Transducer Placement

[flood tide]

Hello all. I'm having a problem with my transducer picking up the bottom. I had a thru hull installed at a very reputable boat yard within the past 2 weeks. Its an airmar b117 600w connected to a garmin 740s unit. I've been running the boat and playing with various settings constantly since then. I still lose contact with the bottom every time I get the boat up to speed, on plane, and in reverse. I decided to go with the thru hull specifically to avoid this problem. The boat is a 1985 Seaway 19' semi displacement hull. It has a small keel that runs 2/3 the way under the hull and a soft chine. The transducer was installed near the port stern.

After talking to some folks at airmar they suggested that the transducer was placed improperly. Their instructions state it should be placed starboard side of the engine whereas the propeller moves in a downward motion instead of upward at the port side.

I havent paid the bill for the installation yet. Do you think it would be wise to have them cut another hole in my hull and move the transducer? Could this be an issue with the shape of the hull rather than placement location?

Has anyone ever owned one of these boats or a similar hull and put a thru hull in theirs? were you able to hold the bottom at speed? Where was yours placed?


Thank you for your help

Steve

 

[GoodChance]

Couple of things could be wrong. First of all, always mount the transducer on the starboard side of the centerline. Second, all downeast boats/semi-displacement hulls should have their transducers mounted in the forward 1/3 of the hull, where the hull is deepest. Planing hulls get their transducers mounted in the stern. Not true for downeast hulls. Same as sailboats. I'm not certain of the hull shape of a 19 Seaway though.

 

[shoefish]

Flood Tide, I have a 21' Seaway and put in a very similar set up (Garmin 740s and through hull). I installed it on the starboard stern, about half way between the centerline and the starboard edge. I run up to 30kts and hold bottom in 300' of water without a problem. If it was me I'd have them move it- it would drive me nuts not to be able to read bottom while I was running.

 

[captainlarry84]

The B117 is a very user friendly transducer. It is flush mounted with no hangdown and it should work like a dream.
For starters none will work when you reverse because of the propeller pushing the water across the area of the bottom where the transducer is located.
In addition the B117 has no tilt feather and requires a fairing block unless it is mounted on a totally flat surface of the hull.
You need to show us a picture of the install. If there are and thru hulls, pick ups or chine rises in or around the transducer it will not perform.
I have the B117 on my 600 watt Sitex at 22 knots I read great bottom as should you.
I assume at rest the unit reads well?
I do not think port or starboard makes a difference because all of the propeller wash is well behind the transducer.
If the transducer is mount after the keel it is very possible that when the water exits from around the keel it is pick up some air and causing a water disturbance on the flat area where your transducer is located.
I have install may transducers on keeled boats. I like the transducer midship about 1 foot away from the keel area.
Lastly nothing I mean nothing and be in front of that transducer. Send a picture.
Lastly filling a transducer hole is not a big job, it is just unnecessary work.
My B117 is mounted on the port side at amidships.
I think you have a very good lead with Shoefish. I would get of picture of his placement & go accordingly.

 

[flood tide]

Thank you all for the helpful responses. I still have the boat in the water. I'll try to get some pictures up soon as I take the boat out for the winter. Happy thanksgiving to everyone.

 

[flood tide]

Hey Shoefish I was wondering, when you get a chance, If you could let me know how far infront of the transom your through hull sits. Thanks again.

 

[shoefish]

Absolutely. Sorry for not responding sooner- I've been in a triptophan coma for a couple of days. I'll take some pics tomorrow and will post them up.

 

[shoefish]

Here is a pic of my through hull placement. I took a few others too if you want to see them. Like I said, this has worked well for me with no issues. Hope it helps!
Shoe