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Transducer mounting

Discussion in 'Boats and Motors' started by DrChip, Mar 18, 2005.

  1. Thanks to everyone who responded to a previous post a few weeks ago about mounting a GPS module.

    Now I'm getting ready to transom mount the transducer for my depth finder. I've got an aluminum Tracker boat that already has three bolt holes (original Humminbird flasher, now deceased) and three screw holes (pickup for my speedometer) in the transom. I was really hoping to not drill more holes, but the holes for the Humminbird don't match up to the mounting bracket I have for the Eagle depthfinder/GPS.

    The mounting bracket includes two stainless screws and the manual says I need a #29 drill bit (which is like .164 inches) to drill the holes to match these screws. That bit seems non-standard -- I can't find one either at Lowes or my local specialty woodworking store. I'm told I'll probably have to special order it.

    Am I missing something, or can I just go buy two new stainless screws that will fit the hole of a standard drill bit (1/8" would be close) and go with that? Is there some other special bit I'll need because this is aluminum and it will be under the water line?

    Is there another alternative? For instance, could I avoid having to drill holes by mounting the bracket with epoxy or super glue or something? (I don't mean a thru hull mount, I mean glueing the bracket to the transom.) I would really prefer not to have more holes in the transom of this nearly 20-year old boat...

    Thanks in advance for any advice.

  2. Reel Man

    Reel Man Member

    If you want to order one you can do so online at the part number is 2912A203 it will cost $1.24 plus shipping.

  3. Dr.chip, I would recomend getting one of those transom mounting plates. This way you don't have to keep puting holes in your boat every time you change fish finders. You could mount two or three on it at a time if you want.I put one on mine and I'm glad I did . You can get them at Cabelas,Pro Bass ,West Marine. I hope this helps.....JIM
    Reel Man , My wife works for McMaster . They got everything......
  4. Thanks again -- OGF is a great place with great advice! Went to Sears this AM to see if they had the bit, but no luck -- the guy had never heard of a numbered bit (neither had most of the other folks I talked to yesterday). So, I ordered it from mcmaster

    Of course, after doing that I checked out the mounting plate Jim suggested -- and decided that was a smart idea too, especially if I add a speed paddle wheel to my depth finder. So, I may not have a use for the #29 bit after all, but maybe will have to get a different bit to install the mounting plate. Jim, did you have to get a special bit to mount yours to your hull? (I got the 8x12 mounting plate from Cabelas.)

  5. Drchip, you mean the 4 by 12 don't you? Thats the same one I got. Make sure you put sealer and reinstall the old screws. That plate just uses standard screws and drill bits. You should have no trouble installing it at all....JIM
  6. I'm cheaper than all of you guys. #29 bit no way.

    I'm using a piece of treated lumber attached with drywall screws.

    After that has too many holes in it, I'll just saw up another piece and replace the existing one.

  7. If you have a GPS you won't need a speedometer whirlygig. It will just pick up seaweed etc.

  8. One more consideration about using a transducer mounting plate or a portable transducer bracket.

    I know we are only talking about 1 inch or less mounting behind (aft) of the transom but one big item that degrades the fish finder signal is turbulant flow over the signaling device, and that little gap could be an issue.

    So be sure to provide for this.


    MAINAH Little Member

    Drchip, A #29 drill bit is .011 inches bigger than an 1/8 inch. I have a set of bits from HUOT TOOLS. it comes in an index from #1 to #60, #1 being .228 inches and #60 being .040 inches. I believe they are numbered this way for tapping, there is a coralating tap size given for each bit. Why I have these in my shop I dont know. Good luck hope this helps. MAINAH