as you pop it out, air will go into the plunger and it will fall off; someone must hold it in place underwater.

Assuming that you have the blanking plug, it is a routine thing to remove the transducer and put the plug in its place. Have everything to hand, think it through before pulling, and y ou should not get more that a couple of litres in the bilge.

Jim
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Old 25-06-2016, 22:08   #6
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Re: How to replace transducer without sinking

Take the retaining nut off and push the transducer out with the tapered plug and then tap the plug in with a hammer so it stays in.


You can then go under and clean off around the plugged hole and when you are ready tap the plug loose and stick the transducer in the hole quickly.


I would fold the cable so it makes a flat coil about 12 to 18 inches long and tape it into a rod which will fit easily through the hole. I'd also have someone standing by inside to make sure the plug stays in until you actually want it out.


Should be a piece of cake.
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Old 25-06-2016, 22:49   #7
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How to replace transducer without sinking

Just swap it. I have some videos of us drilling a 2" hole in the bottom while the boat is in the water. No big deal. Just put the heel of your foot over the hole. Add a rag if you don't want splinters. People think there will be a gyser, but there isn't. A hand over the hole works too. Hydrostatic pressure is your friend. If you are 3 feet below the water, it's the same pressure that's at the bottom of a 3 foot piece of water filled pvc.

No big deal.

Btw, we put a thru hull in. Put an air filled balloon in the fitting. Worked fine. Just a balloon managed to stop the flow.



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Old 26-06-2016, 01:52   #8
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Re: How to replace transducer without sinking

My previous boat had a removable sensor but no blanking plate. There was a dummy transducer to swap in and out to fill the hole. I found that if I left the transducer installed, the paddle wheel would soon fill up with growth, and either stop working or become inaccurate. So I got into the habit of removing and replacing it every weekend I used the boat.

The first time was a bit daunting seeing the gush of water coming in, but in reality it was only a few litres. After that it was routine and no concern.

In your case, be prepared that your new transducer may not slip straight in and you may have to revert to the old one.
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Old 26-06-2016, 02:43   #9
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Re: How to replace transducer without sinking

Quote:
Originally Posted by UNCIVILIZED View Post
You can swap it out while in the water without fear, well... mostly ;-) The first sight of the mini geyser is alarming, but in the time it takes to change it, you'll take on perhaps a gallon or three of water.
The adrenaline from it is actually a good reminder of why you always keep soft wooden plugs tied near each thru-hull. And to service the fittings, as well as your zincs regularly.
Yeah this one.

It really is no big deal. Mine is about ten tonne steal mono. Very little water enters when taking out the transducer.

And to think that a few years ago I put a screw driver through my hull when I found a rust spot behind the gally cupboards and boy did I panic I was convinced I was going to sink. until I realised the amount of water was really very little.
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Old 26-06-2016, 04:09   #10
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Re: How to replace transducer without sinking

I've disassembled a gate valve on the water. Don't panic and work fast!
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Old 26-06-2016, 05:13   #11
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Re: How to replace transducer without sinking

What kind/type of sealant can be used if changing the sonar under water?
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Old 26-06-2016, 06:29   #12
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Re: How to replace transducer without sinking

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What kind/type of sealant can be used if changing the sonar under water?
None is needed. Normally its just a plug like transducer that fits inside the thru hull. Seal is made by an o-ring.
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Old 26-06-2016, 06:33   #13
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Re: How to replace transducer without sinking

I've done the plunger route to replace a thru hull valve. It works well and as mentioned you should have two people helping with one in the water.
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Old 26-06-2016, 08:48   #14
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Re: How to replace transducer without sinking

Reef magnet has it right... Work fast and have everything ready for the swap! I've done it several times and after the first experience, the drama drops dramatically. Cheers, Phil
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Old 26-06-2016, 09:39   #15
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Re: How to replace transducer without sinking

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Originally Posted by Caleb C View Post
Hi CF Friends,

So, to complete our electronics upgrade project, the speed/temp transducer needs replacement.
I am not sure if you're describing the removal and replacement of just the central part of the transducer (the "active" part with electronics) or the actual thru-hull. Here are some thoughts:

1. If you're thinking of replacing the entire through hull, that's a job for a haulout. It would take extenuating circumstances for me to try to do this with the boat in the water (like no boatyard within 1000 miles).

2. If you're talking about simply pulling the existing transducer and replacing it, this is really easy, and required if you want to keep the transducer clean. Unscrew the locking ring, pull the transducer, put your hand over the hole, and either keep your hand in place or put in a dummy plug. This is a very simple, safe, process. Yes, if you were to have a heart attack at the wrong moment your boat might sink, but it's not a challenging job.

3. Your new transducer may come with a sleeve that is installed in the existing 2" through hull which has a flap inside it. The transducer portion fits inside this sleeve, and it makes transducer replacement easy. Remove the transducer from the sleeve and only a little gurgle of water will enter the boat. I don't even put in the dummy plug for short term maintenance like cleaning the paddlewheel. I think most Airmar transducers are like this now. So, there's a through hull permanently in your hull, a sleeve with a flapper inside the through hull with a locking ring, and a transducer inside the sleeve.

Cheers,

Chuck Hawley

PS: I think the toilet plunger is an interesting idea. However, you'd start by creating suction on the area surrounding the through hull. Then by removing the transducer, you'd relieve the suction and I am not sure the plunger would stay in place.

cgh
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