Mine did not have any adapter, and I thought it was just a test install. I wiped the location down with lacquer thinner and scuffed it a little. Put some silicone down and pushed the transducer into it.

So, The whole face of the transducer is imbedded into the silicone...and it essentially shoots through it? Now that I think about it, it makes sense that a little (or a lot) of silicone would not be any harder to shoot through than the fiberglass of the boat hull.
Thanks!

Yes
i guess probably 1/8 - 1/4”

:-)

Any old Formula (1988 311 SR1) people have a recommended route for the transducer cable...looks like getting under the gloss black dash (near the compass) is a tough act.

Thickness doesn't matter because it will all squeeze out anyway whether thats 1/8inch or 1/2 inch. Just make sure you have thick enough to completely fill all the space between puck and hull and a little extra to make sure. Just a tip - either make a little mound in the middle of the sealant so no air bubbles get trapped, or maybe push the puck in at a slight angle to get all the air out. Push the puck all the way until it touches the hull.

Get tips! I'm using a 20 degree adapter for my 24 degree deadrise and it is supposed to be filled with antifreeze...so I will make sure no voids/bubbles. Any idea how a bubble manifests itself in the transducer output signal/representation...like a black hole???