What is this thing in the hull of my boat?

[Golden Time]

The previous owner of my boat had a car stereo mounted on the dashboard. There appeared to be an aerial attached to the back of the stereo but given that there were no speakers and it was all a hotch potch I took it out.

Following the "aerial" wire to find the aerial (as there is no aerial on the outside of the boat) it goes down into the storage space under the deck (hold?). Then it goes down into the little dipped bit of the hull to a circular thing that seems to be surrounded by masses of sealant/expanding foam. The wire is a solid core, plastic and then shielded like you would expect an aerial wire to be.

What is this thing? I cant imagine that is an AM/FM aerial built into the GRP Hull, surely AM/FM signal cant pass through a body of water.

I have attached a couple of pictures.

The Boat has a Garmin fish/depth finder fitted and the transducer for that is mounted at the back off to the side of the transom so I know its nothing to do with that.

 

[prv]

My guess is that it's a defunct depth transducer. Just because someone has installed the new Garmin doesn't mean they necessarily removed all the old stuff.

Probably the wire from it ran up to the dash to connect to the display, and was left behind when the display was removed. Then someone else fitted the stereo, found a coax cable floating around, and being used to cars rather than boats assumed it was an aerial cable. I guess they mostly played CDs (or cassettes?) on the stereo, the radio reception can't have been very good

Pete

 

[neale]

My guess is that it's a depth transducer.

Pete

Looks like a depth transducer.

Can I ask a couple of questions?

What diameter is the round bit bonded to the hull?

What is on the other side of the hull, is it in the bottom of the boat so it will be water, or is it somewhere else?

 

[Golden Time]

Looks like a depth transducer.

Can I ask a couple of questions?

What diameter is the round bit bonded to the hull?

What is on the other side of the hull, is it in the bottom of the boat so it will be water, or is it somewhere else?

The round bit is about 2-3 inches I would say.

Its in the very bottom of the boat, on the centre line of the width and almost central along the length of the boat.

Ive never had the boat out the water so I dont know whats on the other side yet. Boat is being lifted for windows to be replaced in a couple of months so I can look then.

 

[neale]

I would say then that it is almost certainly an old transducer. May well be nothing on the outside of the hull as it looks like it might be a 'shoot through the hull' type.

Agree about the likely scenario mentioned earlier that resulted in the stereo being connected to the transducer. Sounds very feasible.

 

[Golden Time]

My guess is that it's a defunct depth transducer. Just because someone has installed the new Garmin doesn't mean they necessarily removed all the old stuff.

Probably the wire from it ran up to the dash to connect to the display, and was left behind when the display was removed. Then someone else fitted the stereo, found a coax cable floating around, and being used to cars rather than boats assumed it was an aerial cable. I guess they mostly played CDs (or cassettes?) on the stereo, the radio reception can't have been very good

Pete

I would say then that it is almost certainly an old transducer. May well be nothing on the outside of the hull as it looks like it might be a 'shoot through the hull' type.

Agree about the likely scenario mentioned earlier that resulted in the stereo being connected to the transducer. Sounds very feasible.

Thanks guys, think I will trim the wire off close and forget about it. Just trying to remove all the **** in the bottom of the boat and sort out the crazy wiring that the previous chap had done. Including wiring everything that was inline fused INTO the fuseboard and everything that wasnt fused straight to the battery master switch. D'oh!

 

[PaulGooch]

Thanks guys, think I will trim the wire off close and forget about it. Just trying to remove all the **** in the bottom of the boat and sort out the crazy wiring that the previous chap had done. Including wiring everything that was inline fused INTO the fuseboard and everything that wasnt fused straight to the battery master switch. D'oh!

A tip for your fusing and switches. Throw away all of those inline fuses and wire everything up to a neat blade fuse panel. All of your fuses will be in one place and all the same style.

Don't wire things that have their own switches to more switches. Things like the fishfinder, VHF, plotter etc. Just wire them to the fuse panel and at the end of the day, turn the master isolator switch off.

 

[Golden Time]

A tip for your fusing and switches. Throw away all of those inline fuses and wire everything up to a neat blade fuse panel. All of your fuses will be in one place and all the same style.

Don't wire things that have their own switches to more switches. Things like the fishfinder, VHF, plotter etc. Just wire them to the fuse panel and at the end of the day, turn the master isolator switch off.

Exactly what I planned to do

The boat has a couple of 12v cigarette sockets that I am rewiring because they have been wired with speaker wire - should I put them through an Aux fuse switch or not bother because every 12v plug has its own fuse?

 

[PaulGooch]

Exactly what I planned to do

The boat has a couple of 12v cigarette sockets that I am rewiring because they have been wired with speaker wire - should I put them through an Aux fuse switch or not bother because every 12v plug has its own fuse?

I'd wire them to 20a blade fuses, no switches. The 20a fuse will protect the wiring, individual plug fuses can then be variably rated to suit the items being plugged in.

 

[sarabande]

in case the transducer is OK and a good brand, then it might be worth leaving the cable uncut ? One is not supposed to cut and rejoin transducer cable, IIRC.

 

[prv]

The boat has a couple of 12v cigarette sockets that I am rewiring because they have been wired with speaker wire - should I put them through an Aux fuse switch or not bother because every 12v plug has its own fuse?

If you don't have a fuse, and something makes a short circuit at the socket, then the wires from battery to socket will heat up, melt, possibly spark and catch fire. A fuse in something that may or may not be plugged into the socket will not help with that.

Pete