Moderated Discussion Areas
  ContinuousWave: Whaler Performance
  Thru-hull vs Transom Mount SONAR transducers

Post New Topic  Post Reply
search | FAQ | profile | register | author help

Author Topic:   Thru-hull vs Transom Mount SONAR transducers
Eagleman posted 11-25-2002 02:10 PM ET (US)   Profile for Eagleman   Send Email to Eagleman  
I plan on installing a Furuno Depth and Temp gauge on our 25' W/T Revenge. Currently the boat a has a transom mounted sensor for a disfunctionally depth/temp gauge. I do trailer our boat on a bunk trailer with center roller's. If I decide to go with a thru hull sensor I should have plenty of clearance. Would appreciate you thoughts!
captbone posted 11-25-2002 02:23 PM ET (US)     Profile for captbone  Send Email to captbone     
I would NEVER drill that big of a hole in any hull below the waterline! That is a big risk, plus the benefit is not really worth it. Transom mounted transducer work fine.
JBCornwell posted 11-25-2002 03:06 PM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
Agreed. Thru-hull and Whaler are incompatible.

A correctly mounted transom transducer will do anything any thru-hull will do.

Red sky at night. . .

captbone posted 11-25-2002 03:39 PM ET (US)     Profile for captbone  Send Email to captbone     
The best idea i saw is to mount a small section of starboard (or the same.) And then mount all the transducers on that. This way, you can put as many transducers as you want and only have 2 holes in the hull itself and you can also change them very easily. They way technology is, in 5 years you will want the new fishfinder anyway. Plus transom mounted transducer are alot cheaper then bronze thru hull transducers. I would only install a bronze thru hull if I i to use a thru hull! just my .02$
OutrageMan posted 11-25-2002 06:38 PM ET (US)     Profile for OutrageMan  Send Email to OutrageMan     

First off, do you mean "shoot through" or a true through the hull transducer?

My 22 Outrage had the latter, and it was no probem except when it came time to upgrade the sounder. The old transducer was not compatible with any current sounder.

If you get the transom mount, it should be mounted between the engines. You will also need to order the extension cable. 25' was about 2 feet too short for my 22.

If I were to do it over again (and I did this last year with the rescue boat) I would not rule out a through hull trnasducer. However, beacause of Village budget restraints we went with the transom mount. It was going to be about $750 for Yacht Works to glass in the transducer.


dfmcintyre posted 11-25-2002 07:10 PM ET (US)     Profile for dfmcintyre  Send Email to dfmcintyre     
..."Thru-hull and Whaler are incompatible".

If that's the case, then why did the factory have a section of wood molded in the hull to accomodate one? I'm talking specifically about early 80's, maybe later ones too.

It's located to the left of center, up forward. To access it, the cover that covers the forward bilge area (it's the one that is about 3-4"? deep) needs to be opened up (probably pretty dirty in there). From what I recall, the area I'm talking about is towards the (looking aft now) in the rear right corner of the bilge.

We mounted one there. Worked "ok". At speed it would have a tendency to lose effectiveness and made an odd noise, when the surface of the water was hitting at the right ange against the mounting block (oh, did I mention that you need to fabricate a mounting block for the correct angle? Make it out of epoxyed mahogany) Nice thing about it way up forward, was at dead idle, we'd spot things before it got challenging.


Fishcop posted 11-26-2002 12:16 AM ET (US)     Profile for Fishcop  Send Email to Fishcop     
I have a Furuno thru hull on my 25OR. Glassed in by the previous owner on the keel and no problems. On my 1977 19'OR, I had a Furuno "shoot-thru" and worked fine.
My other whalers had transom mounted transducers and they also worked fine.
Just my two cents.
lhg posted 11-27-2002 01:13 AM ET (US)     Profile for lhg    
From the Outrage/Revenge Owners Manual, second generation boats, 18-25':

"Depth finders will work at high speeds serving the function of continuously recording depths and aiding navigation. On 18', 20' and 22' models, transom mounted transducers MUST be used on Outboard, Sea Drive and I/O models. On 25' models, there is a well or depression molded into the forward hull area for through-hull transducer installations. You will notice this area as it is covered with a separate fiberglass cover and teak access cover to a drain tube.
Because the hull will require a faring block, you will find transom mounted transducer installation easier and there will be less chance for damage with trailer operation."

Russ, I would stay with the transom mount, even though Whaler Drive presents more of a problem than normal. I use transom mount exclusively. Since I bought my boat in 1989, it has had three different depth finder/GPS units as technology changes. Drilling a hole in the hull makes no sense to me considering the short life of this equipment. Nor can a speed wheel/temp sender be through hull mounted. These transducers can also go bad, then what?

I would not bother with a depth temp GAUGE. They are mostly obsolete. Get a good fish finder unit (even if you do not fish!) that has all three digital functions (speed, temp, depth) built in, and charts the bottom for you also.

bdb posted 11-27-2002 10:34 AM ET (US)     Profile for bdb  Send Email to bdb     

Whaler drive poses some mounting problems for transducers. The water passing across the stern of the WD is awfully "dirty." You'll probably find that you need to snake the cable between the drive and transom, and mount the transducer to the transom, not the drive. It's a devil, but can be done.

Eagleman posted 11-27-2002 02:03 PM ET (US)     Profile for Eagleman  Send Email to Eagleman     
Thanks for all the input- I decided to stay with a transom mount style sensor and get a good fish finder unit.Currently my old sensor is mounted on the transom I will replace new sensor in same position. Thanks again.
Everyone have a nice Thanksgiving.

Morocco posted 12-03-2002 01:20 AM ET (US)     Profile for Morocco  Send Email to Morocco     
LHG --

When I replaced my drain tubes on my 25-Revenge, there was still about an inch of foam between the layers at the tube in the covered well [cockpit sump?]. Is there a particular place in that area where a thru hull should go, based on your manual? I'm about to put in a new fishfinder and since I keep my boat in the water, I'd like to avoid hauling it out just to screw in a transom mount.

jimh posted 12-10-2002 01:41 PM ET (US)     Profile for jimh  Send Email to jimh     
Added link to this thread in REFERENCE section article on this subject. See:

lhg posted 12-10-2002 03:36 PM ET (US)     Profile for lhg    
Morocco - The only information I have on thru hull mounting in a 25 is quoted above. I use transom mounting on my 25, since I also have a speed/temp sender.
Sal DiMercurio posted 12-10-2002 05:39 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Guys, theres a simple rule to follow.
Inboards "MUST" have either a through hull, or a shoot through, keep in mind, you wont get a speed reading with either of the above, & speed can be very crucial while trolling for tuna or stripers..
Outboards use transom mounted transducers.
Transducers do not do well when mounted up front, as air breaks the reading while traveling at speed.
The water at the transom of an inboard is full of air, thus a transom mount will not work correctly.
My new Furuno LS6100 with transom mount reads the same [ perfect ] at 2 mph or 60 mph.
It is very crucial to mount a transom mounted transducer, at least 1/4" below the bottom of the boat, or you will loose bottom as soon as you get on plane.
captbone posted 12-11-2002 11:11 AM ET (US)     Profile for captbone  Send Email to captbone     
you have a straight inboard that does 60mph?
jimh posted 12-11-2002 02:24 PM ET (US)     Profile for jimh  Send Email to jimh     
Sal's demarcation of inboard and outboard style transducers has more to do with the location of the propeller and the prop wash in relation to the transducer.

As long as the transducer is in front of the propeller and clear of any prop wash, you can anticipate good results.

Sal DiMercurio posted 12-11-2002 06:30 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
No, I have a 1980 .... V-20' .. Outrage, thats 50 hp over recommended.
She's recommended at 175 hp max, & my 2000 ...200 hp Evinrude FICHT is putting out 222 hp at the prop.
I know because it was a test engine for OMC, had 13 hours on it when I got it, been torn down 4 times to check for wear.
The boat runs [ on 1 ft chop ] 60.8 mph on police radar,....3 runs, 60.3...60.8...60.3
With a 14.25 x 21 Stiletto at 59 & 6,000 rpms, jacked up on the 3rd hole, no load to speak of, just me, a 30 lb anchor & maybe 7 gallons of fuel.
She dosen't like smooth water at all, only runs 54 - 56 mph at wot, but get some air under her on a nice cool day & she picks up 5 - 8 mph easy.
Guts posted 12-13-2002 09:21 PM ET (US)     Profile for Guts  Send Email to Guts     
Go on do it! I did! and I also have a transum mount,also. The thru hull WILL WORK BETTER! now with that said. the b.s. about cutting holes in the hull, it's not all that hard to do. In fact furuno (or airmar)sends the how to do cored hulls with there ducers.
why do I have two ducers? I think some of you know me. I have a (montauk17)and I fish bottom. some thimes 200 fm. useing a 582L/
& 1850DF..(fruno)... I added the 1850DF after the 582L with the(F) modle I wanted to try the diffrence so I added the transun ducer. to the chart plotter. now I can use eather ducer on eather machine/and I have changed the ducers on thr 582L and THE thru hull WILL give a better picture! hands down.
now they say that you can not use two machines at the same time? I have used them at the same time and with NO feed back to the machine(582L) I do know what the feed back looks like as I have seen it from other boats crusing by, it is very destinc(S/P)on the screen.(curved waves on screen) in closing I think it depends on what are you or what type of fishing?
I'm VERY HAPPY with my thru hull. The only way to go, for me. as far as the traler I use a shorlander,not a problem. I have sent Jim H some pics. but I think he dose not like the idea of a thru hull in a BW or at least a small BWer

jimh posted 12-14-2002 12:04 AM ET (US)     Profile for jimh  Send Email to jimh     
Guts--by the way, don't ever name any of your kids "Fish"--it is not that I don't like thru-hull transducers or I refuse to publish your picture. It is more a case of finding the proper time and place, and writing an article to wrap around it so that people could comprehend what they are looking at.

There are about 600 pictures in the CETACEA section of the website. There are several hundred more in the Refence section, too.

In the SAIL-LOGS sections there are hundred more pictures. Probably in total on the website there are over 1,000 pictures published. Please enjoy a few of these while we wait for a chance to publish yours.

By the way, what was the name or email address you used when you sent me this image? I have had my dual-processor workstation searching the 80-GB hard drive looking for any files with "guts" in them, but they have failed to turn up anything with a picture of a transducer.

It might be simpler if you resent me the picture.

Guts posted 12-18-2002 09:42 PM ET (US)     Profile for Guts  Send Email to Guts     
jimh my user name was (montauk17) my name is Kim S.I live in san diego ca. I sent you the pics. in late 1998 or maybe 1999. I know that you have a lot of things sent to you, as I have been watching this board I have seen one to three people ask about THRU HULL ducers in montauk17 boats. almost every year, as I started in the the forum from Boston Whaler in 1997. now I have seen on this board coments (s/p) that a thru hull dose not leave much room in the tunel /bilge.well it dose work for me, useing a rule 500 model25D.also in the tunel/bilge the wires for the 2000 suzukiDF70 wires for the auto pilot ruder feed back,the hyd. steering (hoses)and other wires that run the lights and bilge pump and a THRU hull ducer and a transum ducer. It dose all fit! and works fine for me. in 2001 I logged 250hrs for the year,and no problems puting in the transum plug!

now with that said, if some one wants to put a thru hull in a montauk17 I say DO IT! BUT why??? well if you want to get the best from the machine(thats what we called them when I fished for a liveing)a thru hull is the best way to GO. what I see when I talk to other fishremen (sport)most of them do not know what they are looking at.I used a furuno paper graff. and to this day I still like a paper graff. but the times thay are a changeing, and not haveing to buy paper and the cost is comming down for the high power machines, makes the the tec.factor a biggie.
lets here it for the high power machines/ thats is why you would want to put in a thru hull is the best reed for a sounder.

I have a lot of pics. of the install if you want to post them / with coments.of how to do this. as I have see it some people might want to do this as it dose come up from time to time. if you want the pics.? I can send them after I chang my (ISP) which I'm doing now. now how do I keep my screen name (Guts) with my new (ISP)? mabe you can E/M me.
what is with the nameing of my kids? have to do with thru hull ducers???

respectfully Guts
jimh posted 11-25-2002 11:37 PM ET (US)
Ken sent me an eMail reply stating he was looking for just a depth sounder, but would buy a fish finder if "not too costly."
Actually, most of the fish finders cost less than a plain depth sounder. I like the look of the NAVMAN depth sounders, but they are more expensive than a modest fish finder.

Again, I have not seen, heard, or read of anything that would cause me to change my advice about how to mount the transducer on the transom, as reflected in my article cited above.

Guts posted 12-18-2002 10:12 PM ET (US)     Profile for Guts  Send Email to Guts     

I think I am the only one that has put a thru hull transducer in a montauk17? if some one has a thru hull transducer in a montauk I would like to see a pic. or please post/ how did you do it.

jimh posted 12-18-2002 11:47 PM ET (US)     Profile for jimh  Send Email to jimh     
I located some pics from a "KIM" [Not Kim C.] whose email name was "Montauk18" [Not Montauk 17]. I guess these must be the ones you are referring to; they were sent from an account at WEB-TV back in June of 1999.

The only comments or explanation accompanying the pictures was:

"fell free to use these pics. as nessary."

The pictures were sent in a rather unusual coding format, which was difficult for me at the time to decode. I had to open your email messsage with a text editor, cut out the base64 encoding of the attachments, and then convert them manually to graphic files. I worked quite a while trying to decode them.

I finally got them all decoded just this evening.

From the photograph (that I assume) shows the underwater portion of the transducer which is mounted on the keel center line and protrudes about 4-6 inches below the keel, I have to conclude that installation like this completely destroys any possibility of using the recommended keel roller trailer.

The transducer would be damage by the keel rollers since it protrudes so far beneath the the keel of the boat. Is that a correct interpretation of that photo?

jimh posted 12-18-2002 11:51 PM ET (US)     Profile for jimh  Send Email to jimh     
And about the naming of the children: an attempt at humor...which failed.

How about emailing me the pictures and some captions. The pictures --now that I can see them all-- look high quality. I'll be glad to post a couple of them. But send them again so I can get the latest versions, and please include some explanatory material with them.

Guts posted 12-19-2002 07:26 AM ET (US)     Profile for Guts  Send Email to Guts     
trailer I use is a shorelander with bunk typ. if a roller typ.? this might be a problem. but not for me. I can resmit(S/P)the pics. and take new ones. after the changing of my (ISP)
P.S. befor I send them I will resurch the format that you use,OK.
doobee posted 12-19-2002 08:56 PM ET (US)     Profile for doobee  Send Email to doobee     
there is NO advantage to a thru hull transducer on an outboard powered boat. you wan't to mount your transducer as deep as possible, where you have a clean flow of water. on an outboard boat that location is on the transom. with twin engines mount it dead center at the bottom. with a single engine, mount it to the left of the engine to help counter the torque from the prop. pick a spot on the transom between your trailer bunk and the outboard. if you need to, its easier to make adjustments with a transom mount transducer.

with a thru hull tansducer you will have a large fairing block hanging below the hull which may cause adverse performance such as porpoising. improper installtion can have adverse effects on the sounder's performance as well and if you don't get it right the first time, it's very hard to make adjustments.

an in hull transducer will not work unless you remove all the foam down to the outer layer of glass (easier said than done. you can not have any bubbles between the transducer and the water. if there are bubbles trapped in the outer layer of fiberglass laminate the in hull transducer will not work properly.

Guts posted 12-20-2002 08:49 AM ET (US)     Profile for Guts  Send Email to Guts     
doobe I desagree with you. now in a montauk and only a montauk, that I am talking about.
I have both a thru & transum mount ducers. when the transu mont is put in place of the thru hull in stoped water (so that I can say no water disturbance)(useing a Furuno 582L in over 600feet of water)the picture IS Better with a thru hull. do you have a thru hull in a montauk? with at least a 600watt(rms) machine?

what I have been trying to say, is that more than two people this year have asked about thru hull ducers. now I have done this and think I am able to say that I know what I'm talking about. but I can not spell worth a darn! as you can see.
if done wright there is no need for adjustments.
doobee posted 12-24-2002 12:53 AM ET (US)     Profile for doobee  Send Email to doobee     
guts,a transducer is just a ceramic element encased in lexan regardless of whether it is a transom mount, or thru hull. all other factors being equal, there should be no difference in performance while the boat is at rest. Transducers are designed to operate at specific frequencies and beam angles. if your transom transducer has a wider beam angle or a different frequency than your thru hull, that could account for the difference in performance. the difference in performance could also be due to some manufacturing defect, corrosion in the plug, a knick in the wire, scratched transducer, etc. if i remember correctly, your fish finder is a dual frequency model. are you using a dual freqency transducer in both cases? Does the transom mount performance change if you change frequency on the fish finder?
Guts posted 12-26-2002 11:07 PM ET (US)     Profile for Guts  Send Email to Guts     
doobee, maybe a cams br7 is a high performace ducer? I was not aware of that. but what I am saying the defination(s/p)IS better!!! with the turu hull, and will I will take some (dig.) pics. the next time I fish deep water(I have some of 180fm)I have fished deep water (commercialy) for a liveing ( for some 10 years)and I know what I'm looking at.
I would compair your facts as someone that is looking at specifications rather than useing this product. and I have done the test on the ducers. on 50kHz/ zoom...

so say what you want! I saying to you haven't done what I have done.

there are no nicks in the wires or any thing wrong with the wireing,I do all the work on my boat myself. so I know that there is done right.
with respect,

doobee posted 12-29-2002 09:00 PM ET (US)     Profile for doobee  Send Email to doobee     
all i'm saying is that there has to be something about your transom mount that causes it to behave differently.

i remember an electronics dealer that advertised that they custom tuned each fishfinder to match the transducer. i don't know if there's any merit to it, but perhaps that is where the difference lies.

otherwise i'd say your transom mount is either defective, or it's the wrong frequency.

jimh posted 12-29-2002 11:12 PM ET (US)     Profile for jimh  Send Email to jimh     
Many years ago I worked for an instrumentation company which made ultrasonic flaw detectors, a device remarkably similar to a fish finder in its operation. Our instruments cost upwards of ten thousand dollars (in 1972) and performed at the limits of sensitivity as dictated by the laws of physics.

We did not custom match our transducers to individual instruments.

Post New Topic  Post Reply
Hop to:

Contact Us | RETURN to ContinuousWave Top Page

Powered by: Ultimate Bulletin Board, Freeware Version 2000
Purchase our Licensed Version- which adds many more features!
© Infopop Corporation (formerly Madrona Park, Inc.), 1998 - 2000.