Transducer Frustrations

[islander20]

Hi everyone,

I just finished mounting my depth sounder display and wiring it up. I was feeling proud of myself until I tried finding somewhere to mount the transducer. Every spot of bare hull front to back was non responsive. To answer the easy questions, no my hull is not cored, I own a cal 20. The transducer worked perfectly when hung over the side. During testing the transducer was placed in a plastic bag of water. Next time I will try using KY jelly, I read that it is more effective. My hull does have a bit of a checkerboard pattern inside, definitely not smooth. I was considering sanding a spot for the transducer but I'm a little apprehensive about that and I don't want to have to sand half the hull till I find a good place. Any suggestions, I'm really stumped on this one?

PS there is no keel or other obstruction blocking it in the area I am trying to mount it in ( The aft storage section behind the quarter berths)

[Cheechako]

Hmm... I mounted one once with clear silicone, maybe pick a spot, take the paint off there and hold it on with silicone and see if it's working...? the checkered pattern you are seeing is the glass fabric, you probably have a lot of air pockets between your water bag and bottom of those little squares...?

[Roy M]

Agree. Unless the layup was extraordinarily crappy (air bubble voids), complete contact with the fiberglass is necessary for the transmission through the fiberglass hull. Use petroleum jelly, K-Y jelly, or anything that has no air bubbles to screw things up, and you should get a reasonable transmission. Best, cut the hole and install the transducer to the water, but sometimes...... Regardless, take the boat out and run it through the water to confirm that air bubbles, from turbulence down the hull, are not screwing up the reception of a good image on the MFD.

[KeysDreaming]

I had luck with putting mine in a mineral oil bath. Silicone did not work for me and was a pita to get off. Fashion a PVC pipe cut to the angle of the hull. Make sure it doesn't leak. Add mineral oil. Drop transducer in. Fill more oil. Cap

[KeysDreaming]

Originally Posted by KeysDreaming

I had luck with putting mine in a mineral oil bath. Silicone did not work for me and was a pita to get off. Fashion a PVC pipe cut to the angle of the hull. Make sure it doesn't leak. Add mineral oil. Drop transducer in. Fill more oil. Cap

Forgot to mention. Epoxy PVC in place. Haha

[Cheechako]

I have just epoxied a puck inside a hull 1.25+ thick and the sounder read to 600 feet.... I guess you just need to confirm it's working before doing that.....

[donradcliffe]

I tried silicone and it didn't work. A water box inside the hull worked fine. I would try the PVC pipe with fresh water instead of oil.

[Roy M]

Propylene glycol also is good, AFTER you have determined the best site for the transducer. Remember, it's the bubbles flowing down the hull line that can give you screwy readings. Take the boat out first, when possible, to confirm that your potential site will work well.

[noelex 77]

The plastic bag should work. Maybe the pattern on the fiberglass is trapping some air under the bag. Try building a little dam with blue tack and wetting the fiberglass it only has to deep enough to cover the pattern. Then put the plastic bag over the wet fiberglass. If this does not work I would be doubtful a permant instalation with any of the, normally good, methods suggested would work any better.

[islander20]

Just to put an end to this thread if any stumbles upon it, I finally got it to work! Had to sand the inside of the hull till it was smooth. Either the paint or bumpy fiberglass was the problem. So nice when something actually goes right on a boat.

[micah719]

Just an obscure curiosity.....what's the maximum depth it can measure?

[islander20]

Well I was in 17 feet of water at the marina today, didn't have a chance to take her out. I'll check next time I'm out.

[micah719]

Cool, thanks. Btw...what is the true depth under the lowest part of the boat, compared to the readout; and what effect will heel have on the measurement. Sry, still curious. Must have cat-genes.

[noelex 77]

Glad you got it working and it's nice to know the reason.

Originally Posted by micah719

Just an obscure curiosity.....what's the maximum depth it can measure?

I installed an internal transducer in my last boat and a side by side comparison with the same unit externally mounted showed it lost about 1/3 of its maximum depth reading. It was also more erratic than the externally mounted transducer, but the results will depend on the fiberglass layup.

In some parts of the world deep readings are very helpful. My current B&G depth cut out is typically about 220m (720 feet) which is a big improvement over the identically mounted Raymarine unit which cut out at 1/2 of this.

[Mike Banks]

The ones which read greater depths usually draw more current too. Through-hull types usually work best--but I do not like too many holes in the hull. The oil in the PVC pipe cut to fit the hull and standing vertically works for me. If it gets into the transducer it may still work--water eventually kills them I think. I have a couple of perfectly good instruments with dead transducers. I do not think this system works with steel hills though.