In-hull or through-hull transducers

[Beckytek]

I just bought a Standard Horizon CPV 350 GPS with fishfinder and it came with a in hull transducer. I will call the supplier tomorrow to exchange it for a through hull model. Has anybody out there used the in hull units? If so what is your opinion about how they work. I'm afraid it won't work as well due to shooting through 3/4 in. solid fiberglass. Just curious. Ron

 

[J's Dream]

Try it and find out. Go to Toys R Us, Walmart, whatever...and get a can of Play-Doh. Mold it around the transducer where you would epoxy it into place, hook it up to the display and see how it reads.

Just know that with in hull transducers, water speed cannot be measured, and water temp will be hull temp, which does not vary as rapidly as the water will.

Jason

 

[Tim Powell]

Try it and find out. Go to Toys R Us, Walmart, whatever...and get a can of Play-Doh. Mold it around the transducer where you would epoxy it into place, hook it up to the display and see how it reads.

Just know that with in hull transducers, water speed cannot be measured, and water temp will be hull temp, which does not vary as rapidly as the water will.

Jason

If you are fish hunting throw away the in hull Tim

 

[Genesis]

In-hull transducers work ok but there is a HUGE difference with a good through-hull.

 

[J's Dream]

If you are fish hunting throw away the in hull Tim

Seeing as though Ron has a 40DC, I dont think he's a serious offshore fisherman...at least not on that particular boat.

Having sold these for many years, in hull transducers do a satisfactory job of giving depth, nothing more. In hull transducers can easily be installed with the boat in the water, and can be used without concern until the next routine haulout is scheduled...when a bronze (NOT plastic) thru-hull can be properly installed, if needed.

Jason

 

[Beckytek]

My boat is out of the water now so it's a good time to install the through hull TD. I installed a new depth sounder 2 years ago but used the old plastic TH TD.
Every time when I really needed it, the display would go blank. The original sounder did the same thing. I think the problem might be where it was installed. Between the engine intake scoop and the toilet outlet thru hull. I don't want to take any chances this time hence the new depth sounder and TH TD.
Your right about the fishing, don't do any, but really want a good depth sounder.

What's wrong with the plastic ducer? Doesn't it work as well? There is a big difference in price.

 

[J's Dream]

What's wrong with the plastic ducer? Doesn't it work as well? There is a big difference in price.

Basically...quality. Same reason we don't use plastic thru hulls for toilet intakes, or anything, below the waterline. It is a Hatteras, after all.

What's forward of the current thru hull you're having problems with?

Does your hull have strakes/chines? Are they near the transducer?

When are you getting a blank display...only on plane?

How close are those thru hull fittings/intakes to the transducer?

Air (turbulence) will disturb the sonar signal, and leave you with a blank readout.

Even an inch too close to a source of turbulence can cause LOTS of headaches!

Jason

 

[GJH]

If you have the opportunity and budget, go with the thru hull properly mounted in a fairing block. I have, via the PO, an Airmar P79 mounted in hull that feeds my Furuno system, which includes a black box fish finder. It reads depth OK, but the difference in the fish finder function is remarkable when compared to the same system with a thru hull. You don't need to be a fisherman to get good use out of the fish finder function (not sure if your Standard set up includes that). It's on my "list" of upgrades, but not so urgent that i have got to it in the past 3 years... I'd also love to get water temp.. I get speed and back up depth via my old Data Marine system.

 

[Beckytek]

There is no particular time when the sounder goes blank. I can be on plane or at idle in calm water and it happens. The ducer is located about 3' behind the end of a strake, and between engine intake, about 10" away. I want to mount it forward about 2 feet but it will be closer to the end of the strake. I don't have many good choices since the bulkhead is just ahead. The starboard side is no good either since the A/C inlet is right behind the bulkhead. I've had this problem since I bought the boat. It came with a datamarine sounder and it worked the same way.

 

[J's Dream]

Is there any way to move it inboard to get away from the strakes?

But you're saying that it'll go blank even in calm water, not moving...is the transducer mounted to a fairing block at the proper angle down? It almost sounds like it's mounted at an angle not perpendicular to the water surface, causing the signal to not "bounce" back to the transducer.

 

[Beckytek]

It's mounted flat against hull. No fairing block. The bottom is pretty flat there, about 10 degrees north of horizon. It even goes blank in water that is only 5 to 10 feet deep sometimes.

 

[J's Dream]

I think that may be the problem.

Picture yourself bouncing a tennis ball straight down on the ground in front of you. It'll return to your hand (like the sonar signal to the trandsucer). Bounce it at an angle away from you, and it's lost.

While you're out of the water, I would seriously look into a fairing block...may save you more headaches!!!

 

[Beckytek]

The fairing block looks like the way to go.
I was just looking at the instructions for installing and they say not to use the in-hull TD if the thickness is more than 1/2" thick. From what I've heard our hull thickness is 3/4".
I bought the black box fishfinder that goes with the system just to make sure I have a dependable sounder.
Airmar makes transducers that compensate for the deadrise of the hull without the use of a fairing block. There is one for up to 15 degrees and another up to 25 degrees. I don't know if S H offers these with there units or not. I will call them tomorrow to find out. Thanks for all your good advice. It's nice to know I can always get help here. Ron

 

[J's Dream]

Ron,

You're correct that our hulls are thick...mine is anywhere from 3/4" to 1" where i have replaced thru hull fittings.

FWIW, be sure that the transducer you order is long enough to allow for the fairing block thickness...remember a fairing block is on the outside AND inside of the hull, it can potentially add a significant amount of length to what you have now.

Keep us updated as to the transducer options, and your results once you're back in the water!

Jason

 

[Craig]

Through hull transducers do work, how well they work seems to be perception of the owner. Buying a good depthfinder and using a through hull transducer is like buying the most expensive stereo you can find and hooking it up to 10 dollar speaker. When you mount any transducer it is best to keep it away from any running gear on the bottom of the boat. A fairing block gives you more area to choose from as well a having the correct angle. If you have to be inline with and fittings on the bottom, put the ducer forward of the fitting.

 

[Maynard Rupp]

Here is another consideration. We have 3 depth sounder transducers, 2 are in use. They all have fairing blocks and point straight down. Airmar makes most depth transducers. My problem, which may be seen in another post, is some type of electrolysis. Hatteras has green #6 wire on every metal part that goes through the bottom. That grounding system is impressive, to say the least. None of my 3 brass depth thru-hull transducers were grounded to that bonding system. Those transducers don't even have any means of attaching a bonding wire. Sky Cheney mentioned that his transducers have a bonding wire connected to each of them with a hase clamp to starp it to the brass extension inside the hull. I have now added a #6 green wire from a nearby bonded bolt to each transducer and clamped the bared ends of the wires to the transducers. Now they have continuity to the rest of the system.

 

[Craig]

Maynard,

There is usually a ground stud on the sounder control box, check to be sure that ground goes the the bonding system. I have seen where someone has connected this ground to the battery's negative.

 

[MikeP]

In-hull works great on my 53MY - I added one last year as a back up for the standard through hull unit. It is equally accurate at all depths that I have been in - admittedly not more than 90 ft or thereabouts in the Ches Bay. I suspect that, as noted, it will not do fish finding very well or perhaps bottom profile but if you are just looking for depth readings, the in hull transducer and Raytheon ST-40 display is perfect.

 

[Beckytek]

I just talked to the factory technician. He said the transducer I will be using does not need a fairing block if the deadrise is 20 degrees or less. It must have a wide dispersement angle.

 

[Maynard Rupp]

Maynard,

There is usually a ground stud on the sounder control box, check to be sure that ground goes the the bonding system. I have seen where someone has connected this ground to the battery's negative.

My primary transducer goes to my Navman fish finder/ fuel data machine. There is no ground stud there. I was looking at a Garmin sounder module for our 4210 unit. I didn't see a stud for grounding there either. I stuck my head under to look for one on my datamarine digital unit and I don't find one there either. I am happy for Sky's suggestion as every piece of metal on this boat all goes to ground, I hope!