Depth sounder

I am looking to install a depth finder in my 1983 36 Albin Trawler. the dead rise is about 27-28 degrees... what type of sounders are most folks using . I want an in hull transducer that I will be installing my self. I had bought a faria sounder with an in hull transducer but the max dead rise is 22 and I could not get it level ... Thanks in advance for some suggestions on depth sounder for my boat .. or what I could have done to make the faria sounder transducer work.
Kevin G
New Bern NC

I have one of the adjustable shoot through the hull airmar for my Raymarine e7 display.

It may have been limited to 22 degrees, but where I mounted it, it was close enough.

For a standard 50/200 ducer, between beam angle and how they register depth....usually within 10 degrees or so of vertical is accurate enough for everyone except bottom surveys.

Often keeping them far enough away from the keel to avoid problems with a keel is an overlooked issue.

And don't worry about putting it in the engine room.

If in doubt, you can always just use clay or any other temporary sealant to see how it is working, move if bad, make it permanent when sure OK.

The original Ray Jeff depth sounder in my Marine Trader was mounted in a wooden fairing block. Wood blocks are infinitely adjustable to any dead rise. So too are the new fangled plastic blocks. Don't be afraid to break out the planer.

I like the idea of temporarily mounting the transducer inside the hull to test out various locations. I had one temporarily mounted in a sail boat for 5 years.

"This is only temporary, unless it works".

Kevin, Scott has some good advice. If you're in 400' of water, the error could be noticible but in 30', it will be negligible. Make sure you're not shooting thru a cored hull or it won't work, and over about 5/8" of solid glass will be detrimental also. On my previous 44MT, I had two transducers (in-hull) mounted in my engine room and they were very accurate. Make sure they're not just behind any thru-hull also. Ben

I have an Airmar P79 through the hull transducer connected to a Garmin system. I was able to mount mine on an almost horizontal surface so the adjustment feature wasn't really necessary in my case.


I calibrated it using a boat pole in shallow water. That's where it matters to me.

I don't understand why anyone would mess with the fairing blocks when you can just buy a through hull transducer with the offset angle built into the through hull fitting. The transducers come in several different offset angles and the housing sits as close to the hull as any standard through hull fitting. Am I missing something?

Not quite sure why the average boat owner doesn't buy shoot thru the hull ducers and avoid the issue of another thru hull.

Not because I think you will ever sink from one....but just all the other associated stuff.

I have a broadband sounder and use it to find fish and water temperature as well as the bottom. I have serious doubts that a shoot through the hull transducer is as capable in that capacity. When I installed a low power LED depth only unit as a "sleep on" alarm I didn't have those concerns, just whether it was getting too deep or too shallow.

Are you sure that your deadrise is 28 degrees? That would put your hull into a deep vee range. My 41' President deadrise in the front of the engines is about 15 degrees. Most semi displacement trawlers do not approach the high 20s in deadrise. Why don't you measure it again and see if it is really that high. The reason you can't find a transducer in that range is because not many boats have that high a deadrise. I took a digital angle gauge (mine is made by Wixey) and measured the deadrise where I wanted to install the transducer. You can lay a board across your stringers and zero the gauge. Then place the gauge where you want to put the transducer and read the angle. It is very easy to do and much cheaper that buying the wrong transducer.

That 22 deg TD will read fine in <60ft or more.
Im amazed that a 30+ YO trawler doesnt already have at least one TD already in place. My boat had FIVE! NONE were longer connected to anything!
The problem with shoot-through-the-hull transducers is the transducer wont work if the hull is cored or air gaps in the lamination. You need to be sure. One way to check is to put the transducer in a plastic bag of water, lay that facing down in the bilge, and check to see if it reads ok. If not, move it to several locations in the bilge until you find a good spot. If still no good, you may have to go with the traditional through-hull with a fairing block or angled TD.

I have installed shoot through the hulls in cored vessels.

The Airmar site shows you how they reccomend.

True a shoot through won't provide water temp but a sensor can be mounted elsewhere or not a big deal for many.

The new shoot through have nice liquid retainer rings where they can be set on any temporary seal such as modeling clay or butyl tape and a dash of water. Pop in the ducer and check. If not a good spot, pull up and move...really nice.

Unless looking for ultra high performance, and I am not familiar with CHIRP tech, most shoot through will give adequate performance for all but perfectionists.

I have the Airmar P79, but angle is very low on my boat. It works well, have hooked it up to a new garmin MFD recently as well. I did have to replenish the fluid recently.

If your cruising waters are shallow it may not make much difference how you install it. Where I cruise the water depth can vary from hundreds of feet to thousands as I cross the mouth of a bay in transit. I am annoyed by having my MFD alarms constantly telling me it can't find the bottom, or (if it can't find the bottom) making anything it can detect from a thermocline on into the bottom.

If you already have a hole in your hull and fairing blocks, I see no point in going to a shoot through the hull solution. Which was my original point...

I already had a hole in mine, I just drove a plug into it and used the plug to keep my hole saw centered for the new (larger) hole for the broadband sensor.

I just installed an Airmar P79 in hull transducer for our new Simrad GO9. I have to say I'm very impressed with its performance as installed iaw the instructions. Airmar have just released a new range of in hulls including chirp models.

Our hull is only 12 degrees where the transducer is measured with an app on the iPhone. I don't know that you'll find one to compensate for 27-28 degrees but you could built your own wet box in the hull out of pvc pipe.

Kevmar, when I was trying different locations to mount in my thin, single skin hull, I just placed the transducer in a plastic ziplock of water. There were pretty much no air bubbles to destroy the signal. Then test different spots. It was not a sophisticated unit I was using, but it seemed to work fine.

My transducer sticks out from the hull. Presumably because it is steel.