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Author Topic:   SONAR Transducer Roostertail
eportfolio posted 04-02-2006 09:06 AM ET (US)   Profile for eportfolio   Send Email to eportfolio  
While out on the water yesterday, I noticed that I had a lot of water kicking up, spraying from the starboard side of my transon. This happened while under half and full power, always when planing. It didn't seem to be kicking up water on the port side of the transom.

The only item I have mounted on the transom is a depth finder, but I can't imagine it would have caused that much spray.

Any thoughts?

Teak Oil posted 04-02-2006 09:22 AM ET (US)     Profile for Teak Oil  Send Email to Teak Oil     
I have seen some transducers kick water 6 feet straight up in the air depending on their design and mounting height. If the transducer is correctly mounted you should be able to run a straight edge along the hull and the transducer with no gaps at all.
jimh posted 04-02-2006 10:52 AM ET (US)     Profile for jimh  Send Email to jimh     
A good way to observe the cause of the rooster tail is to look over the transom while the rooster tail is being created and see where it comes from.

It sounds like the SONAR transducer is causing it.

minitauk85 posted 04-02-2006 05:14 PM ET (US)     Profile for minitauk85  Send Email to minitauk85     
eportfolio-This is a pic of the rooster tail my Humminbird transducer puts off. I still need to mount it at the right height but am afraid to do so as the mount appears to be glued to the hull-k
Fishcop posted 04-02-2006 05:49 PM ET (US)     Profile for Fishcop  Send Email to Fishcop     
Sounds like the transducer mounting height. Give us some more details or photos and we can help.


gss036 posted 04-03-2006 12:38 AM ET (US)     Profile for gss036  Send Email to gss036     
What kind of transduecer is it? I put out a pretty good rooster tail on mine also, it is high spped Eagle/Lowarence. I have played with different mounting positions and still can't get rid of it. I will try another, deeper position in the next month or two to see what happens.
Keep us posted if you figure it out.
Sal DiMercurio posted 04-03-2006 12:14 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
If your transuducer is mounted correctly, you "WILL" get a rooster tail from it.
In order for your transducer to be able to send out & recieve sonar signals, the bottom of the transducer has to be 'IN" the water about 1/4" or even more in some cases.
If it is perfectly level with the bottom, the water coming off the bottom will have air bubbles in it & you will loose your signal at anything over planing speed.
The reason my sonar reads perfect at 60 mph is, it's mounted below the bottom of my boat by 1/4" & yes, it does throw a rooster tail even though it's a high speed transducer.
The is an adjustment on the bracket of your transducer, just loosen the small bolts & either lift or lower the TD to where it still reads at high speeds but gives the smallest rooster tail.
You just have to experiment with it.
Sure, you can eliminate the rooster tail but you will also loose your signal once your on plane.
Jerry Townsend posted 04-03-2006 01:10 PM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
But then mounting the transducer below the plane of the hull generates turbulence, and turbulence creates an erroneous signal for "sonar" systems. That is the reason that the instructions for my (BottomLine) "sonar" specified that it be mounted at the same depth as the hull at that location. Now, my "sonar" is quite old (maybe 20 years) - and that specification may no longer be made as many improvements in electronics have been made in that time period.

Now, I have not seen a noticable rooster-tail from the transducer - but then, I am not going 60 mph - hell, Sal I would have to mount a J-57 jet engine to do 60 mph. What in the devil are you running anyway? ---- Jerry/Idaho

eportfolio posted 04-03-2006 05:00 PM ET (US)     Profile for eportfolio  Send Email to eportfolio     
It's a transom mounted transducer designed for high-speed operations. Eagle says "The Skimmer® transducer design performs best when it is slightly below the boat's hull."

This is where mine is located, so maybe it's ok. I just wanted to verify that this was something I should expect, and not be concerned about. At first I thought it was a problem, but it sounds like it's normal after reading your posts.


davej14 posted 04-03-2006 06:55 PM ET (US)     Profile for davej14  Send Email to davej14     
It is pretty easy to adjust. Why not raise it up a bit and see what happens to the performance at high speed. If it doesn't work just move it back and live with the rooster tail. My Lowrance skimmer works at plane without a rooster tail.
Sal DiMercurio posted 04-06-2006 10:51 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Jerry, I'm running a 1979 - "V"20 Outrage that's recommended for 180 hp maximum, but my 2000 - 200 hp Evinrude DFI is putting out 222 hp at the prop.
When I raise my engine up to the 3rd set of holes [ for running on the Sacramento river ] & put a Stiletto 14.25 x 21 s/s prop on & remove the kicker, 1 - 60 lb battery & all the extra heavy things that are in the boat & only 6 gallons of fuel she will twist the prop on 18" chop to 6100 rpms,...100 rpms under the over rev automatic shut down rpm.
She was shot on police radar on 3 different runs turning 60.8 - 60.3 - & 60.8 mph trimmed out to maximum.
As she sits right now with a 19p stiletto extra cupped [ for the ocean ] & down on the 2nd set of holes & an 80 lb kicker sitting next to her with a portable 6 gallon tank for the kicker & 30 gallons in the tempo under the seat, & all the rest of the crap in the boat she will get 56 - 58 mph on slight chop water,...only 55 on flat calm water.
I've got 1600 hours on her with less than 10 minutes at WOT according to the computer.
My cruise rpm is 3000 - 3500 which gives me 30 mph to 34 mph.
Seems the tach [ with the 21p prop ] reads darn near the exact speed as the speedo, gps & sonar,..example, 3500 rpms = 35 mph,...4000 rpms = 40 mph 5500 rpms = 55 mph
jimh posted 04-06-2006 11:09 PM ET (US)     Profile for jimh  Send Email to jimh     
Using the LOWRANCE Skimmer transducer, it should be possible to get both good bottom echoes at speed and minimal spray from the transducer. A typical installation will only create spray a few inches high coming from the transducer wake in the water.
17 bodega posted 04-08-2006 02:48 AM ET (US)     Profile for 17 bodega  Send Email to 17 bodega     
When taking Jimh's advice above and looking over the transom, make sure you still look where you're driving the boat. Most fishing boats I've gone fast in have a nice rooster tail fromt the sonar transducer. Foggedabouditt... go get some fish!

I have the LOWRANCE big type of skimmer. I figure if it reads the bottom correctly, I'm good.

Tom W Clark posted 04-08-2006 10:52 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
The LOWRANCE Skimmer transducer is FAR superior to the old fashioned V type transducer. It will both hold the bottom better AND not throw much, or any spray. I have owned several of them.

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