Transom mount transducer converted to in hull (wet box) transducer

 Hi all, I have a TM185M 1KW transducer (transom mount) and at speeds over 10knts it's not worth looking at the screen other than for depth and at more than 20kt's it loses bottom altogether. I have moved it all over the place, had rooster tails, changed angles, skimmed it etc and haven't seen much more improvement.

At slow speeds it's awesome, great definition of the bottom and for marking fish. 

So I have decided to try and mount it inside the hull and shoot it through the fibreglass. The boat is a 2003 cruise craft 625 outsider and talking with cruise craft the bilge area is all solid fibreglass so it should/might work.

So any advice ? Has anyone done this with a 1kw transom mount ? 

When I purchased the transducer it came with a warning about mounting it internally due to heat, but other than the little warning sticker I haven't been able to find much on the web. My plan is to make a wetbox setup, and I assume that this would be sufficient to manage the heat issue ?

Am I wasting my time, should I just sell the TM185M and buy a through hull transducer and drill a bloody big hole in the boat ? 

 


Tim's picture

Posts: 2441

Date Joined: 26/09/06

Chirp

Sat, 2021-02-27 12:23

As its chirp it will need the fluid of a wetbox so that will work.

My understanding was that chirp doesnt work very well in a wet box though. Shooting through the glass will cause issues with your readings apparently.

If you want the best reading at speed I would look at afairing block mount if you have the room to fit it. Smaller holes to drill through the hull too :)

 

Posts: 52

Date Joined: 09/01/12

 Thanks Tim, I tried to

Sun, 2021-02-28 15:05

 Thanks Tim, I tried to adjust the transom mount again and took it for a run on the river and it was worse... so I am going to give it a go putting it in the bilge. Costs me nothing so why not. 

will post results..

Tim's picture

Posts: 2441

Date Joined: 26/09/06

Test

Sun, 2021-02-28 15:57

If you test it in the bilge make sure there is some water in there. Chirp can run hot and burn out the transducer if they dont have the water for cooling

Posts: 784

Date Joined: 19/06/14

Airmar M260

Sun, 2021-02-28 18:08

 I've got one of these in my cat, shoots through the glass no worries. Nice bit of kit.

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Posts: 52

Date Joined: 09/01/12

 Ok thanks chaps I'll give it

Mon, 2021-03-01 09:44

 

Ok thanks chaps I'll give it a go as it costs me nothing, if it doesn't work then I might have to revert to a through hull, although I know that is no guarantee either. The fairing job looks a bit complicated for my boat. 

 

Anyway I got number one son to print me a box adjusted for deadrise on his 3d printer. I'll use some 291 Sika to stick it down for the trial and take the boat for a run when this weather passes. I am in two minds about sanding back the paint/speckle over the fiberglass for this trial. 

 

 

Posts: 52

Date Joined: 09/01/12

 Ok thanks chaps I'll give it

Mon, 2021-03-01 09:44

 

Ok thanks chaps I'll give it a go as it costs me nothing, if it doesn't work then I might have to revert to a through hull, although I know that is no guarantee either. The fairing job looks a bit complicated for my boat. 

 

Anyway I got number one son to print me a box adjusted for deadrise on his 3d printer. I'll use some 291 Sika to stick it down for the trial and take the boat for a run when this weather passes. I am in two minds about sanding back the paint/speckle over the fiberglass for this trial. 

 

 

Posts: 784

Date Joined: 19/06/14

No need to sand

Mon, 2021-03-01 13:02

Only sand if your surface isn't smooth ( no chunky glass bits ). Use distilled water in the box.  

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 My wife understands why I clean my rods n reels in the shower....

 

Posts: 52

Date Joined: 09/01/12

 Well, I went out on Saturday

Sun, 2021-03-07 10:24

 Well, I went out on Saturday and as you guys know it wasn't as nice as forecast with a WSW breeze kicking up some short chop. Good weather for testing a homemade wetbox transduer set up.

 

I have some images that show how well it worked, (I used to be able to upload images on this forum but can't see that function here anymore ? ) but basically at rest or <10knts in yesterdays contitions it was a perfect image. I only got up to 27knts due to chop, and was flying off the top of some waves, but the sounder never lost bottom readings, I could continue to see bottom contours also. At that speed no chance to spot fish, but it's miles better than having the transom mount. 

In summary it was a great move to put it inside the hull and I have seen only an improvement on the image quality including spotting fish.

Today I will  be filling in the holes in the transom and the prototype is set to stay in place. :) 

Posts: 784

Date Joined: 19/06/14

Nice work.

Sun, 2021-03-07 21:12

It's in the best place by the sounds of things. No more worries of some goon cutting it off the back of your boat anymore!. 

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 My wife understands why I clean my rods n reels in the shower....