Speed Log transducer types

[joewalsh]

Hi,
I recently purchased and installed a new NASA Dual speed/log and Depth system. After installing the display I realised that the Transducer was smaller that the previous one that I was replacing. I don't have the Option to change the skin fitting on the boat. is there any alternative to replacing the skin fitting or having to go with a Speed log with a different ( larger) transducer
Best Regards
Joe

 

[William_H]

Sorry I don't know the NASA in detail. However the first question is will the existing transducer do the job. How many wires does the NASA use . Some will be a simple switch which makes contact in the presence of the magnetic field of the rotor. Others might use a Hall effect transistor to sense the magnetic field. The first will need only 2 wires often an outer shield and an inner core. Sometimes 2 wires and a shield. The latter type might need a 5v supply on one wire and a signal out on the other plus a shield /earth return. You could check the NASA wires for a voltage.
If you decide that the transducers are compatible then you need to cut wires and probably change plugs. Then you may find that the original transducer is not working often due to deterioration of the magnets in the rim of the rotor.

So all in all probably you will have to fit the NASA transducer. You could repair the old hole by filling it. Lots of description on this forum and bore a new hole in the repair opr a completely new hole.
For my opinion however I long ago removed my paddle wheel log and filled the hole. I live ina an area of warm water so frequent fouling of the paddle . It was just too muc trouble to keep it working and a GPS has replaced it. good luck olewill

 

[joewalsh]

Hi
One other question, I have time to change the skin fitting over the weekend but the new (NASA) fitting is smaller than the Old ( ECHOSOUNDER) one. any advise on how to approach this. Seal and rebore a new hole or fit the new skin in the existing hole and secure it using Glass Fibre???
Thanks
Joe

 

[prv]

Seal and rebore a new hole or fit the new skin in the existing hole and secure it using Glass Fibre???

I think any approach involving glueing the skin fitting into an oversize hole will be a bodge, quite possibly a dangerous one. I once had a transducer pop out of its fitting at sea, we had water up above the bunks in no time and the hole if you lose the whole fitting will be bigger.

You will need to grind a wide taper around the hole, preferably on both inside and outside, and fill with plenty of layers of cloth/mat and resin. Lots of more detailed instructions out there if you google. Then drill a new smaller hole and fit the transducer according to the instructions - some want glassing in as well as just screwing.

Pete

 

[xeitosaphil]

Hi
One other question, I have time to change the skin fitting over the weekend but the new (NASA) fitting is smaller than the Old ( ECHOSOUNDER) one. any advise on how to approach this. Seal and rebore a new hole or fit the new skin in the existing hole and secure it using Glass Fibre???
Thanks
Joe

You don't actually say what sort of echo sounder you are replacing. You may find that the transducers are compatible even though their physical sizes are different. I once fitted a Nasa Target 2 Echo Sounder, which was a replacement for a Seafarer 7, and found that the new display unit was compatible with the old transducer, and kept the new one as a spare. The only thing was I had a separate speed log.

I personally don’t think it’s a good idea to use a bigger hole to fit a smaller transducer in, chances are you will always have a potential problem waiting to happen. I would suggest fitting the new smaller transducer in this weekend in a new position and leave the old one in place. Then at the end of the season when you have more time, remove the old one and do a proper hole glass fibre repair.