Through Hull Transducer Install...

[Keitha]

I just installed a new Airmar B175HW through hull transducer in my 232 Gulfstream. When I bought the boat, it had an abandoned through hull installed. This new B175HW is much larger - 3 3/4" diameter. The good news is that the hole saw fit over the old transducer, so I did not have to wrestle with trying to uninstall it. I just cut it out as you can see in the pictures:
Once I got the hole cut, I sanded the bottom paint from the mating surface of the hull, taped over the transducer, cut the tape to leave a clean barrier, and cleaned it with Xylene. I also cleaned the inside of the hull where the rubber gasket will seal. Taking the time to tape well really makes clean-up a breeze.
I test fit the transducer a few times to ensure it is seating properly. I then fed the wire through the hole and applied a thick bead of West Marine 8200 sealant around the flange of the transducer. I inserted the transducer into the hole and taped it in place from the outside. Ensure that you see plenty of sealant squeeze out from all around the transducer flange.
Make sure that the arrow on the transducer is pointing directly to the keel (center line of boat). This one is a 20* tilted element that need to be facing the right way so it fires straight down.
I was then able to add more sealant around the transducer on the inside prior to installing the rubber gasket, the plastic spacer, and the large nut.
I used a couple pair of large channel lock pliers to hold the transducer from spinning while I securely tightened the large nut. I snugged it down as much as I could, then tightened the two locking screws on the nut.
Then clean up: This is where time spent taping good pays off. I just pealed the tape on the bottom and all the dripping sealant came off with it. A quick smoothing of a bead of sealant around the flange and it is done.
Lastly, I fed the cable through the hull conduit and up behind the instrument panel.
I need to give the adhesive sealant a few days to fully cure before I try it out. I hope to put it in the water this weekend.

 

[seasick]

I hope you never need to remove that thing

 

[DennisG01]

Good thinking (and bit of luck with the sizing!) on just using the hole saw right over it.

Along the lines of what Seasick said... I don't know anything about WM8200... but if it's like 3M5200 (check the psi strength), yeah, that is totally the wrong stuff for this application. 3M5200 is basically super glue - regardless of what it says on it's label/applications, there's really very few uses for it on a boat. All that's needed here is a sealant, not an adhesive. Anyone that does lot's of work on boats (as opposed to internet "experts") will cringe if they hear that someone used 3M5200.

 

[Keitha]

WM 8200 is an equivalent to 3m 4200 - I've used it more than once and it is good stuff and not impossible to remove.
It is private label of Starbrite 8200
I think West Marine does themselves an disservice on how they brand it 8200. People see 8200 and correlate it with 4200 and 5200 (number is higher, it must be stronger...). That is just not the case - I've used all three products.

From West Marine:
Our Quick Cure Polyurethane caulk is ideal for installing hardware and thru-hulls that require a solid, but flexible seal. When cured, this polyurethane caulk forms a strong, flexible bond to fiberglass, wood, painted surfaces, metals and plastics. This flexible quality maintains a seal when hardware is loaded; as is often the case with cleats being loaded by docklines. Thru-hulls benefit from the same flexible seal as bronze, stainless steel, and plastic expand at different rates than fiberglass and wooden hulls. We recommend masking hardware edges and surrounding areas to prevent contamination and reduce clean up times. For a bond and seal you can count on below or above the waterline, grab a tube of West Marine Polyurethane Adhesive Sealant.

 

[DennisG01]

OK, that's good, then. 4200 is fine. Truthfully, I don't buy anything from WM because it's usually just re-branded stuff (not always, but often at a premium price) and I don't feel like taking the time to research it! Thanks for responding back on that.

 

[seasick]

I don't know if WM 8200 is rebranded Starbrite 8200 but Starbrite 8200 is intended for permanent applications just like 3M5200

 

[Holokai]

WM 8200 is an equivalent to 3m 4200 - I've used it more than once and it is good stuff and not impossible to remove.
It is private label of Starbrite 8200
I think West Marine does themselves an disservice on how they brand it 8200. People see 8200 and correlate it with 4200 and 5200 (number is higher, it must be stronger...). That is just not the case - I've used all three products.

From West Marine:
Our Quick Cure Polyurethane caulk is ideal for installing hardware and thru-hulls that require a solid, but flexible seal. When cured, this polyurethane caulk forms a strong, flexible bond to fiberglass, wood, painted surfaces, metals and plastics. This flexible quality maintains a seal when hardware is loaded; as is often the case with cleats being loaded by docklines. Thru-hulls benefit from the same flexible seal as bronze, stainless steel, and plastic expand at different rates than fiberglass and wooden hulls. We recommend masking hardware edges and surrounding areas to prevent contamination and reduce clean up times. For a bond and seal you can count on below or above the waterline, grab a tube of West Marine Polyurethane Adhesive Sealant.

I’m looking at installing a b175m soon and looked up 8200 on the West Marine site. For some reason it’s all on clearance and a few of the reviews mention some of the cartridges being old and half-cured. Dang, just when I thought I’d found a reasonably priced alternative to 4200...

Also, google found this article. A little dated but still a useful read:

The Great Stickup: Practical Sailor Tests Marine Adhesives, Caulks, and Sealants - Practical Sailor

Since 1974, Practical Sailor’s independent testing has taken the guesswork out of boat and gear buying.

www.practical-sailor.com

 

[DennisG01]

I’m looking at installing a b175m soon and looked up 8200 on the West Marine site. For some reason it’s all on clearance and a few of the reviews mention some of the cartridges being old and half-cured.

The same thing happens with 5200 - you'll find it on sale because it goes bad quickly. I get them shipped to the marina for sale and even then, some of them are already bad.

 

[Keitha]

OK, Now that we got Caulk Talk out of the way...

I am looking forward to splashing the boat - hopefully this weekend to try out the B175HW. I will try to remember to get some screen shots.

 

[seasick]

The same thing happens with 5200 - you'll find it on sale because it goes bad quickly. I get them shipped to the marina for sale and even then, some of them are already bad.

I try to test all sealant and adhesive cartridges or tubes (including silicon) by squeezing near both ends and the middle. If the middle is soft but the nozzle end is very firm, the goo has probably started to cure.
One trick for longer life that I can attest works is to put an opened tube of 5200 in a freezer. I have had previously opened tubes last 2 years!

 

[DennisG01]

One trick for longer life that I can attest works is to put an opened tube of 5200 in a freezer. I have had previously opened tubes last 2 years!

Yes! I just found out that trick a few years ago!

 

[Holokai]

OK, Now that we got Caulk Talk out of the way...

I am looking forward to splashing the boat - hopefully this weekend to try out the B175HW. I will try to remember to get some screen shots.

Apologies on the caulk tangent...

What fishfinder are you pairing it with? I’m looking at a B175M later this year so your experience/screenshots will help in deciding what to pair it with.

 

[Keitha]

I bought my boat with a Furuno TzT2 with a transom mounted 525TID-TMD 50/200 transducer (see picture below) and radar, AIS, etc. That is my main unit. It also had a Garmin 840xs installed next to it, but no transducer (originally had the abandoned transducer that I cut out). This B175HW will go to the Garmin unit.
This should be a good combo. The Furuno on 200 kHz has a narrow 5* cone. The new B175HW has a 25* cone. This should give me good coverage and resolution with keeping the ability to pinpoint structure. The B175hw should also excel looking for pelagic in the open water.

 

[Keitha]

Dave, @Socalinsd
Here is the picture I referenced:
You can see where the bilge starts to level out a bit at the center-line. This leads to the hull being a bit thicker there than on the outboard portion of the hole. I had to taper the spacer to account for that in order to pull the transducer in flush on the outside. If I wasn't cutting the hole over the preexisting transducer, I would have moved it outward a bit - being mindful of the water pickup further up the hull (I think it is the pick-up for the head - yours may or may not have one).
The red pump is feed for the Bait tank.

 

[Socalinsd]

Dave, @Socalinsd
Here is the picture I referenced:
You can see where the bilge starts to level out a bit at the center-line. This leads to the hull being a bit thicker there than on the outboard portion of the hole. I had to taper the spacer to account for that in order to pull the transducer in flush on the outside. If I wasn't cutting the hole over the preexisting transducer, I would have moved it outward a bit - being mindful of the water pickup further up the hull (I think it is the pick-up for the head - yours may or may not have one).
The red pump is feed for the Bait tank.

View attachment 19196

That definitely helps thanks. Do all the gulfstreams come with with 2 factory water pickups?

 

[Keitha]

That definitely helps thanks. Do all the gulfstreams come with with 2 factory water pickups?

Not 100% sure, but likely so. the white one is raw water washdown. It goes to the hose outlet on the starboard rear of the deck. If your boat has a factory bait tank, then it will have the pick-up for that as well.
Have you looked for a build schematic on the Grady White site?
Follow this link for the Owners Manual:

https://gradywhite.blob.core.windows.net/media/21832/2005-232.pdf

This is for a 2005

 

[efx]

Thanks for this detailed write up, even with the caulk tangent! I am about to do this exact same install with the same transducer on my 268.

it seems that the arbor of the hole saw just goes into the old transducer and acts a guide? Is this correct?

 

[Keitha]

Thanks for this detailed write up, even with the caulk tangent! I am about to do this exact same install with the same transducer on my 268.

it seems that the arbor of the hole saw just goes into the old transducer and acts a guide? Is this correct?

No, I took the arbor out when I actually made the cut (just had it back in during the picture). The old transducer kept the saw centered enough.
If you feel like you need the arbor, you can set it shallow and just use it to get started. Then once you get a cut going in the fiberglass, remove the arbor and finish your cut.

Wear gloves and long sleeves, glasses and a face mask - that fiberglass gets everywhere.

 

[glacierbaze]

That is the roomiest bilge I have seen on a GW, even if you have to remove a deck hatch to get to it!

 

[Keitha]

That is the roomiest bilge I have seen on a GW, even if you have to remove a deck hatch to get to it!

So true. It amazes me they didn't design some ample under-deck storage boxes instead of all this dead space.