This looks like it could get more involved than I want to get. Have you done it? If so, I am sure there is a story behind the install, please tell it to me.

Installed a handful
My BHM has an Airmar b260 the blue fairing block is huge (2ft long)
Location for the install is key.
Then you have to figure the dead rise angle, mine was 5 degrees. Being a downeast boat 5 degrees is not much, a planing hull will be more.
Mounted it in a tilted fence band saw for the cut. The piece that is cut off is the inside backer for when you bolt it together.

Installed a handful
My BHM has an Airmar b260 the blue fairing block is huge (2ft long)
Location for the install is key.
Then you have to figure the dead rise angle, mine was 5 degrees.
Mounted it in a tilted fence band saw for the cut. The piece that is cut off is the inside backer for when you bolt it together.

A critical piece to consider. Good post, Ron. While the saw is set up, cut a second block of wood or plastic as a back up. Sometimes the cut off of the blue block gets dinged up, or won't fit in the bilge between stringers. I have also seen the inside backer cut too thin. In that case, just add a block to the backer. May have to countersink to reach the transducer for securing. Use the cutoff as template BEFORE installing. (Had to do this fix for a friend who had already installed with 5200, so I was drilling blind from the inside...)

Sandman,

Don't let this scare you, if you are handy it really isn't a big deal.

I installed a similar ducer as Ronnies, just a bit shorter maybe a 15" B744.

I used epoxied plywood as a backer, my location was a zero deadrise spot on a stiffner rake.

Is is important to dryfit this together and actually put everything in the hole including the paddle wheel if you have a speed transducer too. Short story......I have everything ready to go and fit it, then found out shortly after that my speed attachment wouldn't bottom out and seal for the backer block was too thick. So picture wet 5200 on everything snaking cable thru nuts and everything to take this apart to install a thinner block. Yeah it was a bit messy to say the least and just a few cuss words......

As for ducers with the speed paddle wheel I wouldn't bother spending the extra money for this thru the water data. You really don't use it and is just approximate anyway.. Just another thing to maybe go wrong in the bilge.

Some good points by Beamie
Dry fit as many time as necessary before installing with either 4200 or 5200. That stuff can make a mess.
Be sure to remove all bottom paint, sand, wash with acetone areas to be sealed, inside & out.
Should you be removing an old thru hull & need to drill bigger hole (think mine was 2inch) hot glue a scrap piece of wood inside to have a pilot hole for correct bigger hole saw size. Hot glued wood will pop off easy enough later.

I knew there would be stories....

Beamie: I can imagine...wet 5200 sticking to everything...sticky rags galore I bet! You probably still have that $hit on your hands

Ronnie... that is the beast. When I saw that I said..."certainly not a "plug and play" job, eh?" I knew there had to be some install stories behind installing these.

I have to dig the old one out first and make a larger hole I am sure but I don't have all the details just yet.

I took a pic of what I have installed now. I like the current location. It is in frond of the engine and awkward to work around in the bilge but from a external hydrodynamic standpoint it is in a low disturbance location along the keel.

I may need several transducers installed (regular sonar + side scan) and I think the side scan needs 2.

Geez Sandman,

Oh boy,like you started off saying, more involved.........

That looks like an awlful place to be right on that stiffner strake. above or below it would have been better but that depends on inside accessibility. I would say that was a mistake and they made it work or it had to go there to get at it inside. Dealing with a fairing block in that same area would not be easy. May have to just plug that one up permanent and relocate new.

Which way is that one shooting now? Is it verticle on the inside or is it one of those self leveling internal jobs?

Yes need one either side of keel for structure scan. You probably don't have a keel like a downeast boat though do you.

Was on a buds boat for just a short time and he showed me his side scan. He still finds the fish on the regular unit many times but this is real nice for the structure when it comes to bottom fishing rocks and recs. A bit pricy but very cool if you have the budget and room. He just had the scan unit part for everything else on the multifunction he already had seperate units.

Fwiw I just put a 28khz furuno black rubber block transducer for now its just sitting in the bilge shooting thru. Also A 200kHz rubber transducer on the same unit, shooting thru. The 200 i mixed 5 min epoxy and just stuck it down. The 28 is just floating around untill i figure out prime location, but where it is now is pretty great. The pic is great. I plan on making a box/ well this winter it can sit in with saltwater.
My point is shoot thru might be another option to consider
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If you have the space you can install a tilted element airmar.
No need for fairing at all, they sit flush and tilt the element instead of the ducer body. GEE what a concept.....

I have 20 DR, and it works great on my furuno.
There is a 1KW tilted. I didn't need that depth so I got
a 600W.

Is the hull cored? That will make a big difference.

Yeah...the hull is cored and the current transducer sits along the CenterLine in a flat-ish spot inside. I don't know if it is cored along the keel . I have drilled thru sections of the transom and sides to install thru hull fittings and have that section.
I have plenty of room on both sides of the engine and in front of it as well.

I worry about the shoot thru. The acoustic signal will have to pass through several layers of material of different densities...both ways.

Yeah...the hull is cored and the current transducer sits along the CenterLine in a flat-ish spot inside. I don't know if it is cored along the keel . I have drilled thru sections of the transom and sides to install thru hull fittings and have that section.
I have plenty of room on both sides of the engine and in front of it as well.

I worry about the shoot thru. The acoustic signal will have to pass through several layers of material of different densities...both ways.

1) if the hull is cored a shoot-through installation won't work well.
2) When you install the transducer you have to remove some of the coring around the hole so that you can fill it with epoxy to prevent water intrusion. A wet cored hull is not something you want to deal with. Remove at least 1 inch of coring all around the hole and pack it with epoxy and cabosil mixture before you install the transducer.