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  1. #1
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    P79 HIGH SPEED IN HULL TRANSDUCER

    I am installing the Axiom 9 and 12 on the boat. The 9 will be in the back hooked to the RV100 and the P79 in hull transducer will also be siliconed in the hull.

    Question about the P79. Manual indicates using the angle indicator and base that come in the package. Is that needed on a bass boat that falls in line or below the 0-5 degree angle mark?
    If it is not needed....does that mean I just need to silicone the face of the puck straight to the hull? (Of course after cleaning and following other protocols).
    I'm just worried about not following these directions. But it doesn't look like it is needed and the angle indicator and base look like they could through the readings off.

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    #2
    Most bass guy just properly clean and scuff the face of the puck. Affix directly to the hull. You can use the reservoir with antifreeze if you want, but that step is usually skipped in applications like yours.

  3. BBC SPONSOR BassFishin Electronics's Avatar
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    #3
    I've had issues with installing a transducer with silicone in the past. I would hope highly recommend using epoxy

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    #4
    I am open to either. Only reason I was going with silicone is because that is what the manual suggested. What kind of issues would I run into?

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    #5
    I would agree with using epoxy. Mix it slow so you don't have any air bubbles and get good contact.

  6. Honda / Raymarine Moderator Hickory Legend's Avatar
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    #6
    Yep on the epoxy!!

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    #7
    what kind of epoxy? Does it have to be a certain kind?

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    #8
    I don't have a recommended brand - just make sure it's a slow cure.
    1. Slow cure allows more time for any air bubbles to go away
    2. Some fast cure expoxies heat up and can damage transdcuers.

  9. Honda / Raymarine Moderator Hickory Legend's Avatar
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    #9
    I have used 60 min, if it’s too long it can run out from under the transducer. You also can form a little mold around it to hold in the epoxy modeling clay or cardboard, something a little bigger than the transducer.

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    #10
    Have any of you guys actually installed a P79?!

    Install it exactly as the directions indicate. Silicone the ring to the hull. Let it dry. Then fill with the RV antifreeze and install the puck. The whole point of the antifreeze is to get rid of the variability and possibility of air bubbles that silicone and epoxy cause under the puck.

    Do not skip the ring and silicone the puck to the hull. I have installed these on multiple boats and will never go back to a puck that is epoxied to the hull.

    That less than 5 degree variability will be absorbed by you sitting in the driver's seat and an unbalanced load.

    A tip to get the recommended amount of antifreeze is to buy a medicine syringe at the drug store and use that to squirt the antifreeze in.
    2015 Yellowfin 21 with 2014 Yamaha SHO 250

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    #11
    Wouldn't be giving advice if I hadn't.

    Prep hull first. Sand it down, clean area with alcohol, build a little dam with silicone (let cure for a couple hours), then mix slow cure 2 part epoxy, mix slow to not create air bubbles in epoxy and pour in reservoir. Put xducer down into epoxy twist around a little to make sure there is no air pockets, put a weight on it (like a big sinker or a small sandbag) to keep pressure while it cures. Been installing this way for 30+ years.


    Face of that transducer is angled. Just put it so it is as flat as possible. 20 degrees is top dead rise. Also, you can take a grinder (dremmel, etc) and smooth a flatter area out if needed. I dont like over 10 degrees with a straight epoxy job, again, less dead rise is better and easier to install and keep in place during epoxy set up.

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    #12
    I'm not sure but I think Yellowfin has a 24 degree deadrise. Above the 10 degree max - different hull / application than a bass boat.

    0-10 - OK direct ducer to hull
    10-22 - use the cup

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    #13
    Quote Originally Posted by Jig34 View Post
    I'm not sure but I think Yellowfin has a 24 degree deadrise. Above the 10 degree max - different hull / application than a bass boat.

    0-10 - OK direct ducer to hull
    10-22 - use the cup
    12 degree. It's a 21'10" stepped hull flats boat with a pad vee. Same dead rise as a ton of bass boats if the transducer is not mounted on the pad. Also, you are missing the main advantage to the P79 by glueing it to the hull which is using the same liquid transmission medium that multi thousand dollar commercial transducers use.

    Also, if you ever wanted to upgrade the the P75M chirp transducer, it is plug and play in the P79 cup. Twist one out then twist the new one in. No messy epoxy or silicone removal needed.
    2015 Yellowfin 21 with 2014 Yamaha SHO 250

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    #14
    Quote Originally Posted by Jig34 View Post
    Wouldn't be giving advice if I hadn't.

    Prep hull first. Sand it down, clean area with alcohol, build a little dam with silicone (let cure for a couple hours), then mix slow cure 2 part epoxy, mix slow to not create air bubbles in epoxy and pour in reservoir. Put xducer down into epoxy twist around a little to make sure there is no air pockets, put a weight on it (like a big sinker or a small sandbag) to keep pressure while it cures. Been installing this way for 30+ years.


    Face of that transducer is angled. Just put it so it is as flat as possible. 20 degrees is top dead rise. Also, you can take a grinder (dremmel, etc) and smooth a flatter area out if needed. I dont like over 10 degrees with a straight epoxy job, again, less dead rise is better and easier to install and keep in place during epoxy set up.
    I'm trying to find where in the P79 installation instructions Airmar recommends this method.

    Here they are.
    http://www.airmartechnology.com/uplo.../17-217-01.pdf
    2015 Yellowfin 21 with 2014 Yamaha SHO 250

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    #15
    I doubt you see it printed anywhere.

    P74 is a trolling motor / in-hull transducer
    P79 is essentially a P74 with a reservoir for deadrise up to 22 degrees.

    If if you want to use the reservoir with anti-freeze that's exactly what the instructions show. For boats with a deadrise less than 10 degrees, guys have been using epoxy direct for 30+ years.

  16. Honda / Raymarine Moderator Hickory Legend's Avatar
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    #16
    I haven't done a P79 or any in a large salt water boat, But have installed transducers in many bass boats.

    In a bass boat you don't need that fancy ring and measurements. Just clean a spot free of dirt and oil. back on the pad by the drain plug. Mix up the epoxy and stick that sucker to the hull.

    The ring and antifreeze is for v bottom boats where you don't have a flat spot.

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    #17
    I just can't understand the recommendations to go against the factory installation method when the Airmar method takes exactly the same amount of work, has less room for error, and will probably give a better signal. Do whatever you want. I'll stick to what Airmar suggests.
    2015 Yellowfin 21 with 2014 Yamaha SHO 250

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    #18
    Quote Originally Posted by Hickory Legend View Post
    I haven't done a P79 or any in a large salt water boat, But have installed transducers in many bass boats.
    This is a Yellowfin 21. As close to a bass boat you can get with a center console.
    2015 Yellowfin 21 with 2014 Yamaha SHO 250

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    #19
    Quote Originally Posted by Marshfly View Post
    Have any of you guys actually installed a P79?!

    Install it exactly as the directions indicate. Silicone the ring to the hull. Let it dry. Then fill with the RV antifreeze and install the puck. The whole point of the antifreeze is to get rid of the variability and possibility of air bubbles that silicone and epoxy cause under the puck.

    Do not skip the ring and silicone the puck to the hull. I have installed these on multiple boats and will never go back to a puck that is epoxied to the hull.

    That less than 5 degree variability will be absorbed by you sitting in the driver's seat and an unbalanced load.

    A tip to get the recommended amount of antifreeze is to buy a medicine syringe at the drug store and use that to squirt the antifreeze in.
    a had a gt15, which is a copy of the p79 installed in my stratos. We installed exactly as you say. Silicone to hull. no epoxy needed. the antifreeze also serves to cool the transducer as it was a true chirp transducer. it also came with different angled cups to fit any hull deadrise angle between 0 and 25 degrees

    1)test for best install location
    2)sand the tested location
    3)apply marine grade adhesive to the bottom of the tank
    4)place the tank in the boat hull
    5)when the adhesive is dry insert the o ring
    6)fill the tank with rv/marine antifreeze or mineral oil
    7)insert the transducer
    8) secure transducer to tank
    Last edited by TroyBoy30; 09-28-2017 at 06:55 AM.

  20. Honda / Raymarine Moderator Hickory Legend's Avatar
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    #20
    If it was a Chirp transducer, I would mount it that way because of the heat, being the P79 isn’t I would mount it the way it’s been done in bass boats since they’ve been sticking them in hull.

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