Leaky In-Hull Depth Sounder

[terpstra]

We recently bought a boat and have been fixing it up. One of the (many) issues is that the depth sounder does not work. We've root caused the issue to lack of fluid in the cylinder which holds the transducer against the inside of the hull. Unfortunately, after refilling the cylinder, we discovered WHY the cylinder was empty: it leaks the propylene glycol into the bilge rather quickly. Unfortunately, the mount that holds the transducer to the top of the cylinder is also seized, so I cannot easily remove it.

The obvious fixes that spring to my mind are:
- cut the cylinder off the hull and re-glue it elsewhere
- use sufficient force to free the transducer mount from the cylinder, dry it out, and reseal it with epoxy from the inside
- buy a new transducer and leave the old mount alone

My main fear with both cutting cylinder off and forcing the seized cylinder open is that I might damage the hull in removing the cylinder. Does anyone have tips?

[smac999]

if it's a p79 it should be attached with silicone or sikoflex. take a knife blade along the hull and it should come right off.

also the transduer just twists off.

how did you add fluid if the transducer doesn't come off?

[terpstra]

Thanks for the reply.

It is not a p79, unfortunately. I don't know what the model is. It just says "AIRMAR" on top with no other information I can access without opening it up.

It consists of three components with two threads connecting them. I've attached two photos:



The top-most component with the threading is the transducer. By adjusting the ring between the middle piece and the transducer, you can adjust the depth of the transducer within the cylinder. We got more fluid in by lowering the transducer so far that it fell into the cylinder and we could then add fluid around the sides. You cannot remove the transducer by adjust the top ring; the transducer does not fit out the hole on the top.

The middle and bottom plastic pieces are screwed together. If I could unscrew this part, it would be possible to remove and inspect the transducer properly. I could also then add glue from the inside.

There appear to have been two different applications of glue. The yellow/orange glue and some while glue on top of it. My guess is that a previous owner put the white glue on top to also try to fix the leak.

[capn ken]

The best fix unfortunately is not the easiest fix. Take it out and put in a new one.

[Jammer]

Looks to me like a homemade setup out of the ABS drain pipe section at the big box home center. That's fine if it works but since it doesn't you might as well replace it.


My first piece of advice would be to remove it from the hull and evaluate what's inside. I would be prepared to start over but depending on what you find you may be able to salvage some useful parts.