Re: [Amel Yacht Owners] Sonic Speed


I have replaced the forward sonic sensor twice (long story and she has promised never to "help" to clean the hull again). The procedure was:

1) disconnect wires from B & G control box.
2) solder a 4 meter retrieval wire to the end of the sensor cable
3) remove the couch seat back from the forward bulkhead - it is velcroed on.
4) remove the heavy felt from the forward edge of the forward fridge / freezer - it is also velcroed on.

You now have exposed the wires from the speed sensor. You will need to cut the nylon cable ties in the B & G control unit locker (forward, bottom, starboard in main cabin on SM#331). The wiring then goes through the forward floor locker in the main cabin, next to the bilge shut off valve and you will need to cut nylon cable ties here also. You should be able to easily pull the wiring through to the fridge / freezer leading edge shelf. If not, you have missed a cable tie - so put your head back down inside the lockers.

5) With your vessel OUT of the water you will need a small drill and a self tapping screw. Drill a pilot hole into the old speed sensor and then insert the self tapper. With a pair of pliers it should slide out easily.
6) To re-install, the reverse procedure. Use silicone grease on the interior "O" ring of the sensor socket and a dab of glue (I used silicone sealant / glue) on the end with the rubber - just to seal it.
7) When the glue has dried, cut the rubber block flush with the hull using a very sharp razor blade.

No hull grinding required. I ordered the replacement sensors from Amel and they arrived from Ponchon. B & G said the sensors had not been manufactured for "a decade" (??!!!)

Don't worry about the sensor leaking; the tube it is installed inside has the upper end above the water line. Sorry I can't help on the rear sensor but I seem to remember that it looked easier.
DoodleBug SM#331

----- Original Message -----
From: Ian & Judy Jenkins
Sent: Tuesday, May 13, 2008 9:01 AM
Subject: [Amel Yacht Owners] Sonic Speed

Hi , me again. We have the B & G sonic speed on our SM. Worked perfectly for 30,000 miles but this season either worked perfectly or showed between 0.2 and 0.3 k. The log and Apparent/True wind speed followed suit. All three displays, one analog and two digital, worked in sync, so its not a display unit problem
The local B & G man here in Trini thinks we may have moisture in one of the sensors. He is going to test it to see ( there is some resistance measurement you can carry out but he needs to get the figures from B & G HQ).
If his diagnosis is correct he says that replacing the sensors is a difficult job, involving a certain amout of grinding back on the hull. If this is so, I will wait to have it done by Pochon in Guadeloupe.
My question is: Has anyone else suffered this fault or had to replace their Sonic Speed sensors and if so what was the procedure? I have also asked Olivier for his comments and will post them.
Fair winds, Ian and Judy, Pen Azen, SM 302, Crew's Inn ,Trinidad

All new Live Search at

Join to automatically receive all group messages.