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Author Topic:   Transducer Placement on 1999 Dauntless

masbama posted 02-18-2008 09:32 PM ET (US)
I removed my transom mounted transducer because of the back splashing rooster tail and ordered a 'shoot through the hull' kind from Humminbird but I can't get a reading yet. (Hull may be too thick.) Has anyone had any success with a transducer that shoots through the hull or transom mounted that doesn't back splash all over the motor and stern? Brand, make, model?
jimh posted 02-18-2008 11:14 PM ET (US)
Generally you cannot use a SONAR transducer that tries to shoot through the hull on a Boston Whaler boat because of the Unibond hull construction. I do not recall a single report of success with that technique. There are a few models in which Boston Whaler has provided a special area in the hull which contains a "putty box" section. The "putty box" is a section of laminate without the usual foam filler and laminate construction which is intended to facilitate the mounting of a through-hull transducer. In Boston Whaler hulls which do not have such a feature, it is just about universal that a transom mounted transducer is used.
I have had great success using the LOWRANCE Skimmer transducer. It does not throw much spray at all when you have the mounting position correctly oriented.
Jefecinco posted 02-19-2008 09:18 AM ET (US)
Masbama,
IMO, any transom mounted xtucer will cause some degree of "rooster tailing". The Lowrance Skimmer xducer on my Dauntless throws some spray but not to a degree that I find objectionable and it does not throw water all over the transom and motor.
The installation manual for a Skimmer is available for download from the Lowrance site. The instructions are pretty decent but not all inclusive.
I recommend mounting a piece of Starboard lumber to the transome and them mounting the xducer to that. That way you can make changes to the mounting without drilling several holes in your transom. Although the manual tells you to mount the xducer level I've had perfect sounder performance with the xducer mounted a little bit off level. This allows a little less of the xducer to be in the water while on plane and, IMO, reduces xducer rooster tailing.
I've observed boats with the xducer mounted so that it is completely below the surface while on plane. This just creates unecessary drag, degrades sounder performance, and causes a spectacular rooster tail.
The great majority of boats use transom mounted xducers with great success. You can do the same but it requires a little bit of adjusting to get it right.
Butch
Lars Simonsen posted 02-19-2008 09:27 PM ET (US)
In my 1998 18' Dauntless, there is a section of the hull (it's in front of the bilge drain at the stern of the boat) that is, at least in part, not foam filled. It appears to be some sort of plastic (whaler board?) between the inner and outer fiberglass skin. I don't know why it's there, or whether it would work for a thru hull transducer. I just know it's there from having to replace a thru hull fitting for my livewell pump.
Looking at the wood locating diagram for my boat, it appears that the area there has a 3/8 thick 1" x 2" piece of phenol. The flat area that forms the "ceiling" of the tunnel is 1/2" plywood. Of course, it's above the tunnel in the hull, so it may not be ideal for a thru hull transducer, since at speed it's possible that this part of the hull is not in contact with water.
masbama posted 02-20-2008 09:28 PM ET (US)
Thanks!
I'll try to find the sweet spot and if I can't I'll try a Lowrance. The Humminbird transom transducer just doesn't cut it.
lurkynot posted 02-21-2008 07:24 AM ET (US)
Not positive but I recall when looking at the wood diagram for my 2001 Duantless there are 2 crosshatched areas just forward of the transom calling out an area suitable for a thru hull transducer application.

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Author	Topic: Transducer Placement on 1999 Dauntless
masbama	posted 02-18-2008 09:32 PM ET (US) I removed my transom mounted transducer because of the back splashing rooster tail and ordered a 'shoot through the hull' kind from Humminbird but I can't get a reading yet. (Hull may be too thick.) Has anyone had any success with a transducer that shoots through the hull or transom mounted that doesn't back splash all over the motor and stern? Brand, make, model?
jimh	posted 02-18-2008 11:14 PM ET (US) Generally you cannot use a SONAR transducer that tries to shoot through the hull on a Boston Whaler boat because of the Unibond hull construction. I do not recall a single report of success with that technique. There are a few models in which Boston Whaler has provided a special area in the hull which contains a "putty box" section. The "putty box" is a section of laminate without the usual foam filler and laminate construction which is intended to facilitate the mounting of a through-hull transducer. In Boston Whaler hulls which do not have such a feature, it is just about universal that a transom mounted transducer is used. I have had great success using the LOWRANCE Skimmer transducer. It does not throw much spray at all when you have the mounting position correctly oriented.
Jefecinco	posted 02-19-2008 09:18 AM ET (US) Masbama, IMO, any transom mounted xtucer will cause some degree of "rooster tailing". The Lowrance Skimmer xducer on my Dauntless throws some spray but not to a degree that I find objectionable and it does not throw water all over the transom and motor. The installation manual for a Skimmer is available for download from the Lowrance site. The instructions are pretty decent but not all inclusive. I recommend mounting a piece of Starboard lumber to the transome and them mounting the xducer to that. That way you can make changes to the mounting without drilling several holes in your transom. Although the manual tells you to mount the xducer level I've had perfect sounder performance with the xducer mounted a little bit off level. This allows a little less of the xducer to be in the water while on plane and, IMO, reduces xducer rooster tailing. I've observed boats with the xducer mounted so that it is completely below the surface while on plane. This just creates unecessary drag, degrades sounder performance, and causes a spectacular rooster tail. The great majority of boats use transom mounted xducers with great success. You can do the same but it requires a little bit of adjusting to get it right. Butch
Lars Simonsen	posted 02-19-2008 09:27 PM ET (US) In my 1998 18' Dauntless, there is a section of the hull (it's in front of the bilge drain at the stern of the boat) that is, at least in part, not foam filled. It appears to be some sort of plastic (whaler board?) between the inner and outer fiberglass skin. I don't know why it's there, or whether it would work for a thru hull transducer. I just know it's there from having to replace a thru hull fitting for my livewell pump. Looking at the wood locating diagram for my boat, it appears that the area there has a 3/8 thick 1" x 2" piece of phenol. The flat area that forms the "ceiling" of the tunnel is 1/2" plywood. Of course, it's above the tunnel in the hull, so it may not be ideal for a thru hull transducer, since at speed it's possible that this part of the hull is not in contact with water.
masbama	posted 02-20-2008 09:28 PM ET (US) Thanks! I'll try to find the sweet spot and if I can't I'll try a Lowrance. The Humminbird transom transducer just doesn't cut it.
lurkynot	posted 02-21-2008 07:24 AM ET (US) Not positive but I recall when looking at the wood diagram for my 2001 Duantless there are 2 crosshatched areas just forward of the transom calling out an area suitable for a thru hull transducer application.