In Hull or Transom Mount Transducer?

mm289 · 17 July 2018, 22:35

So next bit of kit on the list is a Fishfinder/Chartplotter/Depth Sounder combo.

Having read a few threads including Fen's one the Garmin 45CV is looking top of the list at the moment. This is mainly due to the G2 charts included in the circa £300 whereas when you start to look at other units like the Raymarine Dragon Pro you get into very confusing waters with Navionics "Silver" charts that aren't upgradeable or you need to buy a "gold" subscription for etc etc.

Anyways, thats not the point of the post - transducers are

I have seen some people use transom mount and I know @gurnard has used an in hull fixed to the inside of his F-rib.

As I have a F-rib as well I am thinking about doing the same but just wanted to get opinions.

As I understand it from a chat with the guys at Cactus the trade off is that in hull wont give me the high definition "Clearview" that a transom mount will, but it will give me decent reading when under way whereas the transom mount will get a lot of interference......

My use case in terms of priority is:
1. Chart plotter/GPS from a safety and ease of use exploring new coastline
2. Depth sounder for said exploring of new coastline like west coast Scotland
3. Fish finder for when fishing although I expect I will be more likely to just chuck a line over the edge and try my luck

So given the above, any thoughts/advice/experience of different transducers?

Cheers,

Paul.

Orwell boy · 17 July 2018, 23:09

Speak to the garmin helpline boys ,they are very helpful ,i made a call the other day as i had bought a 6 pin transom mount tranducer but fancied trying to use it in hull so i could keep the transom mounted Lowrance dedicated depth finder as well (which was not my original plan ) the guys emailed me instructions on how to mount the transom mount in hull ,good guys

mm289 · 19 July 2018, 16:51

Thanks, will give them a call - anyone any experience of fitting either transducer type?

Cheers,

Paul.

The Gurnard · 19 July 2018, 18:28

Hi mm289.. you can try it for yourself first. Just pop the transducer in a thin plastic bag full of water. Put a little water in the rear section of your F Rib and sit the transducer in it. That way you will know if its the correct way for you before fitting it permanently in hull or fixed to the transom.

They say you loose a little depth with in Hull. Which is possibly correct however as mine .. (and its a £100 Lowrence Elite 3x ..so just a cheapy).. reads depths down to 200ft or more in my Frib. Im really only interested in shallower depths..expecially when on the plane..so I know if the seabed is getting shallower and thus give warning there may be rocks I may hit etc..

Advantage for me on the In Hull.. is its fiited now and forgotten about. Disadvantage is I have to ensure the lead that plugs into the Fishfinder is kept out the water as its obviously packed up inside the F Rib when its folded up and packed away or unpacked and getting ready.

Disadvantage for me on the transom mount ( it was transom mounted before in hull) It tended to loose all readings when on the plane despite the positions I tried. Transducer was always getting knocked when landing or packing away. It eventually snapped the mount.

For me its a no brainer..but may not suit everyone . However as mentioned in the opening paragraph.. you can try before fixing permanently and see for yourself.

jwalker · 19 July 2018, 19:26

Fix it into the hull and keep the cable plug dry. Mine is firing through a pretty thick hull and a wodge of silicone and it can see the bottom at over 500ft so I doubt you'll have a problem in your little boat. If you mount it externally, you'll forever have issues with it.

Set it into silicone sealer being sure not to have any air bubbles trapped below the transducer. Also, if you know of any part of your hull which leaves a bubbly wake, don't mount it aligned with the bubbles, pick a smooth running part of your hull.

mm289 · 19 July 2018, 20:20

Thanks guys, I am leaning towards and in hull. Seems a lot less hassle to me than a transom mount. The one I am looking at recommended by Cactus is a dedicated in hull though so could try in different positions but once I'm committed it couldn't be change to a transom mount.

As mentioned earlier, the ability to depth sound on the move is more important to me than the ultimate clarity of view when fishfinding etc so that's why I am thinking in hull.

Cheers,

Paul.

Orwell boy · 19 July 2018, 20:46

i used to sell ultrasonic flowmeters for a living and we held and tried different positions on pipes using "acoustic couplant " this was just Boots ky jelly and i have since used it for moving around my in hull sensor ,works perfect , when you are sure about the best position ,arraldite

jonp · 20 July 2018, 09:56

I've always used transome mounted transducers, I can reach 700m with a standard Lowrance tranducer 200/50 kHz. I don't start loosing bottom with 200 untill after 300m where I need to drop to low frequency 50. Depending on water conditions I can normally hold bottom at 22knots in depths of 300m, after that in need to slow the boat to hold bottom.

The Gurnard · 20 July 2018, 10:56

Quote:

Originally Posted by jonp

I've always used transome mounted transducers, I can reach 700m with a standard Lowrance tranducer 200/50 kHz. I don't start loosing bottom with 200 untill after 300m where I need to drop to low frequency 50. Depending on water conditions I can normally hold bottom at 22knots in depths of 300m, after that in need to slow the boat to hold bottom.

Hi johp .. For clarification The Lowrance elite 3x uses a standard 200/83khz transducer so has not a hope of reaching those depths.

The manual says 800ft max but in reality..sitting stationary on my transom..it lost the bottom around 350-400ft.and that is on 200khz.

I appreciate your transducer will get far better results .. but the OP or others who compare my results with yours will be mislead as we are talking different standards...and may think transom mount gives far better figures.

gpsguru · 20 July 2018, 11:11

In 40 years of owning boats I have found that 'in hull' tranducers on planing boats are very hit and miss, and experience tells me more 'miss' than 'hit' ! ....I now always stick to a transom mount, also it has the benefit of telling me the sea water temp.

Having said the above, it is also very easy to get the transom mount just in the wrong place which pick up air bubbles from under the boat ......... starboard side if the engine, on or near a lifting chine seems to be ok on most boats.

'In hull' or 'through hull' on dispalcement and semi displacement boats works great with no issues.

mm289 · 20 July 2018, 11:21

Thanks for the input - all good stuff

I think the other variable to mention is I am using it on a Frib, rather than a RIB, so like Gurnard it gets pack away after every trip. Also it is a relatively short hull length being a 3.3m Frib

That is the other thing that is leaning me towards in hull as I don't want to keep knocking or having to remove when folding up. I am also suspicious of how "clean" a view I will be able to get with the transom mount given how much noise their is behind the Frib.....

That said the transom mount does allow you to take advantage of the Clearvue on the Garmin which I don't think in hull does.

Decisions, decisions, decisions,

Cheers,

Paul.

Fenlander · 20 July 2018, 23:11

How about temp mounting the transducer on a bit of wood and first time out with it just use a G-clamp to fit to the transom and see how it works for you. That's what I did to find the best position before drilling. I have a totally satisfactory depth reading in 95% of conditions but it is in an inch or two deeper than ideal and it must cause a bit of drag.

Fenlander · 20 July 2018, 23:14

Like this...

jeffstevens763@g · 21 July 2018, 09:01

I have transom mount skimmer transducer fixed perminant but it's only one bolt to take it off just leaves the bracket works well

jonp · 21 July 2018, 16:03

Quote:

Originally Posted by The Gurnard

Hi johp .. For clarification The Lowrance elite 3x uses a standard 200/83khz transducer so has not a hope of reaching those depths.

The manual says 800ft max but in reality..sitting stationary on my transom..it lost the bottom around 350-400ft.and that is on 200khz.

I appreciate your transducer will get far better results .. but the OP or others who compare my results with yours will be mislead as we are talking different standards...and may think transom mount gives far better figures.

Thanks for the clarification but may I suggest you don't have yours set up properly. I have installed many Lowrance units on my own and other people's boats, most using the 200/83, I even have one myself.

Lowrance may state the depths you quote but I can assure you the 200/83 will do far better than you are managing, over 300m on 200 and at least 500m on 83.

Here's a couple of screen shots from an older hds 8 I owned about 6 years ago, look for yourself in the bottom of the shot to see 200khz in over 300m. Note I'm still holding a strong image of the bottom at 40kmh. The line of interference from top to bottom was after stopping and starting.

Can you show screen shots of yours dropping out at 400ft and also show where on the transome you have fixed your transducer as something doesn't sound right.

Once again sorry this isn't helpful to the op but it maybe to others or even be for you. By the way you do know that 83 is for deeper water, why were you on 200 if it was dropping out, surely you would of gone to 83 as soon as it struggled. Also the op was asking for a gps sonar unit, I wasn't aware the elite 3 you mention was a combo.

jeffstevens763@g · 21 July 2018, 18:29

Jonp I have similar set up 83/200 I usually set it on auto as it suits my needs just for info are you setting yours up in advanced mode manually?

GuyC · 21 July 2018, 19:41

I went through a similar decision process when I bought a chartplotter. I liked the idea of a through hull transducer but the deadrise on my boat is such that a large area would be in the shadow of the hull.

I couldn't justify the man maths to buy two transducers so I went for a transom mount and it seems very good. I would like to compare it against a through hull transducer though to see if there is a difference in quality.

Chris Caton · 21 July 2018, 19:42

I've got a garmin 4008 chartplotter with a in hull transducer, gives good depth readings up to +40knots, only problem I've ever had with it was the transducer came loose in the bayonet mounting once and lost the oil, just gave it a good clean up, refilled with olive oil and it's been fine since, about 10 years old now

unfortunately the chartplotter is playing up now so time for a new one, but can't complain after best part of 10 years on an open rib

The Gurnard · 21 July 2018, 20:39

Quote:

Originally Posted by jonp

Thanks for the clarification but …..

Hi Jonp.. I think that you are still trying to compare apples with oranges.

The reason I say that is the HDS 8 you have shown prints for probably has a far higher sonar signal send unit and also more sensitive receiver than the cheapo Elite 3x that I keep quoting figures to you. I believe even the fish finders are not “standard” in that respect and I have always assumed these factors affect the depth reading as well as other factors ..including differences in transducer quality and poor installation.?

Example in the Elite 3x manual..and I would suspect their quote of the max depth for the unit is more accurate than your “guess ?” for this particular unit.

Max Depth ..800ft ..power output 130watts

http://ww2.lowrance.com/Root/Lowranc...0547-001_w.pdf

Now compare that with the more expensive Elite 4x

Max Depth 1000ft or more ..power output 250watts

I presume it would also explain why some fishfinders cost over £1000 and some under £100 but if you think they are all standard and should read the same depths.. as mentioned please correct me because Im not an expert.

Quote:

Originally Posted by jonp

why were you on 200 if it was dropping out, surely you would of gone to 83 as soon as it struggled.

I quoted 200khz simply to compare it with your 200khz reading..I do appreciate 83khz goes deeper but I cant compare those figures with your Standard 50khz figures... as then I would be the one comparing apples to oranges

Quote:

Originally Posted by jonp

but may I suggest you don't have yours set up properly.

If you can convince me that all sonar send levels and sensitivity of the various models are identical.. or if they are not..at least they should all read the same depth .. then I will look into my setting up procedure ..until then..Im very happy with my setups thank you

Quote:

Originally Posted by jonp

Also the op was asking for a gps sonar unit, I wasn't aware the elite 3 you mention was a combo.

Im sorry..but I disagree on that point

..the OP was asking about transom mount or in hull mount..or thats the way I read

Quote from first post.“So given the above, any thoughts/advice/experience of different transducers?”

And I answered that … on an identical boat to his ..I preferred my in hull fitting to transom mount..because the transom mount kept bending and eventually broke off putting it in my car every other day..

Hope that helps you understand my thoughts

jeffstevens763@g · 21 July 2018, 21:57

On my rib I had both through hull and transom mount on different makes which is hard to compare both they seemed to perform well for both of them for my needs, but my take on it they must be in the same ball park or manufactures wouldn't advocate the use of both.obviously the more you pay for your unit the better performance of the unit,when I use the sonar I travel slow so resolution is very clear my target depth up to 50m I run on auto so I don't have to constantly change settings but that's me.