Transducer Removal

[irwin28]

I'm wanting to Install a new depth finder in my boat forward of the keel in this perfect spot where there are already 2 transducers mounted in my way and I was curious to know if there is a safe way to remove them without damaging the inside of the hull? If its possible I would LUUUUUV to know how to do this.

[Pete7]

Depends on what you currently have. Are they through hull like a paddle wheel and depth sounder or are they glassed or bonded to the inside of the hull. Also what make are the current transducers and what are you fitting in place.

I switched from Stowe to Raymarine which involved a bigger hole. After unscrewing the Stowe I rammed a wooden bung in to the hole from the inside. Next cut the bung flat with the outside of the hull then used a good quality hole cutter from the outside to cut a bigger hole and fixed the new transducer back in with sikaflex. About 30 minutes for the two transducers.

Pete

[irwin28]

Its a Raymarine that is currently connected to it but will have to look at the other to see what type it ys but both are epoxied to the hull fairly well.

[s/v Jedi]

Originally Posted by irwin28

Its a Raymarine that is currently connected to it but will have to look at the other to see what type it ys but both are epoxied to the hull fairly well.

I guess you mean they are attached to the inside of the hull and fire through the hull (no holes in the hull).

In that case you definitely need a Fein Multimaster. It'll allow you to shave them off the hull as simple as it sounds.

cheers,
Nick.

[irwin28]

Much appreciated, yes it is attached inside the hull "thru hull" and I never really thought about something like that, guess I will go look for one of those or something like it.

[Pete7]

Raymarine use Arimar transducers, what make are you going to replace it with?

There is just a chance that whilst the transducer is different, the Arimar base that is glued to the hull is the same.

Pete

[irwin28]

I don't have the model # of the old system with me but it is a very old model that hasn't worked properly since I purchased the boat about a year ago. I don't believe it has the same transducer but will love it if it does.

[s/v Jedi]

If the markings on the transducer state P-79 then you have a good chance of finding a transducer that fits the housing for any brand depth sounder or fishfinder. The housing has a screw-on lid in that case.

cheers,
Nick.

[irwin28]

Man that would be so awesome, I believe that there is a good chance for it if thats the case. Now the anxiety of getting to the boat and checking to see if it has one lol, How far back have they gone with that made that P79 model?

[s/v Jedi]

Originally Posted by irwin28

Man that would be so awesome, I believe that there is a good chance for it if thats the case. Now the anxiety of getting to the boat and checking to see if it has one lol, How far back have they gone with that made that P79 model?

Oh, a long time, I'd say 10 years minimum. I am not sure if the marking is also on the housing (tank) itself. The tank looks like this:

If you see that, there's a P79 inside. There's also mineral oil in it. If not, or too little, know that baby oil is perfumed mineral oil

cheers,
Nick.

[osirissail]

Originally Posted by irwin28

Much appreciated, yes it is attached inside the hull "thru hull" and I never really thought about something like that, guess I will go look for one of those or something like it.

Huh??? Epoxied to the inner face of the hull is not in any way shape or form "thru hull". "Thru hull" means a hole cut through the hull and the transducer is inserted into the hole with adhesive caulk and tightened down with a large nut or something to hold it in place.

[Pacey16]

Can anybody tell me if an in hull transducer will work through a 1"thick cedar hull with 3/16" fiberglass either side

[s/v Jedi]

Originally Posted by osirissail

Huh??? Epoxied to the inner face of the hull is not in any way shape or form "thru hull". "Thru hull" means a hole cut through the hull and the transducer is inserted into the hole with adhesive caulk and tightened down with a large nut or something to hold it in place.

The confusion is caused by many calling these as firing (ultrasound) through the hull as opposed to using a thru-hull fitting.

Originally Posted by Pacey16

Can anybody tell me if an in hull transducer will work through a 1"thick cedar hull with 3/16" fiberglass either side

It won't work, you need solid fiberglass. We are balsa cored but the area around the keel and other high-stress areas become solid fiberglass so you might still be able to find a spot for it. You can normally see where it changes to solid glass on the inside.

Our P79 600W can see 200' depth when the bottom gives a good reflection.

cheers,
Nick.

[Whimsy]

Originally Posted by Pacey16

Can anybody tell me if an in hull transducer will work through a 1"thick cedar hull with 3/16" fiberglass either side

What Jedi said. The sonar will not send and/or receive the signals through any porous material like wood or foam, or even air bubbles trapped in otherwise solid fiberglass.

You can, however, easily test an area of your hull for effective "shoot-through-hull" transducer function by doing a temporary install in a glob of grease-based modeling clay (Wal Mart toy dept, $2/#, packed in 1/4# stix kinda like butter).

I have to go, so I'll just paste a piece I wrote for my buddy and let you sort out the details pertinent to your application, if you like:
~~~~~~~~~~~~~~~~~~~~~~~~
The transducer can be bedded (in a glob of the old-style grease-based modeling clay) on the center of the inside of the hull, just fwd of the keel stub, accessed through the under vee berth storage hatches.

Clean the hull surface well with clear ammonia water (not cloudy with soap). Then heat the clay glob by kneading it with your hands for ten minutes, or roll it out thin and let it heat in the sun - maybe a better idea, as it wants to be plenty warm and soft.

Just before attaching the clay to the hull, dry the area well with a hair dryer as the hull maybe colder than the often humid air and could be slightly damp with condensation even if it seems dry. Smear/adhere a thin layer of clay onto the area for good base adhesion, then smear on thicker layers until a level base is formed.

One key to making this work is to not have ANY air bubbles in the clay or hull laminates - the transducer signal will be degraded or not work at all through air-bubbles (or a cored hull laminate - unlikely in your boat), but just fine through clay, solid fiberglass and water. Some people make a dam/mold and bed the transducer in epoxy paste, others epoxy a pvc cofferdam with a screw on lid and mount the 'ducer in a bath of mineral or silicone oil. Clay was suggested in a forum as a temporary solution to "try out the position". Then another guy said his has been good for years - why do more?

When bedding the 'ducer in the clay, make a slightly convex surface (to avoid trapping an air bubble), while the clay is still warm, and push and twist 'ducer down into the clay. It will only go in a little. Then smear more clay onto the sides to build up the bedding effect.

ETA: This has worked well for a couple smaller boats, and then on a temp install in our Morgan 41' to deliver it to our local marina. The GSD22 sounder unit shoots though the hull and on down to ~600', near as I can tell - works fine.

[Whimsy]

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