B and G depth transducer mechanical failure

[Kim Klaka]

2 years ago I fitted a B&G forward looking sonar. The transducer installs into a housing, with o-rings and a screw-down locking nut, similar to many speed logs. It also comes with a blank which you can fit instead of the transducer. Yesterday I was sailing in very rough seas with the blank installed, and it came out (i.e. it was pushed back into the boat) due to the water pressure when slamming in waves. How can this have happened? There is no obvious damage, and I am 99% certain I screwed the lock nut down. Having reinserted the blank there has been no further ingress of water for 24 hrs with the boat in the pen. Has anyone else experienced this? We ended up with 300 litres of water in the bilge before we discovered the source. I do not want it to happen again! Boat is being hauled out tomorrow so there is a good opportunity to inspect, but what should I be looking for?

[coopec43]

Well if it is anything like this blank then I don't know how it could be forced back into the boat. Is it the correct size. Alternatively is the hole in the boat the right size.

I think I'd be making up another out of a SS through hull fitting but blanked off.

[pjShap]

My Garmin transducer has an ear on the locknut with a hole for mousing wire, recommended to keep the locknut from possibly unscrewing.