Splicing knotmeter transducer cable...

[Mike Smith]

Last year I purchased a new ST60 knotmeter on EBay to replace the old one, which had died. I installed the display head at that time and connected the old transducer to it on the instrument cluster on the pedestal guard.  I had the new knotmeter transducer and bore installed during Breezer's biennial haulout last week.  The ST60 transducer bore has a neat flapper in it which prevents the stream of seawater gushing in when you pull the transducer out for cleaning.  The fore and aft conduit for the knotmeter and depthmeter transducer cables back to the instrument cluster is packed pretty tight. Instead of removing the old cable and snaking the new cable back to the instrument cluster, do you know of any reason why I can't I just cut the old cable at a convenient spot and splice the new transducer onto to the old cable?  I will probably use a junction box in the forepeak hanging locker.

Mike

[SteveLyle]

If it were me I'd call Raymarine and ask them.

Steve

[Roc]

A couple of years ago, my transducer actually broke right in half!!  Pulled it out to clean it and half came out and the other half was still stuck in the housing.  Water was coming in (slowly), so the only thing I could do is push it down and it did fall into the water......Well, I bought a new transducer and called Raymarine.  They said it was ok to cut the cable and solder the new one on.  I did that and it worked fine.  They said you can splice the knot transducer, but not the depth.

On a related note, my knot meter is not working again!  It's clean, but no data on the head unit (only zeros).  This was the same thing that was happening with the original transducer that ended up breaking in half.  Here's what I think is happening.  If you look at the transducer, you'll notice that it is acutally made in two halves that are snapped together.  When mine broke in half, I noticed that there are two metal mating surfaces that make contact and I noticed on the upper section, it was rusted.  Apparently, water can get into the seam and over time, it will corrode the connection between the upper and lower halves.  I believe this is what is happening with my 'newer' one, that has been in use for two seasons.  I will call Raymarine and tell them what my situation is, and when I replace the transducer, I plan on putting some below the waterline caulk along that seam to stop any water ingress.....I don't think it's right to have to buy new transducers every couple years....

[Stu Jackson]

Aye, and anyone else getting to just love Raymarine these days?

[Ron Hill]

Mike : You should be able to cut and splice that cable.  However, you need to call Raymarine and ask them which connector to splice in - so you don't have an impedance mismatch.   

[rirvine]

I have successfully spliced my depth, speed and wind transducer cables by soldering the wires and covering each wire with marine grade heat shrink.  They have been working without trouble for 4+ years.

[Mike Smith]

Ron -

I intend to use the Raymarine junction box that came with the unit, mounted high and to the left in the starboard hanging locker.  The individual wires will be cut and stripped and then inserted into the junction box terminals and screwed down.  There is no other connector involved.

Mike

[Roc]

Mke, there's a junction box???  I thought the cable went from the transducer directly to the unit on the pedestal??? 

[reedbr]

Mike-

I had a water-logged knotmeter and had to do the same thing.  I bought the ST60 transducer and spliced it to my ST50 head unit.  I did the splice using the junction box you mention under the V-berth as I think you planned.  The junction box doesn't need solder.  I kept it high to stay dry and kept a spare loop of cable on each side of the junction to avoid and strain on the connections.  The wires are small though.  Get a good stripper and a good light.  Instructions that came with the junction box or that I pulled off their web site (can't remember which) were good. 

Three years, no issues.

[Mike Smith]

I picked up six additional Raymarine junction boxes with SeaTalk connectors, cable, and ferrites for $70, shipping included, off EBay.  I removed four ferrites and attached them to my depth, speed, wind, and compass cables as they terminated at the ST400+ autopilot head.  I used two of the junction boxes to splice the depth and speed cables in the aft cabin, and will keep the rest as spares if I ever have to splice the wind and compass cables.  All of the cable wires are 22 guage and very delicate to strip!

Mike

[David Sanner]

I have a bit of a different story but somewhat on the same topic.

I purchased a new Standard Horizon knotmeter because my old display was bad.  I wasn't
planning to haul my boat for another 9 months but I decided to try the new display
with my old and completely different transducer.

I installed the new display, lobbed off the connector by the display and went about figuring
out, by trial and error mostly, which of each of the three wires from the old transducer went
to which of the four wires of the new display.   (I propped up the transducer next the the exhaust
from my shop vac to spin the wheel so I would be getting a signal when I got wires right).

I wasn't sure that they transducer was even compatible but eventually I got the right
combo and soldered everthing together.  A bit of luck was involved...

After my first test sail the knotmeter was reading too slow, even when I adjusted the
calibration to max.  I lived with this for a little while but eventually I decided I wasn't
going to be beat and decided to epoxy in another magnet to the paddle wheel to double
the signal.  After a couple tries to get the tolerances correct it worked too and I had
a working knotmeter.  I guess I should have just waited but I was curious and I've
always been impatient when it comes to waiting to use new toys.  (And a knotmeter
combined with a GPS can be handy when racing in the strong currents of SF bay)

This spring I finally installed the new/correct transducer and I now have temperature (cold) as well.
(That's what the 4th wire was for... and that little flapper to keep the water from rushing in actually works)

So, as others have said, you shouldn't have a problem cutting the cable, especially if you are
using the correct transducer.   If the colors of the wires don't match you know what to do... & good luck!