Material between outer hull and inner shell

[Foobar]

Ok, so I started cutting holes today for an in hull transducer. (epoxy to the inner hull. no holes.) In the engine compartment many Yamahas have a cutout for the bilge pump. So, there is a clear spot under the starboard engine. I cut a hole into what I am going to call the inner hull. (I know, technically not.) The piece would not come out. I cut a small piece from the square so I could pry it out.

I found this very dense gray material between the two hulls, which stopped short of where they put the bilge pump sits. My thinking is that the transducer should be able to shoot through this material as it seems very dense. So, I patched the cuts back up with Marine Tex. Tomorrow I will sand and finish it. (8 hours wasted between cuts and repairing)

Does anyone have experience with using a transducer on top of this material? If I don't have to remove a square of it, I would prefer that. Removing a 4x4 square of it would involve a lot of knuckle busting.

 

[M@__]

I’d say consider a small hole above the waterline within the recess for the pumps. It won’t be seen and it wouldn’t pose a leak risk unless heavily loaded. Seal it up good and then you have a much better signal from the transducer.

Can’t say about that material, but waves refract or reflect at every material boundary. You’ll have four materials before even hitting the water...

 

[Van T]

My transducer is glued to the inside of my hall and seems to work not sure if it's less accurate guess you'd have to do a side-by-side comparison not sure if I had the same material in between my hall or if it's just the bottom layer of glass where I mounted it . If the material is super dense it's probably bonding resin.

 

[haknslash]

Why not just use the same area that people have already had success with using a shoot-thru transducer? Having it in the actual bilge (under the swim platform/cleanout plugs) is going to allow you to mount it closest to the water for better accuracy. I would not use the engine compartment area.

 

[Beachbummer]

Even though these transducers are solid state, in my experience they don't last a lifetime. After the second one failed I installed the next one outside like it's meant to.

Not sure why they failed on me, but they did. It's a possibility.

 

[Ronnie]

@Foobar if you haven’t already glued back in the material you cut out don’t. That is, I would test the transducer in that spot using a bag of water on the other side of the hull. I’ve installed a few in hull transducers now and recall that the instructions for doing this came with the transducer. It sounds like the material you hit is either adhesive or sound deadending material. I would have cut out what I need for the transducer if it didn’t pass the test with the water bag on the other side of the hull.

By the way I installed my though hull transducer opposite the stock transducer in my 242 Ls. It’s accurate enough (between it and stock I always trust the stock read out more) but installing in hull prevents you from getting external water temperature and speed readings if your depth finder / plotter has such features (mine does so now I know what temperature the water in the bilge is at, it is the temp I share with guests reluctant to get in the water). For speed I may have to install I different sensor outside the hull which I have not done because the stock is gps assisted, so very accurate and moreover I didn’t want to drill anymore holes in the hull unless under absolutely necessary.