Transducer placement?

[ktm_2000]

Been working too much lately and need to get focused on the boat.

I purchased an airmar B175HW 1KW transducer and would like some more opinions before I cut a hole in my boat.

I am somewhat limited by a series of different requirements, Transducers recommended on starboard side of boat, the grid system of the stringers as well as where the boat rests on the trailer.

I would have a nice clean area if I could put it on the port side of the boat in the old motor well, plenty of space would be in clean water lifting strakes wise.

starboard side underneath - 11" from thru-hull to where the boat sits on the trailer, I would not want the bunk rubbing on or resting on the bunk when launching or storage.
https://photos.app.goo.gl/S2kQdS3xgBGCd5dS8

inside starboard old motor well. I have 13" of space outboard of thru-hull until it would interfear with stringer flange. I am also limited how far forward I could go due to the grind system flange.
https://photos.app.goo.gl/5kCiwTcuV2hC7ai56

questions

- is port side downsides overblown? would I be fine putting it on that side?

- if I went on starboard side and put it approximately where I put the bronze clamp, would there be a potential to get air bubbles generated from the thru-hull spraying forward over the transducer while under way?

I am kind-of stuck on that side, the further away from the thru-hull the closer it could be to the trailer bunk and I really do not want to damage the transducer going on and off the trailer or doing damage by having the weight of the boat resting on the transducer.

your thoughts ??

[CamB25]

My thoughts: no location aft of the end of the first strake works very well. Lots of turbulence. Go forward on the boat as far as possible, probably in your center console, and as close to the keel as possible.

First picture - is that a live well pickup? Go forward.

Second Picture - My B175M is mounted in roughly that location, slightly higher on the hull. Works great to 10 knots, then becomes completely aerated.

I've tried these in the old motor well area, port and starboard:

B175M - portside, midway between 1st and 2nd strake. Aeration at 10 knots. I believe a major source of turbulence is the first strake that ends way far forward. I might eliminate that strake one of these days. My bow thruster probably doesn't help: https://www.amazon.com/photos/shared/ip ... eTCcn-SfWu
x marks the location of the transducer https://www.amazon.com/photos/shared/_s ... gIjk2ykhR2
This is the return at speed when I heel over to port. Good signal when fully in the water, no good at level keel: https://www.amazon.com/photos/shared/tZ ... R7KA7NJkfv

Furuno 525STMSD fairing block - located at same location on hull as B175M, but on starboard side. I was hoping to get under the turbulence. Failed. Aeration at 10 knots

Simrad 3 in 1 transom skimmer - great under 10 knots. off the boat now.

B150M - the first guess. Worked OK except in choppy seas. starboard side. closer to keel, about 8" off the transom. I don't have a picture of this one, but I can take one if you are interested.

Furuno B60 - This is in the same spot as the old B150M. 50/200 no chirp. Tracks bottom better than the B150M, but not perfect. At least I can check depth at speed.

In my opinion the turbulence off the first (short) strake is a killer. I fish with a friend that runs a 32 BW outrage. 1kw fairing block transducer mounted close to keel and in the center console area. Similar deep vee hull to ours, but the strakes are carried much further aft. That unit tracks perfectly until you come off 4 to 5 footers at 25 knots.

I'd love to get a GO PRO video of the water flowing along the hull at speed from the sea floor perspective. That would give me a good idea of where to drill the next hole.....

[Yannis]

If you added a mass of epoxy (or a piece of wood with epoxy) so that the sharp rear end of the strake was progressively fading away wouldn't it reduce the aeration effect?

[ktm_2000]

Cam,

Here's what I have to work with..... kinda limited to old motorwell. I do not think I could put the transducer under the battery boxes under the helm as that area is pretty tight and not far off the bottom of the hull. My mid section is all fuel tank.

old motorwell
https://photos.app.goo.gl/WiqsjqoQdR1riWQ67

under helm towards front fishboxes
https://photos.app.goo.gl/9T15si8rBEyJsdy67

I do not have the bow thruster to deal with and if I go a little further out from the centerline I will still be inside that first strake. I could also cut some of the flange out of the grid going horizontally but do not think that would be worth it to gain 1.5" further forward.

[Carl]

Assuming your bottom is solid I can add a little light on placement.

Place transducer in a bag of water, seal top, place in the hull where you'd like to put it and take for a ride. Not liking the results, move it till you do. If ducer sits funky, try a cable tie to... or lay it next to...

I thought the ideal placement would have been at the keel just in back of main/cabin bulkhead with nothing in front to obstruct, just clean water...or so I thought. I lose bottom getting on plane. I moved forward of bulkhead on center, hardly a difference. Moved outborad both ways is better, but not a great bottom lock. Three feet forward on the keel, slightly better. Moved about 6" to port and I read bottom to WOT...27-28mph. Tried moving to Starboard side, ok, but not as good.

What I do not know is if directly over the keel the glass is thicker or maybe the water just runs cleaner to the sides. But interesting how a little change in location makes a big difference.

[Tony Meola]

I second what Carl said. Test is out.

Mine sits on the starboard side about midway between the center line and the engine bed stringer. Why did we choose that spot. We didn't, back in 1975 when my father purchased the boat, the electronics dealer, (Charles Rogers) said from their experience that was the best place so that is where it is.

It works at all speeds and the only time I have issue is if I get a boat in front of me running in the bay or if I start getting into some skinny water that has really soft mud.

I assume that the soft mud is screwing with the signal bouncing back to the transducer. But once I am back in deeper water, mud or no mud no issues.

[CamB25]

Testing without drilling holes in the boat is a good idea. I would not use the 1kw transducer for the test as it needs water flow for cooling. An in-hull transducer, like the P79, might work...https://www.thegpsstore.com/Marine-Elec ... rmin-6-Pin

Matt, I'll take a picture of my motor well for comparison. The best return I have is aft and near keel.

[CamB25]

Here are a few images of my situation

1) B60 (former B150M). 8 inches off keel, 5.5 inches forward of transom. Works purdy good. Will lose bottom in choppy conditions. Furuno MFD

https://www.amazon.com/photos/shared/9Q ... 75TkhWYX2s

2) Fairing block 50/200: about 16" off keel to starboard. As far forward in motor well as I could mount it. nothing over 10 knots. Disconnected from system.

https://www.amazon.com/photos/shared/FR ... a0EGfoArL6

3) 1k B175M: Same spot as #2, but on port side. nothing over 10 knots. Great for trolling and finding that perfect bottom spot. Simrad MFD

https://www.amazon.com/photos/shared/RU ... HOzaVb4MP2

The rounded bottom on these boats... maybe that causes water to push laterally on the hull rather than slicing like a sharper keel?

If I can find cheap in hull transducer like the P79, I'll try just forward of the bilge pump, right on top of the keel.

Cam

[ktm_2000]

I finally got some free time and got to follow Carl's suggestion of making a bag of water and then resting the transducer on top.

The seas were calm and the 1kw B175HW is on the left the 3in1 transducer on the right
https://photos.app.goo.gl/N764nrhg58Gf4aU18

I was seeing some interferance with some vertical banding when the regular ducer was running (close to 200) and the 1kw was on high chirp
https://photos.app.goo.gl/DPPFAE2oK9TdvS8H6

I was able to set the 1kw to 170 and it took care of the banding, having both the HW and sidescan running at once on 2 separate machines is quite nice. I didn't go too far from the ramp and we found some bass right near the entrance to the canal near little harbor beach. I was able to cheat with the side scan and picked up a couple slot fish.

Cherry on top, my one good location for the ducer holds bottom at 28kts. Hopefully when I cut the hole and it is exposed to water it will be a bit more clear. I also want to see how much tuning I can do.
https://photos.app.goo.gl/xtRoBriss3NsNsEs6

[CamB25]

Where on the boat is the magic spot? In my mind I'm thinking absolute dead center on the keel. The keel is so rounded that it's almost flat and it's far away from the chine wash. 600 watt should fit flush, but the 1k might not.

[Carl]

Matt, I've always put the transducer in the bag thinking water encompassing ducer would eliminate air voids. But I guess on top would have bag contour to the ducer doing the same. I think also big power ducers create heat or something needing to be in something not air. Thought I read about not using when boats not in water.


Why two different depths in first pic as bottom looks flat and ducers as kinda side by side. A foot difference in 16-18' is a difference.

I like the 1kw definition, but could live with the other. I'd love to dive under to really see what is there though.

I do like side by side comparisons. thx

[ktm_2000]

Cam,

I am diagonally infront of the thru-hull as shown in the pics of the bronze nut.

I am thinking you are dealing with your bow thruster leaving air bubbles. But even that theory gets rejected at higher speeds as even the thruster would be out of the water and not leaving a bubble trail.

Carl,
I have a chamber vacuum sealer and made a bag filled with water and during the test I had my wife sit with her feet in the hatch holding the transducer in place. I'll be honest, I did not pay attention to which way the arrow was pointing so I might not have had the 20 degree angled the right way. Even still I think the newer transducer is probably 1' lower in the boat.

As for cooling, it had rained heavily the night before and I didn't wait and drain the boat before putting in the drain plug, there was an inch or so of water in old motorwell area, that plus being on the water bag kept the transducer cool. I did check that it wasn't getting warm in any way.

dumb stuff, I would have thought HD would have a hole saw, think again.... 3 1/2", 3 5/8", and 4" no 3 3/4", neither did lowes or tractor supply, I had to order that, just came in today. I put a nice big hole in my boat, I was smart enough to get a fresh tube of 5200 but would you think after a complete gut reno last year that I would be able to find a caulking gun?? nope, will run out tomorrow for one and try again right after work as I am not going to get eaten by mosquitoes working at dusk.

hopefully I can get a better image in deeper water comparing the 2. I will have to figure out how to keep the frequecies separated, there was more cross talk than I would have expected. I might have to set the older transducer at 50, and new at 200.

[Tony Meola]

5200 for a transducer is over kill. You will regret it when you need to change it out.

[Carl]

You should have asked me Matt, I now have more caulking guns then I know what to do with. Had a time everyplace I was, had the caulking gun at the other place...so bought a new one to get job done. Then not sure I had gun at shop so took on from house, did that a couple times...then need one at house so Home Cheapo I go for another as they are all at the shop.

Yes, whatever size hole saw you need you will not have nor will Home Cheapo, Ace or...

Vacuum packed water with the Mrs holding in place. Beats my glad bag with zip tie dropped in bilge...ok I wedge it in next to the water tank so it sits properly.

Cooling...as long as you were aware, and you are.

Gotcha, angle and or location is more different between ducers than I understood accounts for variation in depth. I know you were hunting for best signal location at speed and not depth, I was just curious. Thanks.

[ktm_2000]

the results after full install??

good but not great, not the transducers fault, this one is the boat and my limited options for placement.

from the bottom - I removed the tape and am thinking there is a 1/8" ridge all around the transducer, I may try to add a fillet to see if it helps at high speeds. the photo is deceptive, the thru-hull is right near the keel.
https://photos.app.goo.gl/y2EJgNdC6A5dMXup7

at low speeds - this time I switched the transducers to final position, the 3 in 1 on the left set on medium chirp, B175HW on the right set on high chirp. You can mark individual fish off the bottom with this, was on the side of the canal near stony dike, would have been scup and black sea bass, nothing big. pretty good detail here
https://photos.app.goo.gl/urWqbxWJVhAXmdd68

as for running, at 25kts, I am marking bottom, probably not going to see fish, gets iffy at 27kts. I've been trying multiple combinations, the one that seems decent is to tuck in the outboard and try to stay bow down

also ended up with a .7 foot keel offset to match the depth being recorded.

[Carl]

25knts may not be what you were hoping for, but its not bad in my book to still have bottom lock. If looking for fish at that speed, just keep your head up cause its gonna be flying fish. No, I know fish, life you'd like to see and not pass up...

[ktm_2000]

I think I am developing a habit for a bit more speed.

I was initially concerned with fuel burn and not going too high of an RPM but I am finding that @4250 rpms I can go 27kts at only 11GPH in calm water. The boat seems like she is flying, high up out of the water, engine is not working hard. It is a bit tempermental that just a little bit more RPM and I'll be doing 4300-4400 RPM and she will be burning 13 gallons per hour. It is almost like getting to a point and opening up secondaries on a 4 barrel carb. the engine growles a bit as she starts to guzzle fuel 2.5mpg down to 2.3 mpg.

but if I can pay attention and she will stay at 2.8mpg at 27kts and that is only .2mpg less than the 3mpg I get at 25kts at 4100 rpm.

[CamB25]

As my friend says, "that's purdy good!" Better than my set up, by a 15 knot margin.

Next time you are out, heel the boat over to each side at speed and see if that improves the signal. That was my a-ha moment. When heeled to the transducer side, the signal returned. Heel the other way and it stays gone. Buried in the water = good, running in the foam/spray = not good.

Thanks for posting these data. You may have convinced me to leave well-enough alone. I can measure depth at almost all speeds and conditions with the 50/200k and, as you know, the 1kw CHIRP is great for detail at lower speeds.

Your performance and mileage is about the same as I'm getting with the 300 Evinrude. My RPMS are a bit lower- 27 knots is about 4000 rpm. In smooth conditions I get about 3mpg from 3500 - 4200 rpm. Offshore I range from 2.3 to 3. My 3mpg operating range greatly increased with the Sharrow prop. It's gets the boat up on plane quickly. The best standard (meaning not super expensive like the Sharrow) prop I found was the Merc Enertia Eco. big wide blades. great prop.

[Tony Meola]

The Thru hull might be near the keel, but is it forward or stern of the transducer? If forward, it could still be a problem throwing some turbulance.

[ktm_2000]

Tony,

the pic is deceptive, the transducer is forward and outboard of the thru-hull.