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patricksher
Deckhand

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USA
13 Posts

Initially Posted - 05/06/2016 : 09:35:24

HI,
I was wondering if a transom mount transducer for GPS/FISHFINDER will work on my 1985 CAT 25 OR do I have to install a thru Hull for it? If I have to install a thru hull, where is it best to place it?
Thank you

offshoreaccount
1st Mate

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USA
71 Posts

Response Posted - 05/06/2016 : 10:52:23

you can install an in hull transducer. I have mine under the forward berth. to clarify, I have one epoxied to the hull. no holes required.

Offshore Account, 1977 Hull #243. SR, SK

Edited by - offshoreaccount on 05/06/2016 11:22:42

patricksher
Deckhand

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USA
13 Posts

Response Posted - 05/06/2016 : 11:00:09

But do i have to use a thru hull or will a transom mount transducer work?

DavidBuoy
Admiral

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707 Posts

Response Posted - 05/06/2016 : 11:29:54

quote:
Originally posted by patricksher

But do i have to use a thru hull or will a transom mount transducer work?

You don't have to use either as Offshore stated. An in-hull transducer beams through the hull and does not require a through-hull. Problem with a transom mount is that the healing of a sailboat makes placement difficult and because your keel will hit bottom before the transducer recognizes it. Problem with a through-hull is, well you need to cut open your boat under the waterline which most people try to avoid if possible.

Captain Rob & Admiral Alyson
"David Buoy"-1985 C25 SK/SR #5053

offshoreaccount
1st Mate

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USA
71 Posts

Response Posted - 05/06/2016 : 12:06:50

^ What he said.
Transom heeling can cause issues with the transducer out of the water. Additionally, running that wire cannot be done in a clean manner without adding a hole to the transom.

I've got a hawkeye D10D that I just mounted under the forward berth. Use slow cure epoxy and try to avoid bubbles in the epoxy. I tested it before epoxying by putting a bag of water around the transducer and holding it against the hull. Works pretty well, but it's a simple setup.

Offshore Account, 1977 Hull #243. SR, SK

islander
Master Marine Consultant

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3993 Posts

Response Posted - 05/06/2016 : 12:55:18

As the others said a transom mount will pull out of the water when the boat heels over. You can mount a transducer to the inside of the hull with epoxy or you can use a wax ring that is used for toilet bowls in your house and imbed the transducer into the wax. The key is to not have any air bubbles in the epoxy or wax.

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 05/06/2016 : 15:26:33

That's exactly how I have my in-hull transducer (which began life as a transom mount) mounted after my through hull transducer failed a while back. I have a 4" piece of PVC pipe that the transducer sits in, with a blob of toilet wax. I seated it and then heated the wax with a heat gun to make sure any air pockets were gone. I also dropped the temperature sensor into the same PVC enclosure and I get "water" temperature. Admittedly the temperature is a bit biased because the sensor's actually inside the boat, but since it's in reasonably close proximity to the hull and completely submerged in the wax, I figure it's pretty close, and it agrees reasonably well with my Kestrel when I dip it in the water.

David
C-250 Mainsheet Editor

Sirius Lepak
1997 C-250 WK TR #271 --Seattle area Port Captain --

glivs
Admiral

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USA
822 Posts

Response Posted - 05/06/2016 : 15:36:13

Reaching here, but if you are also asking what type of transducer to mount as an in-hull transducer you have heard the options. An in-hull transducer is optimally designed for the purpose but are notably more costly. In some situations a transom mount transducer can also be used if mounted such that there are no air pockets between the transducer and the hull. The issue is that some attenuation and possible distortion will occur as the signal passes (twice) through the hull. How the software handles such a signal will determine its accuracy. Always test whether a transducer will function before "permanently" mounting it. That said, however, I do not know how the new multi-frequency, CHIRP, imaging, directional,... transducers function outside of their design criteria, i.e. whether a transom mounted unit could function as an in-hull unit. Hopefully others here will identify the models they have used. It also wouldn't hurt to ask the manufacturer their opinion. ... If you do, let us know.

Gerry & Leslie; Malletts Bay, VT
"Great Escape" 1989 C-25 SR/WK #5972

Edited by - glivs on 05/06/2016 15:39:20

offshoreaccount
1st Mate

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71 Posts

Response Posted - 05/06/2016 : 16:27:45

so the hawkeye I mentioned specifies that you can mount it in hull. I imagine most transducer style mounts can function in a similar manner.

Offshore Account, 1977 Hull #243. SR, SK

patricksher
Deckhand

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USA
13 Posts

Response Posted - 05/06/2016 : 16:49:48

So, I have called Raymarine and they said there DRAGON FLY series transom mount will not work "in-hull". It needs to use a thru hull transducer which they do sell ($399). I'm not reaaly pumped on putting a hole through the boat or spending the $399:(

bigelowp
Master Marine Consultant

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USA
1736 Posts

Response Posted - 05/06/2016 : 17:41:50

Save yourself the agony of cleaning and maintaining a through hull or transom mounted transducer -- if you epoxy in-hull (or use silicone as I have) it will work and be easier to manage.

Peter Bigelow
C-25 TR/FK #2092 Limerick
Rowayton, Ct
Port Captain: Rowayton/Norwalk/Darien CT

islander
Master Marine Consultant

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USA
3993 Posts

Response Posted - 05/06/2016 : 18:08:34

Patrick, What is the model depth sounder we are talking about. Might help in finding a transducer that is comparable and will shoot through the hull.

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

Stinkpotter
Master Marine Consultant

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Djibouti
9014 Posts

Response Posted - 05/07/2016 : 09:36:40

I wouldn't use epoxy--you might want to replace the transducer some day... A popular in-hull method uses toilet wax--the main requirement being no air bubbles between the transducer and the hull. You can knead it into a ball, make a wax "dome" on the bottom, and press the transducer down on it so any air escapes to the sides. As mentioned, this eliminates the problems with growth and the limited effectiveness of the special anti-fouling paint for transducers. I once found that the wire from my transom-mounted transducer was cut as if with a wire-cutter, I'm guessing by a blue crab or snapping turtle. Maybe somebody didn't like the pings...

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

Edited by - Stinkpotter on 05/07/2016 09:38:48

Sailynn
Navigator

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USA
178 Posts

Response Posted - 05/07/2016 : 20:15:30

did you already purchase the Raymarine or just called them to inquire? I prefer the depth sensor to be forward to get a low depth alarm sooner than later.

Lynn Buchanan
1988 C25 SR/WK #5777
Sailynn
Nevada City, CA

offshoreaccount
1st Mate

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USA
71 Posts

Response Posted - 05/08/2016 : 18:53:11

Epoxy isn't exactly permanent. A wooden block next to the transducer and a mallet will get rid of it. Can't say the transducer will be reused, but if you're removing it there's probably a reason.

Offshore Account, 1977 Hull #243. SR, SK

patricksher
Deckhand

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USA
13 Posts

Response Posted - 05/09/2016 : 05:53:08

I already purchased it and then called RAYMARINE. Its a RAYMARINE DRAGON FLY PRO 7. I just wanted to have a combo unit GPS/DEPTH/SPEED/TEMP all in one. Does anyone know of a similar unit that is able to be installed with an in-hull?

Dave5041
Former Mainsheet Editor

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3754 Posts

Response Posted - 05/09/2016 : 16:21:33

You won't get temp shooting through the hull if that matters to you. You can also epoxy a tube to the hull, drop in the transducer, fill with mineral oil and add a spring or soft foam inside the top to hold it down, but toilet wax is reliable, easy, and removable. I used it on my last boat and never touched it after installation. With the boat in the water, you can also make a clay ring, fill it with water and put the transducer in it to see if it works. Sometimes you have to move it around to find a good spot. The company might be honest about it not working, but the clay ring and water is an easy test.

Dave B. aboard Pearl
1982 TR/SK/Trad. #3399
Lake Erie/Florida Panhandle

OLarryR
Master Marine Consultant

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USA
3368 Posts

Response Posted - 05/10/2016 : 03:08:16

Toilet bowl wax ring has worked fine for over 10 years for me.

Larry
'89 Robin's Nest#5820, Potomac River/Quantico, Va
http://catalina25.homestead.com/olarryr.html

patricksher
Deckhand

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USA
13 Posts

Response Posted - 05/10/2016 : 03:33:41

hey Larry,
where is that placed?

Sam001
Vice Commodore

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USA
441 Posts

Response Posted - 05/10/2016 : 07:01:25

Mine is located under the forward v-berth and works fine. Used Garmin mount with wires running along hull.

Capt Sam, USCG Master Near Coastal
Isle of Hope, GA. Charleston,SC. Lake Murray, SC.
Aboard Bobbin - 1982 Standard Rig-Swing Keel #2963 Dinette Model
"On a powerboat you are going somewhere....On a Sailboat you are Already There!" Capt Sam

http://my.boatus.com//memberPhotos/6315398_1_25502.jpg

OLarryR
Master Marine Consultant

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USA
3368 Posts

Response Posted - 05/10/2016 : 20:02:19

It's located under the vberth, port side. Photo is thru the opening in front of the VBerth.

On my website, you can see the transducer/wax ring glob looking down with VBerth covers removed - Check addl photos/details on my website for "VBerth Hull Fittings Enclosure and Storage Shelf" photos/details.

Larry
'89 Robin's Nest#5820, Potomac River/Quantico, Va
http://catalina25.homestead.com/olarryr.html

Edited by - OLarryR on 05/11/2016 03:40:37

Voyager
Master Marine Consultant

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USA
5232 Posts

Response Posted - 05/10/2016 : 20:41:42

I have a Hawkeye which I placed in the quarterberth well just behind the cabin. I mounted it directly inside the hull using a wax ring.
HMine straddles the fin keel and shoots more or less directly downwards, whether on a port or starboard tack.
Since I rarely sail in shallow waters I actually don't care about heel: I'm usually motoring in the shallowest areas. My depth meter, after some minor adjustment, reads about "true".

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

islander
Master Marine Consultant

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USA
3993 Posts

Response Posted - 05/11/2016 : 04:03:24

It really does not matter if the transducer is placed forward or aft. Some might think that having it forward will somehow give them advanced warning of shallow conditions. I don't know of anyone that can stop their boat in 1-2ft. If you want to know the depth ahead get a chartplotter. Find a good spot that gets a good reading and shoots somewhat straight down. I have a thru-hull mounted behind the cabin steps slightly to starboard.

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

OLarryR
Master Marine Consultant

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USA
3368 Posts

Response Posted - 05/11/2016 : 09:34:53

Agree with Scott. Also, I believe my rudder is lower than my wing keel...but not by much...maybe a few inches.

Actually, we could get into a semi-related debate/discussion regarding the merits of how you setup the depth readings on the display. For example, I believe my transducer/fishfinder are reading accurately but since my in-hull transducer is mounted below the waterline, when it reads 4', I am probably closer to 4' 6" as a comparison to the draft of my boat (2' 11"). I could adjust my fishfinder to read accurate (to compare to boat draft) taking into account the transducer below the waterline but I feel that leaving it as is gives me a conservative reading, keeps me out of trouble sometimes when I probably should have tacked or altered course already and also for those times when the depth change caught me off guard by not checking the display frequently enough. The other thing is that while my fishfinder shows the depth curve on a graph, the digital readout only reads in feet and not feet & inches. So, when my fishfinder displays digitally changing from 5' to 4' and back again, it generally means that I was not in 4' of water but more like 4' 10" or 4' 11". Looking at the depth curve on the fishfinder and the feet listed on the Y-axis, you can eyeball the depth as being more like 4' 10" or 4' 11" versus 4'. Then again, I am probably about 6" on the safe side since the transducer is mounted below the waterline.

I believe the fishfinder or all fishfinders, you can set them up to alarm at certain depths. Then I could readjust my fishfinder to read the true depth based on the depth the transducer is mounted and then alarm to whatever conservative depth desired for a warning. But I would rather just have the fishfinder be off about 6" on the conservative side.

The concern I always have river sailing is what if there is a log, etc laying on the bottom (or worse than that...a shopping cart !!). I sail a lot but do not recall except for perhaps one time that I was surprised by something under the water but was not an issue other than getting startled. Most times, it is the floating debris that I do not spot that may bite me every so often. The sound of it hitting the boat turns out to be more bark than bite. For an underwater obstacle, it is a rare possibility but definitely minimized if not regularly flirting with sailing or motoring in waters approaching the boat's draft.

Larry
'89 Robin's Nest#5820, Potomac River/Quantico, Va
http://catalina25.homestead.com/olarryr.html

Edited by - OLarryR on 05/11/2016 09:43:49

Akenumber
Navigator

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USA
247 Posts

Response Posted - 05/16/2016 : 17:01:50

I have a lowrance transom mount in the v birth. Works great until I get in 100 ft plus water and it starts to glitch. I used polyester resin and I think the wax ring might have worked better. I do get water temp, but not all that accurate.

Ken
San Diego
84 C25 SR/FK 4116
The KRAKEN

islander
Master Marine Consultant

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USA
3993 Posts

Response Posted - 05/16/2016 : 17:26:49

Works great until I get in 100 ft plus water and it starts to glitch.
Ha, Over 100 ft it would be fine if it just said plenty. Shooting through the hull probably takes away some performance.

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

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