Airmar depth and what is that?

[dstrout]

On my 1985 Baba 40 I have an old airmar depth sounder that goes through the hull. Next to it is ?something? that looks like a thru hull but doesn’t come out the other side (see pictures). Any clue what the corroded bronze thing is?

Thanks,
Dave

[capt jgw]

Looks like a through hull depth transducer that was glued inside the hull to make it a shoot through. That's not uncommon, I've done it a few times. Shoot throughs are often used to replace a through hull that has failed and they don't want to haul out to replace it. On closer look it appears the wire from the plastic one has been cut off, indicating the bronze one is the active unit. If you can get the bronze one unstuck without ruining it, you can remount it in the hole from the plastic one, but if they used epoxy that may not be successful. If the sounder is working, you're probably better off leaving them alone. If not working remove both and replace the through hull one, maybe the display too if you wish. This might be a good excuse to upgrade to a networked system.

[dstrout]

Lol - I kind of thought that might be the case but said “naw, can’t be”. Neither one works, and I’m in the process of putting in a B&G NMEA 2000 system.

Which leads to the second question- how the heck does the plastic one come out? From the inside it looks like you would unscrew the cap and pull it out. But it won’t budge. And from the outside it looks like it has a flange that makes it bigger than the hole. But I can’t believe it’s installed from the outside….

I have an airmar 810 combo depth / speed that I’d like to put there if I can get the old one out. Thru-hull is same threading, so it would be the easiest way of doing it.

Appreciate the help!

[capt jgw]

Yes it is installed from the outside. Unscrew the top cap, then unscrew the ring around the bottom. It will then come out from the outside. The sealant will probably be holding it in, you may need to drive it out with a block of wood and a hammer. If all else fails a hammer and chisel applied to the base of the flange on the outside should break the flange off and allow you to remove it from the inside. The hammer and chisel will take care of the bronze one too, from the inside.

[dstrout]

Fair enough- thanks for the advice!