Transducer question

[copacabana]

I just bought a new Garmin 90 fishfinder to replace the old depth meter in my boat (35ft). The problem is the Garmin 90 comes with one of those transom-mount transducers that are supposed to be mounted externally. The fellow in the store told me that it could be mounted inside the hull and it would work fine. Is this true? Has anyone here ever done this? Any advice on how to do this? Thanks in advance!

[sailingdog]

Yes, it can be mounted internally, provided you have a solid fiberglass hull with no core. I generally recommend glassing a piece of 4" schedule 40 PVC pipe to the hull and putting a clean out fitting on it and then mounting the transducer to the fitting and filling the pipe with mineral oil.

You will need to find a good spot on the hull to mount it, and can do this by hooking up the transducer and placing it on a plastic bag full of water and moving it until you find a spot it reads well in.

[copacabana]

That's great news, thanks. Now, any suggestions on where to mount it? I've got a full keel with a cutaway forefoot. I was thinking just ahead of the keel.

[BarryL]

Hi,

As you wrote, a good place to mount it is in front of the keel. This way you can see ahead of time that you are going to run aground

Also, you can temporarily stick the transducer to the hull with toilet bowl wax. Spread some on the hull and then squish the transducer into it. The transducer won't move and will provide good readings.

Good luck,
Barry

[QuickMick]

i just followed sailingdogs advice with my new hummingbird, and she works like a charm

[copacabana]

I just thought I'd update this thread with the final results of my transducer installation and a few lessons learned.

First of all, thanks for the advice. SD, the idea of using a ziplock bag full of water to take a test depth reading didn't work- I couldn't get a reading through it. I just made a little well with modeling putty (the kids kind) and filled it with water. After finding a good place to install the 2 transducers (fishfinder and GPS/fishfinder combo), I cleaned the area carefully and put a blob of silicone on the hull. Then I smoothed it with my finger, taking out any air bubbles, but leaving a thick layer of silicone. Then I carefully pushed the transducer into the silicone, squeezing out any bubbles. I am able to get a good depth reading and bottom image and if I ever decide to remove or move the transducer, it'll be a snap (something not easy to do if you use epoxy resin to bed the transducer). For added caution I cut a piece of PVC pipe to put around the transducer to protect it from getting banged out of place. I thought it might be useful to share this experience to provide another method for installing this kind of transducer besides using epoxy resin or making a PVC pipe 'pool' filled with liquid.