Go Back  The Hull Truth - Boating and Fishing Forum > BOATING FORUMS > Marine Electronics Forum
Reload this Page >

Location in Transom to Mount Transducer of a FishFinder‏

Notices
Marine Electronics Forum

Location in Transom to Mount Transducer of a FishFinder‏

Old 07-02-2014, 07:04 PM
  #1  
Junior Member
Thread Starter
 
Join Date: Jul 2014
Location: Northern New Jersey
Posts: 9
Default Location in Transom to Mount Transducer of a FishFinder‏

I am a bit confused of the proper location to mount the transducer of a Humminbird SideImaging fishfinder. The transducer is a skimmer that is mounted at the bottom edge of the transom. According to the installation instruction, the transducer needs to keep a minimum 15" distance away from the propeller. I am wondering how this 15" distance is measured in my small 18-ft boat that has an outboard motor:

Is this measured between the outside edge of the propeller and the transducer in a diagonal line? If this is the case, the fact that the boat has an outboard (or I/O) makes a big difference. The reason is that the propeller of an outboard is far away from the transom. That will make positioning the transducer an easy job.

Is this measured between the center line of the boat hull and the transducer in a horizontal line (taking into account of the radius of the propeller)? If this is the case, the fact that the boar has an outboard doesn't make any difference. The distance is calculated from the center line anyway. And this will make positioning the transducer a far more difficult job because 15" distance will put the transducer right behind a strake in the bottom of the boat hull. Moving it a bit farther away will put the transducer right at the path of a support bunk of the trailer. The only way is to mount it quite far away that it will be near the chine of the boat hull (like 1-ft to the chine) -- that doesn't seem right. The other way is to move it closer (like 10" instead of 15"); but that will be against the recommended minimum distance.

I have contacted Humminbird tech support. He said that the minimum distance is measured from the center line of the boat (taking into the account of the radius of the propeller). This means I have a PROBLEM.

My questions are:

1. Please confirm that the minimum distance is indeed from the center line of the boat to the transducer.

2. Does anyone use a skimmer type transducer with a Humminbird SideImaging fishfinder? How far is your transducer from the center line? What is the result?

3. What will be the problem if I install the transducer close to the chine of the boat? Honestly I really don't want to do this. The reason is that the bottom edge of the transom is curving upward and outward. The further outward the bottom edge is, the softer and rounder the edge is. In order to mount a transducer in that area, I will have to add quite some material to turn the round edge into a sharp edge. Therefore, I prefer to mount the transducer closer to the center line.

4. If I decide to mount the transducer closer to the center line and below the 15" minimum, what the result will be. Will this mean that I need to run the boat at slow speed in order to use the fishfinder.

5. Does this mean that I need to replace it with a "thru hull" transducer? Does the 15" minimum still apply to "thru hull" transducer?

Please let me know what you think. Thanks in advance.

Jay Chan
jaykchan is offline  
Old 07-03-2014, 05:53 PM
  #2  
Junior Member
Thread Starter
 
Join Date: Jul 2014
Location: Northern New Jersey
Posts: 9
Default

I have found the answers of some of my questions:

1. Yes, the 15" minimum distance is indeed from the outside edge of the propeller to the transducer in a horizontal line. I was confused because the picture in the installation instruction is missing the part that shows the exact location of the 15" distance. The new installation instruction available in their web site has the missing info. This also means that I have a problem finding a location in the transom to mount the transducer.

Based on this new info, this makes the transducer right at the path of the bunk of the trailer (not at the path of a strake as mentioned in my original post). This means I have to move the transducer outside the path of the bunk.

3. What complicates thing is that the area outside the path of the bunk has a very steep transom angle. And the transom is actually tapering outward. This means if I need to build up that area, I will have to deal with a compound angle. I probably will have to do this. Oh well...

Jay Chan
Attached Images    
jaykchan is offline  
Old 07-03-2014, 06:21 PM
  #3  
Senior Member
 
Join Date: Aug 2006
Location: San Diego
Posts: 3,324
Default

Not infrequently, TM placement is problematic, and requires experimentation. From what I see in your pictures, you may have a tough time of it, so whatever you do, figure out a way to test your location without drilling holes into your transom. There are previous threads on this I believe. As a matter of fact, once you've found the best spot, I still wouldn't drill any holes into your transom, but rather utilize one of the commercially available stern saver pads (or make your own). TM placement is an art, not a science, so I wouldn't let an inch or two variance from the instructions get in your way.

Or ... you could use a thru-hull transducer and be done with it.
Pez Vela is offline  
Old 07-04-2014, 02:27 AM
  #4  
Senior Member
 
Join Date: Mar 2013
Location: South Carolina
Posts: 1,543
Default

I had a similar problem with a 998 that I had. To test transducer locations, I used a 8" c-clamp and clamped a 2x4 to the transom angling down from the splash well. I then mounted the transducer to the board. I could then run the boat at different speeds up to wide open throttle to test the location. If a location did not work accordingly, I put the boat on the trailer and moved the board and transducer around to test another location. I since have gone to a thru-hull transducer.
FishLife is offline  
Old 07-04-2014, 05:39 AM
  #5  
Admirals Club Admiral's Club Member
 
Join Date: Nov 2011
Location: sarasota
Posts: 3,611
Default

See if it can be mounted in the bilge, mine shoots right through the hull, no drilling, never gets knocked off, while trail earring etc..did lose the temp function
gumpire is offline  
Old 07-04-2014, 07:22 AM
  #6  
Junior Member
Thread Starter
 
Join Date: Jul 2014
Location: Northern New Jersey
Posts: 9
Default

Thanks for all the useful advises that I have received. I appreciate that.

In my last post, I said I might install the transducer far away from the center line of the boat and near the chine. I have a second thought. I doubt that the side-imaging function will work in this configuration. The reason is that the transducer would be mounted higher than if it was mounted near the center line. There might be a chance that the lower unit of the outboard or the supporting structure for the outboard might block the side-imaging signal, or may be not, hard to say. Add adding to the fact that the spot is too steep an angle, and need some work to build up in that spot. If I am not reasonably sure that the spot will work, I will not want to drill into it.

Seem like so many things are iffy. In theory, I need to do what forum members Pez Vela and FishLife have suggested. That is to temporarily mount the transducer in a piece of wood and clamp it on the transom, and to try different locations until I find the right spot. Unfortunately, the bottom edge of the transom in my boat is too curvy to mount the wood securely. Moreover, I cannot figure out any way to mount a wood to test the spot near the chine (the big buck head on top of that spot gets in the way of clamping a piece of wood).

Seem like I need to try what gumpire has done - using a In-Hull transducer (inside-the-hull/shoot-through-the-hull). The boat manufacture told me that the aft bottom of the boat is made from a single layer of fiberglass. Therefore, I may be able to use the In-Hull transducer. And I don't need to drill any hole. And Humminbird seems to have a program to swap the skimmer type transducer with an In-Hull transducer for free. Seem like there are a lot of up-sides. The only downside is that some signal strength will be lost. Luckily, my boat is a "bay boat", and I am supposed to stay in shallow water anyway. The possibility that the In-Hull transducer cannot give me a good signal in deep water doesn't really matter to me. If In-Hull transducer doesn't work for me, the next step will be a "Thru Hull" transducer that requires me to drill a hole in the bottom of the hull.

Thanks again for sharing your experiences and offering your suggestions.

Jay Chan
jaykchan is offline  
Old 07-06-2014, 06:44 AM
  #7  
Junior Member
Thread Starter
 
Join Date: Jul 2014
Location: Northern New Jersey
Posts: 9
Default

I need to eat my words. In my last post, I said I would not try using the transom mount transducer, and I probably would use a "In-Hull" transducer. Unfortunately, HumminBird doesn't have a In-Hull transducer that can do side-imaging. Their In-Hull transducer is to get water depth and looking for fishing when the boat is in high speed. It is not for looking for structures on the sides of the boat -- no side-imaging.

I decide not to try a thru-hull transducer because the Humminbird thru-hull transducer is kind of sticking out, and I am afraid of it being hit by submerged wood log. Moreover, there is no other thru-hull fitting in the bottom of the hull currently; I don't want to start drilling holes now. Finally that side-imaging thru-hull transducer is expensive.

Seem like I will have to try a combination approach using both the skimmer type side-imaging transducer for slow speed, and a In-Hull transducer for high speed (no side-imaging).

This means I am back to deal with the issue of how to mount the skimmer-type transducer in the transom. I think I will build up the transom area 5" to 10" outside the propeller outside edge to make sure that area is flat (instead of curvy and tapered), and then mount a piece of starboard kind of material over the built-up area, temporarily mount the transducer onto the starboard. and start experimenting with various mounting location.

Thanks for listening.

Jay Chan
jaykchan is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are Off


Thread Tools
Search this Thread