ST50 speed sensor

[John Langford]

My ST50Tridata speed sensor unit failed recently. A previous thread on this site and even the Raymarine web site both note that you can't find a direct replacement for the ST50 , necessitating the purchase of the complete ST60 sensor and thru-hull unit and lifting the boat out of the water to install both. My local Raymarine dealer insists that he has found a replacement for the ST50 sensor unit which is the right OD (1 1/4") to fit into the existing thru hull fitting and can then be wired to the display using a junction box. It is $109 and should be here in a week. I will let you know how it goes.

[Mike and Joanne Stimmler]

If you're talking about your knot meter sensor, are you sure that the paddle wheel is clear and free to spin?

Mike

[John Langford]

Yup! And I even powered up the display while I was spinning it...

[Roc]

John,
I had trouble with my speed sensor.  Found out that the sensor is snapped together in two sections.  See if your sensor housing looks like to be put together in two parts (upper/lower).  On mine, the two parts were not tightly mated, and water got into it.  When it dried out, the sensor worked.  When put back in use, it worked for a while but quit after a certain amount of time.  What I did was after it dried out, I liberally put some caulk to seal the junction were the two halves meet.  That stops the water from entering. It's not a perfect fix, but it helps.  Also, if you take your sensor out when you leave the boat (so the paddle wheel doesn't get fouled), it's not sitting in water 24/7 and less likely for water to ender the unit.

Hope this helps....

[John Langford]

I couldn't get the old one to work even after drying it out for a few days. But I did install the direct replacement from Airmar (ST850/ Raymarine 2092P) which appears to be distributed by Geneco marine accessories (www.geneco.com or try www.airmar.com). It comes with the thru-hull housing which you can keep as a spare and works perfectly...at least when I test it out of the water by spinning it by hand. It even has the original fitting on the end which plugs into the vintage ST-50 plugs. Cost delivered was $109.

Routing the new sender from the forward berth to the Edson pedestal is no fun but it can be done cleanly with patience. My connections were made at the bottom of the Edson pedestal where a short cable from each instrument is connected to the longer cable from the sender unit.

[2ndwish]

We just completed the install of a RM ST6002 pilot on the pedestal guard rail. I agree, getting a wire through the 1" pipe through the cockpit floor was no easy task, but felt it was preferable to running even more wires through the pedestal itself, with all of the nearby moving parts. The wire penetrations through the floor (under the cover on the ceiling of the aft berth)  were potted with silicone and there wasn't much diameter in the cut to get another wire through. Thought about removing the pedestal guard altogether, but then realized with the original cabling, the entire pedestal would need to be disassembled. I eventually jammed a fiberglass fish tape (rapidly becoming my favorite $5 tool) through the silicone goop while my wife watched through the small wire hole in the guard until she could just see the top of the tape. Using a dental pick was able to hook the tape and get it out of the hole. Taped the new wire to the end and drew it back down. Does anyone know the proper way to seal the hardware at the bottom of the pedestal guard? Bedding the plastic hardware is insufficient since water can leak between the guard and the plastic fitting. The PPO seemed to use a lot of silicone inside and out. I'll get the pics off the camera tomorrow and show what our install looks like (in a separate thread).

[John Langford]

Followup to the earlier posts. The replacement ST50 speed sensor replacement worked perfectly in the water. So if your Tridata sensor packs in there is a cheaper alternative to replacing the whole unit.

[John Langford]

Update on the new sensor. During my recent cruise it began to work intermittently again. The online technical folks at Raymarine now say it is the display unit that is the problem despite the fact that the depth side of the unit works fine. They now recommend that I buy a new ST60 Plus display which they maintain will work with the ST50 Plus through hull speed and depth sensors.

I feel like I am slipping down the rabbit hole...first the new sensor and now the new display...

[Roc]

John,
Is your new thru hull paddle wheel one piece or is it two pieces?  What I mean about two pieces is there a groove where two halves snap together. Here is my original sensor.  Water got into the groove, between the two halves, and it worked intermittently.  This is the top half, the other section fell into the water when I pulled it out of the thru hull.  You can see, this came in two pieces.  The new sensors are one piece.

[Ken Juul]

If any of you that are replacing your speed sensors have a good paddle wheel can you send it to me.  My sensor still works, but the wheel is missing several teeth so turns intermittantly.

Thanks

[Mark Elkin]

I eventually jammed a fiberglass fish tape (rapidly becoming my favorite $5 tool) through the silicone goop while my wife watched through the small wire hole in the guard until she could just see the top of the tape. Using a dental pick was able to hook the tape and get it out of the hole. Taped the new wire to the end and drew it back down.

Whenever I have to deal with something like that, I always attach TWO items and pull them back through:
1. the wire/cable/line/etc that was the original purpose, and
2. an extra piece of line so that the NEXT TIME, there is already a pull line in place.

Just my 2 cents.

[Roc]

If you put a new speed sensor, you don't have to fish the new wire.  You can splice the new sensor to the already existing wire that is already on your boat.  Airmar said it was ok so I did it and it is fine.  Butt splice with shrink tubing to keep the moisture out.

[John Langford]

Ow! I wish I had thought of that before I fished the new sensor line from one end of the boat to the other! It is doable but not much fun.