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Author Topic:   Whaler Drive SONAR Transducer Location

GTL posted 05-29-2009 09:25 AM ET (US)
Have an Outrage 22 Whaler Drive and an Airmar P66 SONAR transducer is mounted on starboard side of the Whaler Drive just below the skeg line. The depth finder looses bottom as soon as boat goes on plane. I believe I can lower mounting of Transducer about 1/2-inch. Would moving it closer to the keel help? [Give] recommendations on how to hold bottom. I think the step up from hull to Whaler Drive causes turbulance which kills my depth finder. Is there a better transducer?
jimh posted 05-29-2009 09:48 AM ET (US)
I am not familiar with the term "skeg line." Perhaps you could elaborate on what it means.
I have a Boston Whaler boat with a Whaler Drive. When I first acquired it, the SONAR behaved as you describe. It would lose the bottom echo easily when the boat was on plane. The remedy was to move the transducer location. The transducer was originally located rather far outboard from keel centerline on the Whaler Drive. I moved it closer to keel centerline.
I do not have measurements available at this writing, however you can see the general location of the SONAR transducer on my Boston Whaler Whaler Drive in the picture linked below:
http://continuouswave.com/whaler/reference/images/ETEC250HO/ offWithOld640x422.jpg
The distance from the keel centerline to the transducer is probably about 14-inches. I think this is in keeping with a general recommendation that the SONAR transducer should not be any closer to the motor so that it will not disturb the flow of water into the motor. On a Whaler Drive boat this is not particularly cogent because the Whaler Drive itself does a good job of disturbing or aerating the flow of water into the propeller.
Since I moved the transducer inboard and closer to keel centerline, it has performed much better. I now can hold bottom echoes while on plane and going as fast as 50-MPH. The bottom echo is certainly not as strong or as distinct as when off plane, and you cannot expect to see fish echoes, but you generally do not lose the bottom. Of course, the water depth plays a part. In my case the water depth is generally less than 100-feet. If you are in deep water your ability to maintain the bottom echo might suffer more when the boat is on plane.

TransAm posted 05-29-2009 09:48 AM ET (US)
It is normal for you to loose data readings from a transom mounted transducer when you are traveling on plane. Generally speaking, mounting the transducer close to the keel it is not recommended. Thru-hull transducers are generally better at holding data readings while on plane.
jimh posted 05-29-2009 09:53 AM ET (US)
It is my experience that the depth of immersion of the SONAR transducer into the water is very influential on how well it works when on plane. If the transducer is not immersed into the water when the boat is on plane you will suffer loss of return echoes. In this regard a change as little as 0.25-inch in the vertical position can mean the difference between good echoes and no echoes when on plane.
TransAm posted 05-29-2009 09:59 AM ET (US)
For clarification, it would depend on whether you have a single or dual engine set-up. With twin engines, you should mount a transducer between the motors but not directly on the keel (your Whaler-drive should be flat so no worries). If you have a single motor, most recommend mounting on the starboard side several inches beyond the radius of the prop. On-plane results will vary; a thru-hull transducer will generally provide better performance.
GTL posted 05-29-2009 10:12 AM ET (US)
Jimh--Thanks for the picture. My transducer is [outboard] of yours; [it is located] below the bolt heads that hold on the [Whaler Drive.] [I] believe the [Whaler Drive] has a step towards the transom right there, thus my transducer is right at that change.
I believe I can gain a 1/2-inch by moving the transducer down, but will require drilling another set of holes. I'm glad I asked. Think I'll mover it closer to the keel as shown in your picture and see what happens.
I also have a single 300 HP Suzuki; just love it. [I hope] to get reading when on plane, but at 50 MPH, I'm glancing at the tachometer and the GPS for speed and holding on for dear life.
Would like to use a through-hull transducer, but don't really want to drill [large] holes through my hull. Has anyone [installed a through-hull SONAR transducer in a Boston Whaler 22-foot hull] with great success?
Thanks for the information, been a great help.
TransAm posted 05-29-2009 11:21 AM ET (US)
I am considering a thru-hull transducer for a couple of reasons as I need to replace my fishfinder/sonar unit. The first, as has been mentioned, is the ability of the unit to transmit data while underway at higher speeds. The second is that a thru-hull transducer is not subject to being knocked around and damaged sitting exposed on the transom.
Having just replaced both stern thru-hull brass drains, I am much less concerned about drilling another hole in the hull because of the technique I used. A picture is worth a thousand words, so I'll try and post a diagram. I have seen this technique before, perhaps here of on another site. I did 2 of these in about an hour and a half including the removal of the old brass tubes.
http://s299.photobucket.com/albums/mm314/77SETransAm/?action=view& current=Thru-hull.jpg

The addition of Epoxy completely seals the hull and prevents water from entering the foam. Simply slide the thru-hull in the bottom (you will need a fairing block which often comes with the set-up), seal it with some 5200 and you are good to go.
GTL posted 05-29-2009 03:16 PM ET (US)
TransAm: Know you are local, (I live in Davidsonville,MD) so I'd like to see when you put in the Through Hull Transducer ....Please take lots of picture, I like to do that my self, just a little adverse to drilling holes in the hull.
Right how, I'm going to move my transducer to a similar position that JimH showed in his picture ... I'll post back with the results
Thanks
TransAm posted 05-29-2009 03:24 PM ET (US)
I drive through Davidsonville almost every week in the summer down to my summer house in Beverly Beach. I'll keep you posted.
jimh posted 05-29-2009 08:33 PM ET (US)
ASIDE: If you need help with authoring on this forum, please see the information in the pages linked under "author help." A hyperlink appears on every page.
GTL posted 05-31-2009 04:54 AM ET (US)
Well, moved my transducer to the approximate location shown in JimH's pictures. Ran the boat yesterday and the depth finder held bottom the whole time, even at speeds in access of 40 MPH. At higher speed, it lost the ability to find fish, but knew the water depth. Thus I wasn't concerned about running aground.
Thanks for the help. Now to fill the old mounting holes with gel coat.
jimh posted 05-31-2009 10:45 AM ET (US)
Thanks for the follow-up to let us know the outcome. It sounds like you have moved the SONAR transducer to a good location on the Whaler Drive.
Slippery Eel posted 06-02-2009 10:36 AM ET (US)
I installed a new Raymarine unit on my 22 Revenge with Whaler Drive this spring. I have either the P58 or P88 Airmar transducer. The instructions called for it to be mounted within 3" of the prop diamater. I followed this and found it works fairly well at all speeds.
I still lose the signal occasionally on a sharp turn or in reverse due to prop wash.

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Author	Topic: Whaler Drive SONAR Transducer Location
GTL	posted 05-29-2009 09:25 AM ET (US) Have an Outrage 22 Whaler Drive and an Airmar P66 SONAR transducer is mounted on starboard side of the Whaler Drive just below the skeg line. The depth finder looses bottom as soon as boat goes on plane. I believe I can lower mounting of Transducer about 1/2-inch. Would moving it closer to the keel help? [Give] recommendations on how to hold bottom. I think the step up from hull to Whaler Drive causes turbulance which kills my depth finder. Is there a better transducer?
jimh	posted 05-29-2009 09:48 AM ET (US) I am not familiar with the term "skeg line." Perhaps you could elaborate on what it means. I have a Boston Whaler boat with a Whaler Drive. When I first acquired it, the SONAR behaved as you describe. It would lose the bottom echo easily when the boat was on plane. The remedy was to move the transducer location. The transducer was originally located rather far outboard from keel centerline on the Whaler Drive. I moved it closer to keel centerline. I do not have measurements available at this writing, however you can see the general location of the SONAR transducer on my Boston Whaler Whaler Drive in the picture linked below: http://continuouswave.com/whaler/reference/images/ETEC250HO/ offWithOld640x422.jpg The distance from the keel centerline to the transducer is probably about 14-inches. I think this is in keeping with a general recommendation that the SONAR transducer should not be any closer to the motor so that it will not disturb the flow of water into the motor. On a Whaler Drive boat this is not particularly cogent because the Whaler Drive itself does a good job of disturbing or aerating the flow of water into the propeller. Since I moved the transducer inboard and closer to keel centerline, it has performed much better. I now can hold bottom echoes while on plane and going as fast as 50-MPH. The bottom echo is certainly not as strong or as distinct as when off plane, and you cannot expect to see fish echoes, but you generally do not lose the bottom. Of course, the water depth plays a part. In my case the water depth is generally less than 100-feet. If you are in deep water your ability to maintain the bottom echo might suffer more when the boat is on plane.
TransAm	posted 05-29-2009 09:48 AM ET (US) It is normal for you to loose data readings from a transom mounted transducer when you are traveling on plane. Generally speaking, mounting the transducer close to the keel it is not recommended. Thru-hull transducers are generally better at holding data readings while on plane.
jimh	posted 05-29-2009 09:53 AM ET (US) It is my experience that the depth of immersion of the SONAR transducer into the water is very influential on how well it works when on plane. If the transducer is not immersed into the water when the boat is on plane you will suffer loss of return echoes. In this regard a change as little as 0.25-inch in the vertical position can mean the difference between good echoes and no echoes when on plane.
TransAm	posted 05-29-2009 09:59 AM ET (US) For clarification, it would depend on whether you have a single or dual engine set-up. With twin engines, you should mount a transducer between the motors but not directly on the keel (your Whaler-drive should be flat so no worries). If you have a single motor, most recommend mounting on the starboard side several inches beyond the radius of the prop. On-plane results will vary; a thru-hull transducer will generally provide better performance.
GTL	posted 05-29-2009 10:12 AM ET (US) Jimh--Thanks for the picture. My transducer is [outboard] of yours; [it is located] below the bolt heads that hold on the [Whaler Drive.] [I] believe the [Whaler Drive] has a step towards the transom right there, thus my transducer is right at that change. I believe I can gain a 1/2-inch by moving the transducer down, but will require drilling another set of holes. I'm glad I asked. Think I'll mover it closer to the keel as shown in your picture and see what happens. I also have a single 300 HP Suzuki; just love it. [I hope] to get reading when on plane, but at 50 MPH, I'm glancing at the tachometer and the GPS for speed and holding on for dear life. Would like to use a through-hull transducer, but don't really want to drill [large] holes through my hull. Has anyone [installed a through-hull SONAR transducer in a Boston Whaler 22-foot hull] with great success? Thanks for the information, been a great help.
TransAm	posted 05-29-2009 11:21 AM ET (US) I am considering a thru-hull transducer for a couple of reasons as I need to replace my fishfinder/sonar unit. The first, as has been mentioned, is the ability of the unit to transmit data while underway at higher speeds. The second is that a thru-hull transducer is not subject to being knocked around and damaged sitting exposed on the transom. Having just replaced both stern thru-hull brass drains, I am much less concerned about drilling another hole in the hull because of the technique I used. A picture is worth a thousand words, so I'll try and post a diagram. I have seen this technique before, perhaps here of on another site. I did 2 of these in about an hour and a half including the removal of the old brass tubes. http://s299.photobucket.com/albums/mm314/77SETransAm/?action=view& current=Thru-hull.jpg The addition of Epoxy completely seals the hull and prevents water from entering the foam. Simply slide the thru-hull in the bottom (you will need a fairing block which often comes with the set-up), seal it with some 5200 and you are good to go.
GTL	posted 05-29-2009 03:16 PM ET (US) TransAm: Know you are local, (I live in Davidsonville,MD) so I'd like to see when you put in the Through Hull Transducer ....Please take lots of picture, I like to do that my self, just a little adverse to drilling holes in the hull. Right how, I'm going to move my transducer to a similar position that JimH showed in his picture ... I'll post back with the results Thanks
TransAm	posted 05-29-2009 03:24 PM ET (US) I drive through Davidsonville almost every week in the summer down to my summer house in Beverly Beach. I'll keep you posted.
jimh	posted 05-29-2009 08:33 PM ET (US) ASIDE: If you need help with authoring on this forum, please see the information in the pages linked under "author help." A hyperlink appears on every page.
GTL	posted 05-31-2009 04:54 AM ET (US) Well, moved my transducer to the approximate location shown in JimH's pictures. Ran the boat yesterday and the depth finder held bottom the whole time, even at speeds in access of 40 MPH. At higher speed, it lost the ability to find fish, but knew the water depth. Thus I wasn't concerned about running aground. Thanks for the help. Now to fill the old mounting holes with gel coat.
jimh	posted 05-31-2009 10:45 AM ET (US) Thanks for the follow-up to let us know the outcome. It sounds like you have moved the SONAR transducer to a good location on the Whaler Drive.
Slippery Eel	posted 06-02-2009 10:36 AM ET (US) I installed a new Raymarine unit on my 22 Revenge with Whaler Drive this spring. I have either the P58 or P88 Airmar transducer. The instructions called for it to be mounted within 3" of the prop diamater. I followed this and found it works fairly well at all speeds. I still lose the signal occasionally on a sharp turn or in reverse due to prop wash.