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Any of you B20 guys have a good spot for a transducer? My transom mount loses bottom at 12 knts. It was on there when I got the boat. I moved it, and almost the same result. With 3 strakes per side, and an OB, and that narrow beam, there doesn't seem to be much clean water. I've tried a new transom-mount with the same result, so its not the transducer. I stuck the ducer in a baggie filled with water and held it in my bilge, and got it to read to about 20 knots. I think I'm going to go with a bronze flush thru-hull in that location.

Any advice would be appreciated.

The transom mount on my Whaler holds bottom to 35 knts or so, and the bronze thru-hull on my B31 held bottom to at least 30 knts. This is getting frustrating.

You might want to consider an Airmar inside the hull transducer. They're adjustable for hull angle up to 22-24 degrees. The actual transducer sits in anti freeze you put in after mounting the container. I put mine just a bit forward of the engine hatch on the starboard side. Conceptually, pretty much like your bag of water. They used to use glycerine for the liquid but switched to anti-freeze as the glycerine was doing a number on the gaskets. The important thing is no bubbles.

Walter-

The electronics guy showed me that as an alternative to a thru-hull. At what speed do you lose bottom?

Thanks-

John

I'm guessing in the 20's. I'm not crazy about my DR so I'm not sure who's fault it is. The best part is nothing sticking out below. For positioning, I'd experiment to see if one place got you better performance than the other with the bag of water. Actually I was told you could silicone a transducer to your bottom inside. The key is no bubbles.

Thanks Walter.

John - I have a shoot-thru-the-hull on my B31 hooked up to a Garmin black box sounder, think its a 500 watt model and it holds bottom fine at 24 kts up to about 250 feet. Very easy to install - first put the 'ducer in a zip lock bag of water and place it in various spots to check your reception, then when you find the right spot, just grind away the crud, place the cylinder holder on the bottom, level it up (a mini level works good), then draw two concetric circles with a magic marker. Run a bead of 4200 between the circles and press the cylinder down and put something on it until the 4200 sets up. Then fill the cylinder with mineral oil, put the ducer in and lock the top. Mine has been in for 10 years with zero problems.

UV

John- Vic is right, it was mineral oil, not glycerine. Airmar did however suggest changing to Anti-freeze, but sure sounds like Vic's 10 yr trial hasn't affected his gasket/o rings.

I just installed a flush mount transducer that has the angle built in. Was an excellent choice for me as I already had a thru hull tranducer I wanted to get rid of.

How it works...I'll find out later today when I get splashed. Reall nice to get those big transducers off the bottom of the boat.

Have a tranducer in the hull too. It's my backup...I just leave in a bag of water all summer then empty the bag for the winter. I was going to epoxy in place permantetly, but it works real good just the way it is and why mess with good...

Thanks again. I think up here where it freezes in the winter they started recommending anti-freeze. That's what my electronics guy said anyway.

I got a shoot-thru today. I was wrong--electonics guy said use mineral oil or AF, and that neither would freeze. The shoot-thru was cheap--$79.

John - I got my mineral oil at the drug store and it does not take much - one little bottle was enough for mine. We are lucky in that our old Bertrams all have solid glass hulls so the shoot-thru works fine....won't work on a cored hul, but on the other hand, a cored hull ain't gonna last long enough to worry about replacing anything anyway.

UV