Transducer - Inside or outside fibreglass boat?

[hardworking]

Hey Guys,

I have just purchased a Lowrance HDS7 Gen2 with an 83/200khz transducer, and am would like to know your recommendations about mounting it inside, or outside of the hull.

I have a Searay 180 Glass boat, and I have done a bit of research, but there equally confusing arguments on both in or out, so wanted to know if any of you have a real world experience you can share.

Any advice is very much appreciated.

Cheers
John

[wardy40]

John I have a HDS7 & 10. I originally had my transducer mounted with silastic in the bilge area. Work faultlessly and worked excellent at speed. No worries about it getting hit and broken.
Now my transducer is out on the transom. Not ideal, but due to mounting the structure scan transducer under the hull in the centre line at the transom, I had to relocate the normal transducer.
So for peace of mind and great sounder readings at speed (only if the hull structure is sound and no air gaps in the layers) in hull is the way to go for me.

Cheers



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[scottar]

Both installation methods have their benefits. Inside - no chance of damage when trailering or from contact with objects/people , no issues with fouling on boats permanently in the water, no holes in the transom, typically (not always) less problems with working at speed. Outside - better performance as a fish finder due to no reduction in signal levels (the amount of signal loss is virtually impossible to predict due to variations within hulls), will work on any hull type dependant on turbulence. The best install really comes down to your usage and the boat. Personally on something like a Searay, provided the hull is solid glass (no foam layer or internal moulded liner blocking the signal) and you don't intend offshore fishing, I would go with an internal installation in a wet box to start with. You can always move it outside then if you are not happy

[airlock]

Mounted correctly i would say outside, i have tried both and got a clearer picture of the bottom with less static on the picture. It's also a lot less hassle to mount and wire it up to the back.

[MyWay]

is it inboard or outboard ?

[TheRealPoMo]

I have a Reinell 185 so would be similar to your Searay. Transducer is in the bilge just in front of the engine embedded in silastic. Reliable depth reading at any speed but possibly lacks definition. ..or maybe I just can't find fish...
That said, I see what I think are baitballs in 40 feet crossing Moreton Bay at 26 knots.
I have been tempted to mount a second one on the back for more detailed info but not that committed to filling the esky with fish...which is probably a good thing given my record so far.

[scottar]

Silicon mounting will work. It works better with some transducer designs than others. Thing is though, it's a bit like fitting a set of ear muffs to your transducer. Try filling your ears with the stuff (no, please don't do that) and see how it effect's your hearing. Lowrance transducers due to their shape (curved, not flat) lose a good portion of their signal due to the silicon not being able to be thin apart from under the very bottom of the transducer. A wetbox, while being a bit more work to set up, does not suffer from the same issue. The easiest way to "make" a wetbox short of buying the transducer that has one incorporated I have found, is with a poly pipe fitting and screw on end cap. A through hull transducer installs into this very easily. A transom mount takes a bit more work but is still not difficult. Just cut the end of the fitting to match the hull angle so the transducer ends up at the right angle, rough up the poly to help the sika stick, clean the hull and seal/glue it in with sikaflex. Once the sika is dry, fill with water, fit the lid/transducer assembly and you are away. You can use other fluids in the box but water is cheap and there is generally plenty of it about when you are using your boat if for what ever reason the wetbox needs a top up. A wetbox install also means that if you are not happy with the performance of your set, you don't have to try to remove the silicone from the transducer prior to transom mounting. If you do decide to try the silicone mounting method, DO NOT, use anything other than silicone. If you use sika or similar and have to move the transducer, you are in a world of pain. If you wish to see if a wetbox install will work in a chosen location, this can be done by using a thin plastic bag (shopping bags are perfect), filling with enough water to cover the transducer, put the transducer in it, wet the outside of the bag and the selected spot on the hull and place the bag/transducer there and try it. This does need to be done in the water as a sounder generally won't display much of a reading with the boat on a trailer at home. If it can be done safely (with an inboard this may be difficult) someone can hold the bag assembly while you go for a quick run to make sure the location is good at speed.

[hardworking]

Thanks guys.

The boat has a Mercruiser inboard stern drive.

Lots to think about. I am just not sure if I am comfortable drilling holes in my hull, but I am also worried that I might not get it mounted properly. :(

[terryc]

If you don't want to drill holes in the Transom fibreglass . I have found success in Sikaflexing a small timber or nylon plate to the hull then screwing the Transducer to the plate.

[hardworking]

But don't you still need to drill through for the cable?

[airlock]

If you're really not keen on the idea i would say the best thing to do is contact the manufacturer to see if they have a specific recommendation for where to mount the transducer and then pick a local marine mechanic. That way you know the job will be done right and the work guaranteed, you won't have to do any wiring witch will be a huge saving in time and blood pressure meds. shoot through hull set ups while they don'y require drilling the hull are much more work to install and fine tune, if you are'nt happy with a transducer mount i doubt you would have all that much fun dealing with this method of installation either.

you don't have to drill a hole for a cable, you can run over the transom and them under or through a hole to the gunwhal, it doesn't look as good as you do have a viable wire but it saves an extra hole that may be a point of ingress for water, its also good if you have the transducer on a bracket that slides up an down.

[scottar]

111296
But don't you still need to drill through for the cable?

On your style of boat - yes or the install will look really untidy. If you do wish to go with an external mount it looks like you will be restricted to the port side. The ladder on the starboard side will greatly increase the chances of someone using the transducer as a foothold or slipping and hitting it. From what I have seen of these style of craft, if they have a factory fitted sounder it is typically a digital gauge type display with an internal mount puck style transducer specifically designed for shoot through hull applications. As suggested, if you are that uncomfortable with the concept of putting holes in the boat, you may be better off engaging a marine professional to do the job. ( After you have drilled a few thousand holes in various boats - especially the million dollar variety, you do tend to stress a whole lot less). Even so, transducer mounting is never an exact science and performance can not be guaranteed. Even as an industry veteran, I have run into a couple of boats over the years that took extensive trial and error to get sounder performance that the client considered satisfactory.

[MyWay]

I just instaled on friends 180 Sea Ray 2007 on transom
due to shape of hull it was almost impossible to install inside with out puling a motor out .
I also did on Glastron 185 with Garmin sounder inside of the hull with out drilling holes at all .
I had to make small wet box and placed transducer inside .
reads awesome but Glastron got different shape of the hull then Sea Ray

[hardworking]

@MYWAY - I would love some more detail on your install on the SeaRay. I am not about to take it to a boat shop. I can d the job - I rebuild motorcycles and have many years in electronics. The job itself does not bother me, I just like to do the research first so I don't make a mistake that someone else may have already done.

If you can share some info on that install, I would be grateful.

Cheers
John

[MyWay]

when I see me mate I will take some photos and share it
it is easy as to do transosom instoll ,it is like any other boat
Back of Searay is not thick , and no wood at all .

[hardworking]

Thanks man! That would be great help.

[hardworking]

Myway - you don't happen to have those pics do you?? Just finished reading the instruction and it wants a 1 inch hole. That's big man!!!


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[MyWay]

here one photo I hope it will help you

sorry about photo
have to till you PC to have look

[hardworking]

Hmm. Thanks man. Is that all below the water line and was it a 1 inch hole. That's a big hole. :(


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[scottar]

Look up "clam vent". They are available in a few sizes in both plastic or stainless (looks a heap better than plastic). They will definitely be available from somewhere big enough to cover a one inch hole. Typically you would not drill your cable entry hole below the water line - that is not to say I haven't seen it done, but it is not something I would do. The clam vent is sealed with a liberal amount of sika or similar
Images for stainless steel clam vent (https://www.google.com.au/search?q=stainless+steel+clam+vent&biw=1093&bih=482&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwiqmujqiIbKAhViMaYKHcRBBrIQsAQIJw)

[hardworking]

Thank again man. I'm freaking out about drilling an inch hole in my hull.


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[scottar]

No need to freak out - measure twice drill once. Could be worse - you could be mounting a one kilowatt through hull in the bottom LOL.
Hole for that is about 4 inch:o

[hardworking]

Holy crap!!!


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[Jsmfun]

Mate I did a through hull and it's not as scary as you think I posted it on here (through hull install)

[hardworking]

So I have jumped in and started the install of my sounder into my boat. As mentioned previous, I had to mount on port side as the swim ladder on the starboard would mean it could easily get kicked. The manual states that it shouldn't be mounted on the port, but after some research, people don't seem to notice a difference. Let me know otherwise if you have. :)

After spending a considerable amount of time planning the location for the hole etc, I started the drill, and went past the point of no return. I have routed the cable "up" through the hull instead of sideways. Nice thin part of the whole, and is sure to be above the waterline. :) I still have to mount the stainless cover and seal the hole (will pick them up tomorrow)

The head unit was interesting as not really a lot of locations to mount in my boat, but I like the way it worked out! :) It tilts back for easy viewing and is out of the way where it won't get damaged. :)

[ranmar850]

I don't know if that 83/200 will have enough power to shoot thru hull. if they are the same as the 83/200 455/800 Chirp transducers fitted to the HDI-7's, they start to lose power and definition very quickly over 20 metres. Mine is mounted on the transom, and i was so disappointed with it i got an HST-WSBL 50/200 second hand, real improvement even at 20 metres, and by the time you get to 30 metres, just no comparison.

[hardworking]

That's another reason why I mounted mine outside.


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