GPS/Sonar - Transducer Mounting

I

imspacemancraig

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Joined
May 24, 2009
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31301
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543
Hey all,

I have a '86 32 Mariner. I want to replace the depth finder and put in a GPS/Sonar. I have the unit picked out, but began to think about where to put the transducer. The one for the depth finder right now looks to be as old as the boat and is mounted mid-ship through the hull in the bilge area below the floor in front of the fridge/sink. From what I have read, generally the preference is to have the transducer closer to the rear of the boat. So, I am not sure if I should move it further back or reuse the same spot?

Any suggestions or comments would be helpful. Hard to say, but not even sure if it is still in the water when on plane, but seems to work ok (well at least until this past summer when it started to turn off/on on its own without a rhyme or reason).

Craig
 
My depth transducer is mounted just forward of the starboard engine's cooling water intake scoop. This is just about dead center front-to-rear.

The general wisdom is that you want the transducer in "clean" water. Anything on the hull, such as strakes, thru-hull scoops, and underwater running gear is going to form turbulence that you don't want near the transducer, which usually means the further aft you go, the more likely you are to encounter these appendages.

So it if seems to be working OK now, I would leave it there - especially if that means patching an old hole and drilling a new one...
 
Hmmm, I didn't notice where the cooling water intake is, but yes, seems like the transducer is about the middle of the boat from bow to stern. Makes sense on the turbulence and I am guessing if it worked in the past, that it is still in the water while on plane (hard to look over the edge moving lol).

The patching and drilling a new hole is a concern, but thinking I would just leave the old one in place if I located the new one somewhere else. I have some trepidation over drilling a new hole, although I think I may have to bore the old hole to make it a bit larger for the new transducer to fit through.

Speaking of which, after drilling the hole, should the exposed sides of the hole in the hull be sealed before putting the transducer in and then seal that? Or does just sealing the transducer in well do the trick?

Also, does anyone know the dead rise of the hull on the '86 32 Mariner? Need to buy the right transducer so it mounts level from what I can tell.
 
Just punch out the old and use that hole, that is what I did. Mine is forward of the starboard engine, inboard and a little forward of the raw water intake. It works great in that location. My engines are midship. I only go 13 -14 kts so maybe I don't make enough turbulence to matter.

Good luck
Niles
 
With any underwater hole, especially if the hull has coring (balsa or foam), it should be sealed, otherwise you could have severe damage to the hull. What I like to do is to seal the hole edges with a good epoxy such as West System, then when cured, use your favorite sealant (101, 4200, etc) and seal the transducer.

There are two objectives here (1) sealing the edges of the fiberglass/coring so you do not get any water damage, and (2) sealing the transducer so you have no leaks around it.

Even if the hull has no coring, I still like to seal the edges as a best-practice.

Depending on the transducer you use, some of them have an articulated mount, so when you twist it, the angle changes.

Others have a faring that is maybe 12" long (or longer), and its made of a plastic material, and you have to put it on your table saw or band saw and cut the right angle in it.

And some just mount flush so they are not pointed directly down.

The transducer I have is an Airmar P-79, which is OEM for several of the popular sonar systems. It is an in-hull transducer rather than a thru-hull, and you don't have to drill a hole.

You simply glue the transducer ring to the inside of the hull bottom, then fill it with pink antifreeze, and place the transducer in the top. The pink antifreeze couples the transducer to the hull. And this transducer is one of the articulated mount types so you can line it up so that it shoots straight down regardless of your deadrise.

However, it will not work with a cored hull, only a solid fiberglass one. A cored hull attenuates the signal too much.
 
quote:
Originally posted by nwaring

Just punch out the old and use that hole, that is what I did. Mine is forward of the starboard engine, inboard and a little forward of the raw water intake. It works great in that location. My engines are midship. I only go 13 -14 kts so maybe I don't make enough turbulence to matter.

Good luck
Niles

Click to expand...


+1 I didn't do that, made a new hole for the new transducer and just left the old on in place. Later had to go back and take it out and glass over the hole because of a leak.

Also, if thew model number ends in 7 your boat has a solid hull below the water line. No coring to worry about.

Bob
 
Thanks for the help...

awboater - That is what I was thinking too, rather it all be sealed and not worry about it! The GPS/Sondar I am getting is the Garmin 421s. I want to use the through hull as it gives speed, depth, and temp readings. More about the toys. :) I will need to look at the transducer that I was planning on and see how it is made to fit. I was looking at the bronze through hull from Garmin (model: 010-10193-01).

rnbenton/nwaring - pretty much what I was thinking as well, use the same hole.

I will have to go back to my manual, can't remember off the top of my head if my boat model ended in a 7 or not...
 
I have an '86 32' Mariner too. It is the 3297 and all fiberglass hull, but you still should seal the edges to prevent water from getting into the laminate. I want to say the deadrise is 7 degrees but don't quote me on that-and deadrise is measured at the stern. Where you want to mount the transducer is 5-7 ft ahead of the stern and the deadrise is much greater therey. I believe you just by a planing block and cut/shape it to fit your hull instead of matching a transducer to fit the hull deadrise-although if the sell transducer with varying degrees of pitch, that could save a lot of time and labor.
 
I like the new transducers with built in element tilt. I just purchased a Airmar B-60 that will flush mount in the hole left by my old transducer. (Airmar makes transducers for a range of hull angles. In the one I purchased there are three angles) That way I do not have to fool with fairings or any thing like that. The transducer on my straight drive engine boat is located just forward of the engines.

G

I have somewhere (maybe on the Airmar site) that shows about 1/3 back from the bow to be the preferred location for a foat with straight drives.

G
 
Yep, looks like I have the 3297 as well. Planning on sealing inside before adding the transducer.

gcolton - the Airmar site is a bit behind in the world of website... any clue if the one you have works with a Garmin? The Garmin I plan on getting is the 421s. It is NMEA 2000 so I assume it is.

As for the dead rise... guess I need to make a trip up to the boat this weekend and take a look underneath. Anyone know where I can find a digital level to figure out the dead rise? According to the Airmar site, if less than 10 degrees, may not need to worry about it... not sure if that is correct or not.
 
The Garmin 421 uses garmin # 010-10182-00 or 010-10182-01 for the transducer. That cross refs to the airmar B117. That one doesn't have the adjustable angle but I think the B60 would work also, call Airmar.

Good luck
Niles
 
Niles - I was actually thinking about transducer model number 010-10193-01. Aside from the looks of it, what is different about these two types of transducers? This one is sort of what looks like what I currently have and I would need to bore a much larger hole to fit either of the two you mentioned.
 
quote:
Originally posted by imspacemancraig

Yep, looks like I have the 3297 as well. Planning on sealing inside before adding the transducer.

gcolton - the Airmar site is a bit behind in the world of website... any clue if the one you have works with a Garmin? The Garmin I plan on getting is the 421s. It is NMEA 2000 so I assume it is.

As for the dead rise... guess I need to make a trip up to the boat this weekend and take a look underneath. Anyone know where I can find a digital level to figure out the dead rise? According to the Airmar site, if less than 10 degrees, may not need to worry about it... not sure if that is correct or not.

Click to expand...


The B-60 that I am on the way to the boat to install, has a Gramin plug. You order it to fit whatever manufacturer unit you will be using it with. In fact it even has a Garmin part number and Elaine at Boatfix says that Garmin is the point for warranty work.

To determine the correct deadrise just call the manufacturer of the boat. I called Pursuit and they gave me the data I needed. I told them exactly where the transducer was to be mounted.

The B-60 takes a 2 3/8 inch hole.

George
 
The 010-10193-01 is a triducer. It adds a little wheel for speed. That would be airmar # B744V or B45. It does look like a smaller hole. If you go with that one make sure you don't mount it where the slings pick up your boat.

Good luck
Niles
 
The mount point would be in the center of the boat, so should be OK, but I see what you mean.

Aside from the material, what's the difference between the brass transducers and the plastic ones? Are they any better? Price seems to be a difference too...

George - please post some pictures or at least how things went. Are you swapping it out for an existing one or starting new?
 
quote:
Originally posted by imspacemancraig

The mount point would be in the center of the boat, so should be OK, but I see what you mean.

Aside from the material, what's the difference between the brass transducers and the plastic ones? Are they any better? Price seems to be a difference too...

George - please post some pictures or at least how things went. Are you swapping it out for an existing one or starting new?

Click to expand...


There is really nothing to take a picture of.

We swapped out yesterday. The old transducer was in a 2" diameter hole and the new B-60 needed a 2 3/8" hole. Using a template (real simple template, just a piece of ply wood with a 2 3/8" hole) we drilled out the hole to the new size. You need the template because there is nothing for the centering bit to bite into.

The biggest problem was getting the nut started off on the old unit. Would up having to go home and get a cold chisel and 3# hand sledge. Once you can get the nut moved it can be turned off with a pipe wrench or large slip joint pliers.

There is nothing to take a picture of because nothing really sticks below the hull. I coated the area (including transducer lens) with water based hull paint. If I took a picture you would just see a black hull.

No problem running the wiring (at least in my boat. Plugged it in and all doing good.

It is a two man job because you have to pass up the wire and insert the transducer from the bottom.

I do not have the boat back in the water yet. Forty Four degrees out there now and light mist. Wanted bottom paint to dry over night so did not put the boat back in yesterday.

I do not know that there is any performance difference between plastic and brass transducers. I believe the biggest advantage is lifetime.
 
OK, after some research, looks like the B-60 is the way to go. Only question I have is, how long is the cable that comes with it? I can't seem to find that out anywhere... I need enough to get from the hull to up top by the captain's wheel and from the looks of it, it winds it way up through to the v-berth before going up top... Haven't quite figured out where it goes... but guessing I need some length to make it work.

Also, to mount the GPS up top, I am thinking I need to detach the steering console and lift it up. Any tricks to this? Looks like I may have to remove the screws that attach around the wheel as well as the screws around the entire console. Any ideas or words of wisdom?
 
I have an extra B60 with the Lowrance/Simrad cable. I purchased the 12 and 20 degree versions for my boat because of a special deal I got on them. I'll figure which one I'm not using and let you know. I would be looking for $175 and I'll pay shipping. The B60 comes with a cable that ends with a 5Pin and you can purchase the extension cable from the 5 pin to whatever you need. I'll be installing mine maybe next week if the snow melts. I also will be goign from a 2" to 2-3/8".

MJK
 
Thanks, but I need one that will work with a Garmin 421s. I will be headed up to check and see what my deadrise is, but right now thinking I need the 12 degree (but not positive).
 
I don't know the length of the cable but I know I had plenty. On mine it was a straight shot from the hull up the starboard side wire raceway to the bridge and over to helm which is centered.

Good luck
Niles
 
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