Transducer replacement

I have a bad B744V transducer. I plan to replace it on the next haul out this month. The research I have done says it is tough to just knock out the old transducer saving the fairing block. I would really like to make this easy. It looks like it should just unbolt and knock out through the bottom. Has anyone done this? Any advice would be appreciated.

I'm pretty sure you wont see it happen that way. The B744 uses a recessed faring block in most cases & the transducer is usually glued to the block. You *might* reuse the block if it's a low speed block but if the installer used any kind of decent sealant, it'll be a bear to remove. I've never been so lucky in the 35 years I've been in the business.
Plan on cutting a new block.

boomerang said:

I'm pretty sure you wont see it happen that way. The B744 uses a recessed faring block in most cases & the transducer is usually glued to the block. You *might* reuse the block if it's a low speed block but if the installer used any kind of decent sealant, it'll be a bear to remove. I've never been so lucky in the 35 years I've been in the business.
Plan on cutting a new block.

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Well, that not encouraging. Anyone else done this. I'm just try to cut the man-hrs down. I am having the yard pull the old one and insert the new.

Isn't the B744 the removable type...with pin & chain? I thought they could be un-done within the boat and just pulled out. They came with a plug so that if you are quick/handy, you can install a plug while you get ready to re-install the new trannie. Of course if you are hauling out, even easier.

Yep, it is internally removable. Here's the tech document:

I think the speed wheel is removeable, but the depth and temp remain in the in the water part.

Aquabelle said:

Yep, it is internally removable. Here's the tech document:

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Based on the drawings it looks like it is installed from outside the hull, up through the fairing block. There is a plug that pulls out that has the speed paddle on it, but the transducer doesn't pull out. I think the problem getting it out will be based on what type of sealant they put on the transducer. IF its 5200, then the fairing block may get tore up. I read some info on using heat and special solvents on 5200.
The yard is doing the job. I just want to know what I am getting into when the cash register starts rolling at $100/hr.

I replaced my "through-the-hull" transducer with the type that simply sends its signal directly through the hull. That is, I abandoned the old one in place and the new "hockey puck" style requires no cutting or drilling. It was a Raymarine product which cost about $115. It was pretty easy to install.

My speed is now calculated via the GPS. The only downside I see is that I no longer get a water temperature reading.

It depends, but I'd bet it will be a bear.

Most installers use 5200, myself included, and that is tough to break loose. The last one I removed, I drilled the guts out of it and chipped away at the sides with a chisel until it broke loose.

There is a products called DEBOND that supposedly dissolves 5200. And at $100 an hour it may have some merit. I haven't messed with getting any yet, but next time, I think I'll try it. (have a transducer change coming up)

Of course, after you get it out there's cleanup to do with the hole and resealing so there is now possible water leaks into the hull (depending on the material).

If you're paying for labor, you sure want someone that has done it before.

So may be best to leave old in place and just install new 'ducer elsewhere?

If your MFD can handle the hockey puck, stick-on style, I think it's a good option. Mine is 2012 Raymarine E-120 Wide screen so I had to figure out which product was compatible.

There can be no voids (air) in the hull where you locate it.

Aquabelle said:

So may be best to leave old in place and just install new 'ducer elsewhere?

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Then that's another hole in the boat. I hate that!
There's pretty much labor involved in replacing the existing one with another B744V, though. They'll have to knock the old transducer & fairing block out (no easy job, especially if the nut is corroded & seized) & clean up the old sealant, cut the new block, reinstall the transducer & pull the cable back to the display.
The easiest & cheapest way is what rclarke246 did; a P79 in-hull transducer. No temperature or STW but they do a good job of picking up the bottom if your hull is a good lay-up.
One other option is to go with a flush-mount , tilted-element transducer. They'll fill the existing transducer hole & they're WAY easier to put in with no fairing block. You'll still need to put a stainless or bronze flat head or carriage bolt where the B744 anti-rotation bolt was, though (if you have a hi-speed block).

I removed one of those during my refit project. It came off in pieces and Sean was quite entertained by my efforts. Went back with one of the flush mount transducers that has the internal 20 degree offset sensor.

Think I would have a new block ready to go as the time lost trying to save the old block could quickly pay for the new one.

My boat came with 3 transducers. Replaced 2 and fiberglassed the 3 closed. Then there were the 5 seacocks I removed..........

Ted

What does is transducer going to wire to?
MFD
Gauge

I`ve one installed conventionally thru the hull,and one shooting thru the hull.(Garmin said I could run both sounders off one transducer, but no). My 1981 hull is solid 1" plus, no shoot thru pocket. Used an angled poly tube with the included transom mount transducer encased and placed level in silicone(calm down RTF) inside the tube. Takes a few seconds to find the bottom after switch on, then it`s fine.

Pgitug said:

What does is transducer going to wire to?
MFD
Gauge

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Raymarine e127 fish finder compatible.

Thanks for all the great feedback. The new b744v is on its way. I don't like the "spare it and make another hole" ideas. I am a gambler so I will this the five and hope the old unit comes out without destroying the fairing. I will let you know how it goes.

Mine was done this spring, same transducer. New transducer came with new fairing block, did not need to use it. Old one was pushed out from inside, after as much sealant was removed as was possible. Old fairing block was supported on outside to keep from separating from hull. Works fine down to 1200 or so feet.

Thanks Rebel, gives me a little hope.

Well, how did it go?

Boat gets hauled next week. I will update when done.

Sometimes you can run a piece of spectra fishing line under the fairing and cut the sealant with it, put a little handle on each end of the fishing line like a wire saw. It won't get all of the sealant but it sometimes will cut almost all of it, perhaps enough to make the removal easier. A thought...

AKDoug said:

Sometimes you can run a piece of spectra fishing line under the fairing and cut the sealant with it, put a little handle on each end of the fishing line like a wire saw. It won't get all of the sealant but it sometimes will cut almost all of it, perhaps enough to make the removal easier. A thought...

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I hope they don't have to remove the fairing.

Dave,

I've done this twice. The 1st time I installed with 5200, HUGE mistake. If you want, install the fairing with 5200, but the transducer should be bedded with polysulfide (Life-Caulk) Polysulfide cures underwater, it's not an adhesive, and it stays pliable so it makes an excellent beddding for thru-hull use. There's just no reason to use 5200 on stuff you may want to get apart as some future point.

Now, if your B744 was installed with 5200, then use this stuff to break the bond.https://www.debondcorporation.com/products/marine-formula
It's not cheap, but it WORKS. Use as directed, it will assist in breaking the bond. To remove the thru hull, I pulled the center paddle assembly and made a toggle with a piece of chain and a bolt. Use as big a chain as will fit into the hole, drop it through from the inside after removing the inside nut from the TXDCR. Then put some blocking against the hull, and use a 4x4 or suitable lever to lever the TXDCR out of the hull from the outside. The DeBond should be applied a half hour or hour ahead, use a razor knife to score the bead to allow the DeBond to enter the 5200 surface.

If you install the new TXDCR fairing with 5200 but use polysulfide on the TXDCR itself, when it comes time to replace, it'll pull right out and the fairing will remain intact.

Hope you can salvage the fairing, they are tedious to re-do.

As an aside, my luck with the speed paddles is perfect-100% they NEVER work for more than a few days.

I have had 2 of these replaced and both times it was less expensive to sawzall the ducer and fairing off the boat, clean it up and install the new part. Whatever the used ducer is worth, you will spend twice that amount in labor to save it.

This is all assuming it was bedded with 5200, which is a near certainty in my area.

Good luck with yours.

Rebel112r said:

Well, how did it go?

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SHAZAM! $170 bucks out and in! The previous install didn't use a lot of 5200. The yard boss said that won't be the case next time.

You lucky duck! Congratulations! I'm sure you can find something else onboard to spend the money you saved!

boomerang said:

You lucky duck! Congratulations! I'm sure you can find something else onboard to spend the money you saved!

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You betcha

Does not look like air airmar fairing on the outside of hull. The Transducer fits flush with fairing using the Airmar fairing. Looks good to go, though, so it worked out.