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Author Topic:   Through hull transducer - wow what a difference
russellbailey posted 07-01-2014 05:26 PM ET (US)   Profile for russellbailey   Send Email to russellbailey  
I just got back from two weeks of boating near Morehead City, North Carolina, in our 1984 Outrage 25 with twin 2006 Optimax 150s. It is a great place to boat.

In prior years, with a transom mounted transducer, whenever I got into shallow water there would be interference with one of the motors and the unit would stop reading (less than 5'). If you know the backwaters in that area, 5' is not shallow at all, so for where I really needed the depth finder it was useless. I'd had lesser problems before with the transducer on our Striper 15 with single engine, where it would read down to about 3' before pegging and not giving a number.

Last year, I installed a through-hull transducer in the boat. I picked the Airmar SS264. Since most usage for me is fairly shallow, I went with the 200 kHz model in the wide configuration. I considered a more typical B64, but I was hoping that the taller height of the SS264 would simplify installation (it did somewhat). I drilled a large hole in the fish well on the port side, then a larger hole on the inside to seal off the core with resin and fiberglass, and then a larger hole yet to "countersink" the transducer nut slightly since the hull was too thick for the thread depth on the transducer. If you've done any fiberglass work before it is not complicated to do but drilling the big hole does take some nerve (I've got a neat hull core piece I saved from the install). The transducer is mated to an NSS8 transducer.

The transducer reads accurately down to 1' under the keel, at which point I can feel the motor bumping bottom with the skeg. It holds clear readings perfectly through turbulent water and waves and such, and it is difficult to ever get it to lose a reading (the only time I succeeded in doing so was when I was in a lot of aerated whitewater behind a large powered catamaran, and then only briefly). It also gives very clear readings in more normal depths.

I've searched and read some on ContinuousWave about a few others who installed through-hull transducers. After seeing the difference of using one, I have a strong preference towards them for my uses, and the install is manageable.

[Note - the Outrage 25 has a place in the forward storage locker where the hull is basically solid, but that is so far forward I did not use it - I wanted the transducer near the stern so it keeps good contact - it is about 3-4' in front of the stern]

dfmcintyre posted 07-01-2014 09:05 PM ET (US)     Profile for dfmcintyre  Send Email to dfmcintyre     
Russ -

Interesting. We mounted a through hull up forward in our '25 Revenge. Had to build a fairing block so it would point straight down. At certain speeds, and trim, it would make a weird moaning noise. The factory sent me a diagram for placement.

Regards - Don

bluewaterpirate posted 07-02-2014 09:48 AM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
Russell ...

Great info. Sorry I didn't call you I lost my mom Saturday night she was 99 years young and still vibrant to the end. Glad you had a great time!


swist posted 07-02-2014 11:04 AM ET (US)     Profile for swist  Send Email to swist     
It's no secret that through-hull transducers give much better readings. And no ugly contraption and wiring sticking out from the transom.

I installed one on 24' ProLine a long time ago, and got similar results to you.

My biggest issue is that while my current transducer will see the bottom at 3' or even 2', it takes almost nothing to have it fly off with some silly reading like 675 feet - wakes, tidal currents, rough water, growth on the sea floor.

I am really leery about drilling holes in a Whaler, so I have not considered switching.

russellbailey posted 07-02-2014 11:23 AM ET (US)     Profile for russellbailey  Send Email to russellbailey     
Tom, sorry for your loss but it sounds like she had a great life. We did about 200 miles of boating while there - one flat day out at Shark Island was really neat. I did find 3-5 at 5 sec got me seasick one day - I'd say that is my limit. Lots of Spanish mackerel on planers were caught.

Don, this through hull is a tilted element transducer - it barely protrudes from the bottom of the hull and mounts flat against it - no noise at all. You purchase the right tilt for the hull deadrise - very slick setup.

swist, I have not seen any bogus readings except for that highly aerated water I mentioned (it was really foamy behind a large boat). It is really impressive how it holds on. I was previously cautious about drilling a hole in the boat but now that I've done it and seen how easy it was I'd not hesitate to do it again - the hardest part is managing the heat of the curing resin and even that was workable.

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