How to remove airmar thru-hull housing for depth sensor

All,
Looking for your advise. I have old airmar thru-hull depth sensor which is a retractable tube inserted into 2inch plastic housing in the boat hull. I need to remove it to replace it with at 2 inch fish finder. How do I go about removing the plastic thru-hull housing ?

Thanks,
Roman

What are the diameters of the shafts of the old and new though hull fittings (what size hole do you have? What size do you need?)?

Ted

I had to change my Airmar transducer once because the temperature started showing nice, warm 34 degrees C. here in Sweden on a cold November day. It only got worse...and internet research said change it.

So, I had it changed when the boat was out of the water for the winter. BUT, I noticed in my box of bits & bobs and yet-to-be identified stuff that came with the boat, an AirMar "blanking plug" that is intended to screw on in place of the transducer. So, if your fish finder is Air Mar...and sort of "plug & play" and if you're thinking of trying to make this change while the boat is in the water, it might be nice to have this plug handy, if you find that you have one on board. See photo below.


Apologies, if this response turns out to be totally irrelevant!!

Romanp said:

All,
Looking for your advise. I have old airmar thru-hull depth sensor which is a retractable tube inserted into 2inch plastic housing in the boat hull. I need to remove it to replace it with at 2 inch fish finder. How do I go about removing the plastic thru-hull housing ?

Thanks,
Roman

Click to expand...

I am not sure what exactly you are asking. If you just want to pull the thru hull out of the assembly and put a new one in, then there is usually a screw on ring on the top that you unscrew in order to pull the insert transducer out.

If you are changing the entire assembly and need to get it all out of the hull in order to put a completely new transducer in then it depends on how it is installed. Chances are that the transducer is installed with 5200 which is very tough to get out. I would probably use a multi tool and just cut the old transducer out. I did one on my boat last winter and the multi tool allowed me to cut one side off flush with the hull and then pop the other side out. I was just getting fir of the transducer so I glassed the opening closed.

I note, now, that the OP said "housing". So, kindly disregard my prior response, RomanP!

It would really be helpful to know the model. Otherwise, we're all just guessing. There are usually labels on both ends if the cable and also a way to look in the MFD to see the transducer it is set to talk to.


If wildly guessing, what you are describing seems to be an arrangement similar to an airmar B744V. If so, this doc should explain how to remove the insert, itself, or the insert and valve together. If you need to remove the transducer body, that is done from the outside.

http://www.airmar.com/uploads/InstallGuide/17-438-01.pdf

O C Diver said:

What are the diameters of the shafts of the old and new though hull fittings (what size hole do you have? What size do you need?)?

Ted

Click to expand...

The point I was trying to make was that if you required a larger hole through the hull, there is a technique to bore the larger hole without removing the existing transducer sleeve.

Ted

Comodave said:

Chances are that the transducer is installed with 5200 which is very tough to get out. I would probably use a multi tool and just cut the old transducer out. I did one on my boat last winter and the multi tool allowed me to cut one side off flush with the hull and then pop the other side out.

Click to expand...

Same issue. Installed with 5200. Same solution. Cut it out with multitool.
If you're in the water yard can do a short haul where they leave you in the slings for an hour. If you need more time they will put you on blocks but rate goes up significantly.

I was on the hard so took the time to redo the fiberglass around the old transducer opening.

I have this type of the setup, It comes with a 2inch housing then then insertable transducer https://rm.factoryoutletstore.com/d...er.html?category_id=20261&catalogitemid=16209

What I've purchased is P319 2inch transducer but unfortunately I can't insert it into the existing housing as the transducer itself is 2inch wide

https://rm.factoryoutletstore.com/d...er.html?category_id=20261&catalogitemid=16209

Now now I need to figure out how to remove the old housing which is glued with 5200. I hear people use multitool. Do you mean Oscillating Tool ? have one but I'm not sure how would I approach cutting it out. Let say I cut off the head of the transducer which is at the exterior of the boat, now I have a shaft with the threads and 5200 glued to the hull, how to get that out ?

I was hoping that airmar engineers would have installed notches inside of the tube so I could use thruhull puller to unscrew it out of the boat, but I don't think their engineering thought goes that far. And if you are in the business of making tranducers why wouldn't you design ONE size housing and all other transducers could be just inserted into it ?

SoWhat said:

Same issue. Installed with 5200. Same solution. Cut it out with multitool.
If you're in the water yard can do a short haul where they leave you in the slings for an hour. If you need more time they will put you on blocks but rate goes up significantly.

I was on the hard so took the time to redo the fiberglass around the old transducer opening.

Click to expand...

My boat is on the blocks so I have access to the bottom of it.
I'm not sure I understand, if I cut out the head of the sensor from the bottom, I still have the shaft of the tube inside of the hull, how do I get that thing out ?

I was thinking to use a monkey wrensh, grag the tube inside of the boat and start turning it counterclockwise and see if 5200 will give way and I can unscrew the whole assembley out of the boat ? I was actually thinking about removing the inner transducer and use resiprocal saw to cut along the length of the housing in several places and then try to remove the separate pieces with a chisel

I've seen fiberglass delaminate before 5200 would give way.

Would you consider leaving the old one in place/abandoned and the new one epoxied inside the bilge? Or just install it in a different spot. 5200 is a blessing and a curse. I believe the other poster is saying he cut out the fiberglass around the transducer and then repaired the huge hole left behind. Please correct me if I misunderstood SoWhat.

Swfla said:

Would you consider leaving the old one in place/abandoned and the new one epoxied inside the bilge? Or just install it in a different spot. 5200 is a blessing and a curse. I believe the other poster is saying he cut out the fiberglass around the transducer and then repaired the huge hole left behind. Please correct me if I misunderstood SoWhat.

Click to expand...

I cut the old one out with a mutlitool.
I then used coarse grit on DOA sander inside and out to smooth surfaces and remove 5200.
Then a dremel to smooth out edges of hole.
Reglassed to build up thickness and to ensure core was sealed.
Sanded, recut hole, and reinstalled with 4200.
Holes were similar in size.

No problem leaving old one in and cutting new hole. Just make sure edges are sealed with epoxy to protect core and laminations.

I would not epoxy in-hull for a fishfinder. Fine if you just want depth but shooting through fiberglass will lose some resolution.

There is a technique where you double stack hole saws on a single mandrel. The smaller hole saw acts as a guide in the existing housing hole. The larger hole saw cuts the desired hole. In this situation, you're basically boring out the plastic housing to reuse the hole. Obviously there will be some cleanup of the remaining 5200 in, and on both top and bottom surfaces of the hole. Likely a drum sander on a drill would clean out the hole.

I don't see you removing the plastic housing in one piece, if bedded with 5200.

Ted

The other technique to refill with a hole saw is to insert a wood plug in the existing hole. That let's you use the normal hile saw with a pilot drill/hole in the plug
.

O C Diver said:

There is a technique where you double stack hole saws on a single mandrel. The smaller hole saw acts as a guide in the existing housing hole. The larger hole saw cuts the desired hole. In this situation, you're basically boring out the plastic housing to reuse the hole. Obviously there will be some cleanup of the remaining 5200 in, and on both top and bottom surfaces of the hole. Likely a drum sander on a drill would clean out the hole.

I don't see you removing the plastic housing in one piece, if bedded with 5200.

Ted

Click to expand...

[emoji106][emoji106]

It ain't gonna be easy no matter how you attempt to remove the old one. Just think twice to avoid getting in over your head. Leaving the old one intact, abandoned and cutting a new hole is simple, straightforward and unlikely to create any new issues. If you decide to try and remove the old one be prepared to have the boatyard fiberglass dept to step in just in case. I truly wish you luck whatever you decide to do.

SoWhat said:

I cut the old one out with a mutlitool.
I then used coarse grit on DOA sander inside and out to smooth surfaces and remove 5200.
Then a dremel to smooth out edges of hole.
Reglassed to build up thickness and to ensure core was sealed.
Sanded, recut hole, and reinstalled with 4200.
Holes were similar in size.

No problem leaving old one in and cutting new hole. Just make sure edges are sealed with epoxy to protect core and laminations.

I would not epoxy in-hull for a fishfinder. Fine if you just want depth but shooting through fiberglass will lose some resolution.

Click to expand...

OP said it was a depth finder not a fish finder.

I really don't believe this is so hard or time consuming as to be worth making another hole in the boat. Cut it in a small few places longitudally with a hacksaw or multitool, take it out in pieces, clean it up, and reuse. It is just time and effort, not brain surgery.

Swfla said:

OP said it was a depth finder not a fish finder.

Click to expand...

No, OP wants to install a fishfinder. He is removing a depth transducer.
"I need to remove it to replace it with at 2 inch fish finder."

SoWhat said:

No, OP wants to install a fishfinder. He is removing a depth transducer.
"I need to remove it to replace it with at 2 inch fish finder."

Click to expand...

You're right. Removing depth finder and replacing it with fish finder. Only reason this even mattered to me was that's it's not uncommon to mount transducers for fish finders on multi-million dollar custom sport fishers to keep the bottom as smooth as possible. It has to do with top speeds and no turbulence to spook sport fish when trolling surface baits. These guys are finicky and superstitious. No bananas allowed on the boat. LOL. Any kind of air across the face can give erratic readings. A common issue for smaller boats with a transom mount transducer that is mounted in a spot that sees air from strakes in the hull or some other turbulence. Another concern for mounting in the bilge is if the hull has air spaces in it. Of course a properly laid up hull has no air bubbles.

However you decide to attack this, it's all fixable in the end.

It isn’t that hard. Take a multi tool and cut off flush to the hull which ever side is easier to access. Particularly if the housing is plastic, it will cut very easily. Then cut off the other side. Now you just need to clean out the hole or do like Ted suggested and use 2 hole saws, 1 inside the other and cut the new hole to the proper size. If the holes are too close in size that you can’t get the smaller hole saw inside the larger one, get a dremel tool and carefully grind away the old fitting in the hole and slowly enlarge the hole to the size you need. Probably an hours worth of work if you have good access to the fitting. I have done this with bronze transducers and a plastic one will be easier by far.

It's really not necessary to cut the flange off the bottom and the nut off the top before hole sawing the core out. The hole saw will cut right through the plastic. What remains of the plastic can be removed with a sharp chisel flat against the hull.

Ted

gkesden said:

I really don't believe this is so hard or time consuming as to be worth making another hole in the boat. Cut it in a small few places longitudally with a hacksaw or multitool, take it out in pieces, clean it up, and reuse. It is just time and effort, not brain surgery.

Click to expand...

That works too. Some heat with a heat gun might loosen it up depending on the sealer that was used. Just do it, you'll get it out one way or another.

A two inch hole saw will probably follow the old hole through the adhesive and plastic without straying if you want to go that route. The new transponder will work even if the hole is a little oversize.

SoWhat said:

No, OP wants to install a fishfinder. He is removing a depth transducer.
"I need to remove it to replace it with at 2 inch fish finder."

Click to expand...

Semantics. They are one-and-the-same thing. They both hydroacoustic transducers. They both show bottom. One may provide additional information based on software for interpretation of the return target strength. One transducer may be dual beam, multibeam, newer technology, etc. But they both use hydroacoustics technology.

I had to remove an old housing from the hull. Luckily, I was able to put a pipe wrench on it and unscrewed it from the outside. Other alternative is to use a hack saw blade and make veritcal cuts. Then you can chip it out with a big screwdriver and hammer. Next time, all you need is silicon to seal any drops of water that may seep in. There is no structural integrity to worry about. The new unit will fit very snug. Dry fit and then use lots of silicon to seal.

I would just drill a pilot hole through the center of the transducer, then with a with a hole saw slightly undersized redrill, then using a dremel sanding drum grind the remains of the old unit out and replace it. I have removed many through hulls this way, it's very clean. If the new transducer is larger than the existing one, it's even easier to just center drill the transducer and then use a new hole saw of the appropriate size to make a new hole.

Hi RomanP, I hope it's easier than anyone anticipated. Please let us know how the project went. We can all learn from you.

AKDoug said:

I would just drill a pilot hole through the center of the transducer, then with a with a hole saw slightly undersized redrill, then using a dremel sanding drum grind the remains of the old unit out and replace it. I have removed many through hulls this way, it's very clean. If the new transducer is larger than the existing one, it's even easier to just center drill the transducer and then use a new hole saw of the appropriate size to make a new hole.

Click to expand...

He said the transducer removes from the shell that is in the hull. He wants to remove the shell if I understand him correctly. That should be simple as he said it is a plastic shell.