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Author Topic:   Transducer Rooster Tail
densefog posted 06-03-2009 02:22 PM ET (US)   Profile for densefog   Send Email to densefog  
I installed a [Humminbird] SONAR transducer according to the manual on the transom of my [1988 Boston Whaler SUPER SPORT 13], and it kicks water when the boat gets above 30-MPH. I hate drilling more holes than necessary, so any advice would be greatly appreciated.


GreatBayNH posted 06-03-2009 04:40 PM ET (US)     Profile for GreatBayNH  Send Email to GreatBayNH     
Search this site. Many results. Here is one of them.

Dan posted 06-04-2009 07:45 AM ET (US)     Profile for Dan  Send Email to Dan     
try adjusting the angle of the transducer, same position, different angle
Jefecinco posted 06-04-2009 09:57 AM ET (US)     Profile for Jefecinco  Send Email to Jefecinco     
Or, you could ignore it. Is it causing any harm? Do you get good readings above 30 MPH? If you are a salt water boater and the rooster tail is spraying on your engine you may want to adjust the xducer angle a bit. If you are getting good readings you probably do not need to change the mounting height.

If you decide to change the mounting height use some Starboard Marine Lumber to fabricate a mounting surface for the relocated xducer. The Starboard will have to be mounted to the tramsom but you can then change your xducer multiple times without again drilling into the transom.


New 2 Whalers posted 06-04-2009 05:53 PM ET (US)     Profile for New 2 Whalers  Send Email to New 2 Whalers     
If you installed it according to the manufacturer's instructions a rooster tail shouldn't be a problem. I seldom rely on mine for an accurate bottom read at 30MPH. I rely on the GPS at speed and the fish finder when I am slowly searching the bottom depths and it works great:-)

Happy fishing.

densefog posted 06-04-2009 11:10 PM ET (US)     Profile for densefog  Send Email to densefog     
To Great Bay and Dan, I took the advice given here and adjusted the angle and fabricated a 5 inch lexan shield which now keeps water off the engine and out of the boat, thank you very much. But the sonar reading is a constant 0.7 feet at any speed above 10 mph. Knowing if the bottom surface I'm running over is mud or an oyster bed is rather inportant when you just repowered with a new Honda 50. I've read that thru hull tranducers only work for hollow hulls, otherwise I'd go that route. Butch, do you attach Starboard with Marine Tex? I appreciate the input.


Jefecinco posted 06-06-2009 10:20 AM ET (US)     Profile for Jefecinco  Send Email to Jefecinco     

I use screws to attach the Starboard to the transom. Before doing so I'd fill the existing xducer mounting screw holes with a good caulk such as Boat Life Caulk. I'd also apply a few strips of the caulk to the Starboard before attaching it to the hull. I'd pay particular attention to ensure the new Starboard mounting screws and holes are well coated with the caulk. I also use the caulk to seal around the edges of the Starboard where it contacts the transom. It is probably not necessary but looks better when done.

I'ts important to use Starboard of sufficient thickness to accomodate the full length of any screws you'll use to mount the xducer.


Dan posted 06-07-2009 07:19 PM ET (US)     Profile for Dan  Send Email to Dan     
Dave, if the reading is wrong at speed you must have turbulence. Maybe from the starboard if it extends past hull. I was recommending keeping the transducer in the same spot and just loosening the screw to adjust the angle.
densefog posted 06-07-2009 11:15 PM ET (US)     Profile for densefog  Send Email to densefog     
So my next question is where on the transome would the water not be turbulent? I've not changed the location only adjusted the pitch and depth.
Jefecinco posted 06-08-2009 08:49 AM ET (US)     Profile for Jefecinco  Send Email to Jefecinco     

The instructions with your Hummingbird should have discussed how to select a good mounting location. If they did not you can check the Lowrance web site and refer to the down loadable manuals for sounders where the information can be found.

As I recall the xducer should be mounted a couple of feet from the propeller and at a position on the transom where it intersects a flat area of the hull, ie. not behind a strake or other irrugularity.

It should be mounted so that a straight edge placed flat along the hull length would also be flat along the xducer face. The idea is to have the smoothest possible transition from the bottom of the hull to the face of the xducer. When mounted in this initial position the xducer mounting bracket should be positioned to allow some adjustment of the xducer in the bracket for "fine tuneing".

If after mounting the xducer in the recommended fashion porformance is not satisfactory a final adjustment will be required. I believe the best way to make a final adjustment is to have a friend operate the boat while you observe water flow under the xducer while on plane. The friend can report the sounder's reaction to any adjustments you make. In a few minutes you should be able to make any adjustments to provide satisfactory performance.


jimh posted 06-08-2009 09:20 AM ET (US)     Profile for jimh  Send Email to jimh     
Here is a view of the mounting of a transducer on the transom of a boat with a moderate v-hull. This location produced good results from the sounder along with minimal splash or rooster tail from the transducer: transducerMountingCloseUp.jpeg

For some more information on transducer mounting location on the transom of moderate v-hull boats, see:

densefog posted 06-08-2009 09:09 PM ET (US)     Profile for densefog  Send Email to densefog     
Jim when I had a Lowrance m56/s the xducer was installed just like in the photo and worked just fine until the original Johnson 40 died. For some reason once the HONDA 50 was installed, it never gave an accurate reading again. I rerouted the wires direct to the battery to remove the possibility of electrical interference but no change. So I replaced it with a Humminbird combo which states that the xducer should be a minimum of 15 inches from the prop so I patched up the holes for the Lowrance and moved starboard as directed. Is a Thru hull xducer possible? Butch, I'm not leaning over my transome when any of my friends are steering.
Jefecinco posted 06-09-2009 09:58 AM ET (US)     Profile for Jefecinco  Send Email to Jefecinco     

A through hull is certainly possible but a "shoot-through-the-hull" would be my preferance. A shoot through will not shoot through foam so ideally if there is a place in your bilge which is solid laminate that would be the place to mount a shoot through xducer. By the way, your existing xducer should work well as a shoot through. If an area of solid laminate is unavailable a shoot through remains a possibility. But, you will have to cut through the inner hull (liner?) to the foam, remove the foam, reseal the inner hull to the outer hull around the perimeter of the new hole in the liner. The xducer can then be attached to the inside of the outer hull.

There are fancy, special methods for attaching the xducer to the hull. However, I've had very good results by simply using a good quality caulk for this purpose. Before attaching it would be wise to test the setup. This can be done by placeing the xducer in a plastic food bag filled with water. The bag opening can then be secured tightly to the xducer cable with some good electrical tape. The transducer can then be placed on the surface where it would be mounted and then the arrangement can be tested.

Generally, if performance is good while the boat is at rest it will be good while underway or at high speed. If you want to test it at speed some duct tape could be used to hold the xducer and water bag in place.

If you are satisfied with the test results and wish to use caulk it is very easy. Use a good quality caulk and form a large, deep puddle at the mounting location. apply the caulk so bubbles are not formed. The idea is to have no air spaces between the xducer and the hull. Then, slowly push the xducer into the caulk puddle until it contacts the hull. Ensure the xducer angle is as vertical as possible. Then secure it in place with materials prepositioned for the purpose. If your hull angle is a little extreme you could do a dry run attempt to secure the xducer before proceeding with the caulk.

I've used this method on two previous boats and the outcome was perfect.

Having said all the above I believe you can find a way to make your transom mounted xducer set up work well and that would be the preferred solution. Reading your last comment it is not clear to me if you have reused the Lowrance xducer or installed the new Hummingbird one. If you're using the old xducer consider changing to the new one.


1985supersport15 posted 06-09-2009 07:37 PM ET (US)     Profile for 1985supersport15  Send Email to 1985supersport15     
densefog, How old is your transducer bracket?

I had a similar problem with mine purchased in 2008. My problem was that the water would shoot up through the gap between the transducer and the bracket. if your purchase is recent you can call humminbird and tell them your dissatisfaction with the design flaw. they sent me a rubber blocker that they fabricated that fits right between the transducer and the bracket.

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