Mounting a transducer completely inside hull

[mwe-maxxowner]

I just purchased a Lowrance Mark 4 depth finder/GPS combo. I was researching mounting the transducer, and came across the possibility of mounting one inside the hull. How much does this affect the accuracy of depth readings? I don't fish, so I don't care about the accuracy over 5' or so. I just need to be able to tell whether the water is deep enough to safely drive around in and pull people during various watersports.

 

[wrench 3]

My last boat had one mounted inside the hull and it worked great. However it had a factory mounting spot that was horizontal. Also you will need a good seal to the hull with no air gaps.

 

[mwe-maxxowner]

Thank you much! As I understand it, the transducer needs to be parallel to the surface of the water to be accurate? my bilge is sloped on each side and comes to a"v", but the angle is very shallow. Even at a shallow angle, will it make it inaccurate? Or, what if I mount it in the center of the "v", and fill in the space below it with fiberglass resin, 5200, bondo, etc so there is not an air pocket between the transducer and the hull?

 

[GA_Boater]

Honestly, mxe, I don't know if being parallel to the water really matters. If you epoxy the xducer perfectly level when the boat is at rest, all the references change as soon as you get on plane, turn on the water or even rock due to wake and waves. In the bilge, as close to the keel line as possible and no air pockets in the epoxy bed should be fine.

 

[mwe-maxxowner]

Ah heck. I might just mount it outside the boat. I did completely gut and resto the boat, including a large gash from the circular saw. I shouldn't be afraid to drill into the hull haha. The Mark 4 description reads that it includes an "83/200 high speed low profile transom mount Skimmer transducer". I believe I should be able to epoxy it to the transom, or fix a plate to the transom, and attach the transducer to the plate. Sorry guys, this is entirely new territory to me. I just know I'm tired of being so uneasy in new water until I've roamed around a bit to assure myself it is all safe. I'm thinking a transom mount would make the transducer pretty safe on the outside of the hull, and I don't think it would require me to saw a hole in the hull. To boot, this would allow me to retain the water temperature feature (though my hand works pretty well to tell me what the water feels like).

Are there any tips, other than make it as close to the keel as possible, to help it work well at speed?

 

[mwe-maxxowner]

Sorry. It said that it didn't post the first time .

 

[GA_Boater]

mxe - Are you thinking you have to put a hole in the hull for an inside mount? No hole needed. Yeah, temp won't work on an inside mount. For a transom mount two or three small screw mounting holes need to be drilled and depending on your transom you may need a larger hole for cable routing. If you won't be using it for finding fish, you can mount it almost anywhere, except it must be in the water on plane to read depth. The installation booklet explains both the inside and transom options well, my Lowrance did.

 

[HalfFish5087]

No Title

Just installed the Mark 4 without the GPS. I had a depth sounder in the boat but I wanted to be able to see a profile view so I could see if I was getting shallower or deeper, etc.
From the directions given in the manual, you want half of the transducer in the flow of water at all times and have it at least 12 inches away from the prop to avoid cavitation.
Depth sounding is working well, but profile view gets a little sketchy when I pass about 30 mph. Here is a pic.

 

[mwe-maxxowner]

mxe - Are you thinking you have to put a hole in the hull for an inside mount? No hole needed. Yeah, temp won't work on an inside mount. For a transom mount two or three small screw mounting holes need to be drilled and depending on your transom you may need a larger hole for cable routing. If you won't be using it for finding fish, you can mount it almost anywhere, except it must be in the water on plane to read depth. The installation booklet explains both the inside and transom options well, my Lowrance did.

Not exactly. I read some generic instructions online where it was necessary to drill a hole in the hull. In these cases the transducer was inside the hull , through the hull, and extending to the outside. And yeah I know the temp reading won't work inside . It'll tell me the temp of any bilge water though! Thanks to each of you! I think I will either mount inside the bilge over an epoxy bed, or on a mounting plate secured to the transom with epoxy. I think right beside the drain plug as close to center and bottom as possible should be at least 12" away from the prop. Maybe stand the best chance of being clear of any bubbles while underway.

 

[Jesterarts]

I know this thread hasn't been updated in a while, but did you ever mount the transducer and how did you go?

I have a Mark-4 on it's way and I want to install it in my 1996 Searay 210. I've been reading up about mounting it inside the hull, but is seems that this can cause a significant reduction in sensitivity, in particular with the HDI mode.

Let me know how you went.

Cheers,

 

[bruceb58]

You are going to want to start a new thread. The OP hasn't been here since last June.