Transducers - Through Hull or not?

[cbadmin]

From: Mike (Original Message) Sent: 12/1/2002 10:18 AM
From: Mr Fisherman (Original Message) Sent: 12/1/2002 12:17 AM
Transducers that is. I haven't mounted either one but hope to have the opportunity soon. I know that if ya want to have accurate display at cruising speed or if you have an inboard motor through hull is the way to go. How about it, anybody have experience mounting this type of unit on a C-Dory hull? Les, anyone?

From: Mike Sent: 12/1/2002 1:51 PM
Ray -

It seems to me that for a thru-hull on a CD, you have to bore through the inside layer of glass and the balsa wood core to get the transducer to see through the outer layer of glass. I know there are methods of doing so and resealing without compromising the hull integrity, but dang, that sure sounds like a big, deep hole. Of course, I am the nervous type.

The sounder I am using is a low-end Humminbird with a transom mount transducer. It does go goofy at cruise speed once in a while, but usually works just fine. I also noticed that when the detpth gets over 200', the readings can be erratic (sounder is rated to 600'). That may have more to do with the angle of the transducer than the mounting.

Mike

From: Mike Sent: 12/1/2002 2:39 PM
Since we're on the subject, what is it that makes the thru-hull more accurate? Stability, or just getting away from the turbulence?

Greg - You mounted a transducer via a cutout in one of your trim tabs. How is that working? I can see it being steadier than the transom mount, and a little farther out of the turbulence of the prop. Does the changing angle affect its readings any?

Mike

From: LesLampman Sent: 12/1/2002 3:29 PM
Hi,

I don't believe that thru-hull transducers are in and of themselves more accurate or "better" than transom mount transducers. Through hull transducers are necessary on inboard powered boats because they won't operate in the propwash from an inboard if mounted on the transom.

Transducers work by sending out sound waves; they don't get a return from that sound wave if it hits air (or highly aerated water). Transom mount transducers do need to be mounted properly and getting the correct "height" relative to the transom is important. Of course a poorly mounted transom mount just doesn't work well; a poorly mounted thru-hull transducer just fills the boat with water .

I just tested a transom mounted Airmar P66 transducer (Garmin 2010C) yesterday at 30 knots in a couple of hundred feet of water; it worked perfectly. With that kind of performance I wouldn't even consider taking a hole saw to the bottom of a C-Dory. And, BTW, the C-Dory is one of the easier boats on which to get a transom mounted transducer working well; it doesn't have a sharp "V" and it isn't very fast. My favorite transducers are the Lowrance Skimmer transducers and the Airmar P66 transducers (they are used on Garmins, Furuno and other units).

Les

From: Redƒox Sent: 12/6/2002 1:41 PM
http://www.msnusers.com/CBratsOnline/tipsamptricks.msnw?action=ShowPhoto&PhotoID=827

UP THERE ^^^^^^ to see the (through tab) mounted transducer!

Yup it was my brainstorm and by golly she works better than any other transducer to date. Problem was, I was always banging-up the thing, that's what got me to thinking about through mounting it here!


From: Sawdust Sent: 12/6/2002 3:40 PM
Greg,

I used the same idea with a huge commercial transducer several years back. That rascal weighed about 4 or 5 pounds - it was for a big Furuno commercial application and the guy decided he wanted a different one. Worked great unless I put the trim tab full down, at which time the echo return from the downrigger balls was so strong it wiped out the whole screen. Otherwise it worked great, and I thought I might do it again... but cutting a hole the right size in the stainless tab was not a job I wanted to tackle. And I couldn't afford one like that now... as a dealer I got stuck with it, so used it until I sold it to another commercial fisherman. Another problem, when it pulsed you could feel it throughout the boat, but that would happen no matter where it was installed - and of course it took a big battery to keep it going. I really like your installation though, and not a bad idea to just put on an extension like you did and go for it.

Dusty

From: Redƒox Sent: 12/6/2002 10:24 PM
Wow Dusty, ya done beat me to it.
Loved your story, glad you posted it my friend! The thing is not perfect but certainly works much better than anything else I have had on there.