Transducer Placement

Berean · May 17, 2015

Hello,
I am in the process of upgrading electronics. My aging NavNet Furuno is adequate as far as the plotter goes, but not great. It seems to take on a mind of its own and at times will jump between settings unprovoked. The most frustrating is the autonomous propensity to "go to curser" so when I glance up at the chart I'm looking at a Myakka FL or some such. Not helpful.

However, most important is that it is a mediocre bottom machine. The current dual frequency 250/50 ducer and sounder were probably great in the mid 1980s, but now, not so much. Time has exacted its toll. But I am not going to physically remove this unit yet, it does work in the broad sense of the word.

After researching this, and in light of the fact that most of our fishing is grouper/snapper fishing in 7-30 fathoms (90% less than 18 fathoms) I decided to go with the Garmin 7610xsv with a pair of GT 50 thru hull ducers. The latter were seleted specifically for their outstanding shallow water resolution in downvu and sidevu. If I find I am less satisfied with their performance in the deeper end of common fishing depths I can add an Airmar B175 down the road.

The question I have is if other Post owners have installed dual GT 50 (or GT 51) ducers? If so, where did you mount them. Through the hull near the forward engine room? I know that the boat will have to be blocked, these ducers don't lend themselves for a quick install in the slings because they have to be faired and its a big deal. They also need 24 hrs to cure according to a Garmin installer I spoke with. He also talked about "having to pull down the headliner" and such to route the ducer cables.

Really?

I also have an ancient Simrad color machine (CRT). This dinosour does not function, but has a ducer and cables. Why can't I fish my new ducer cable behind the Simrad ducer cable? Any one tried this?

Thanks!

Capt J · May 17, 2015

The best bottom machines I've seen have the new chirp technology. I cannot remember where the 50' Post I ran had the transducer mounted, I think it was under the steps going to the engine room. in the center bilge. Cabo and most SF almost always mounts them there at the back of the engine room, right around where the shaft logs are in the center bilge offset a little bit. Your Post might have a small keel and need to go elsewhere, in this instance I see a lot of people mount them in the bilge right in front of one of the engines. If you're going to pop a hole and put a transducer, I'd put the largest one in right from the get go, if you're complaining about your current bottom picture. Also as transducers age, they get weaker as time goes on.

If Simrad can or will fix your CRT machine, that is one of the best bottom machines ever made. CRT gives you a picture/definition of the fish that LCD can never dream of. I used to use one on a commercial boat and could tell you what TYPE of fish I was seeing on the machine just by the picture on the screen.

Berean · May 17, 2015

Capt J said: ↑

The best bottom machines I've seen have the new chirp technology. I cannot remember where the 50' Post I ran had the transducer mounted, I think it was under the steps going to the engine room. in the center bilge. Cabo and most SF almost always mounts them there at the back of the engine room, right around where the shaft logs are in the center bilge offset a little bit. Your Post might have a small keel and need to go elsewhere, in this instance I see a lot of people mount them in the bilge right in front of one of the engines. If you're going to pop a hole and put a transducer, I'd put the largest one in right from the get go, if you're complaining about your current bottom picture. Also as transducers age, they get weaker as time goes on.

If Simrad can or will fix your CRT machine, that is one of the best bottom machines ever made. CRT gives you a picture/definition of the fish that LCD can never dream of. I used to use one on a commercial boat and could tell you what TYPE of fish I was seeing on the machine just by the picture on the screen.
Click to expand...

Great ideas, thanks!

The pair of GT 50's are identical in size and shape but funtion differently to proved a full picture. The stbd mounted on has a downvu and sidevu (stbd of course). the port side ducer should be at the same spot relative to the keel but on the opposite side of the keel, the ducers should be abaft one another. This ducer renders the sidevu for that side of the boat. Garmin specifies for the pair when the deadrise is over 5 degrees. This is the case with the Post, albeit, barely. Were there any thoughts of trying to get by with one, a look at the keel would put the unequivacol kabash on that idea.

Thanks for the Simrad intel, I will explore further!

Berean · May 17, 2015

'the ducers should be abaft one another'

Athwartships,not abaft

P46-Curaçao · May 17, 2015

Learned a new word (Athwartships)...and found the answer myself...yeahhhh

Berean · May 18, 2015

Now that's a cool diagram....

mwwhit1 · May 18, 2015

I can't comment on your specific units going in. Years ago I installed a combo speed, temp, depth transducer. I used an existing hole that was next to the shaft log behind the engine. Cable goes up the salon aft corner chase, you will have to remove the rear wood ceiling panel where your side window blind is, then across the center ceiling (remove that panel) and into the helm station. Don't have to touch the headliner at all. POST actually planned for someone to access this stuff!! It is a long way to the electronics box on the bridge. Can't remember exactly, but probably 25' or more from that spot.

I think the only place I had to use the old cable to fish the new one through was the aluminum pipe on the bridge going to electronics box. Everywhere else you can get to easily. Run a few extra pieces of mono through that pipe for any future wires to be pulled?

Good luck with your project.

Bill106 · May 18, 2015

You do have the GT50M-THP correct? The detail they show of bottom structure is amazing compared to conventional sonar but I think you'll find their fish detection somewhat lacking and will want to add that B175 pretty soon. The GT50's mid band 300watt CHIRP element at your depths will be close to "running out of gas" and the 1KW B175 will be much better. As far as pulling the wires goes, sure you can use the old ducer's cable as a pull string, and tagging on a couple extra pieces of mono for future use always a good idea.

Cutting the fairing blocks to match your deadrise and installing them is pretty simple, between cure times for a fast cure sealant and also priming and painting the fairing blocks with antifouling will (should) take two days. A coat of non-keytone based transducer paint on the element should also be applied. MDR is one manufacturer of ducer paint but a lot of folks are switching to the newer eco-friendly antifoulings like Pacifica or Hydrocoat. Both work fine as well and won't hurt the element.

Berean · May 18, 2015

mwwhit1 said: ↑

I can't comment on your specific units going in. Years ago I installed a combo speed, temp, depth transducer. I used an existing hole that was next to the shaft log behind the engine. Cable goes up the salon aft corner chase, you will have to remove the rear wood ceiling panel where your side window blind is, then across the center ceiling (remove that panel) and into the helm station. Don't have to touch the headliner at all. POST actually planned for someone to access this stuff!! It is a long way to the electronics box on the bridge. Can't remember exactly, but probably 25' or more from that spot.

I think the only place I had to use the old cable to fish the new one through was the aluminum pipe on the bridge going to electronics box. Everywhere else you can get to easily. Run a few extra pieces of mono through that pipe for any future wires to be pulled?

Good luck with your project.
Click to expand...

Regarding the cable, that's great info! Thanks! I will check it out next time I'm on the boat. I don't want my ducers near the running gear, even just if the shaft logs. I think I can get cleaner water a little more forward.

Berean · May 18, 2015

Bill106 said: ↑

You do have the GT50M-THP correct? The detail they show of bottom structure is amazing compared to conventional sonar but I think you'll find their fish detection somewhat lacking and will want to add that B175 pretty soon. The GT50's mid band 300watt CHIRP element at your depths will be close to "running out of gas" and the 1KW B175 will be much better. As far as pulling the wires goes, sure you can use the old ducer's cable as a pull string, and tagging on a couple extra pieces of mono for future use always a good idea.

Cutting the fairing blocks to match your deadrise and installing them is pretty simple, between cure times for a fast cure sealant and also priming and painting the fairing blocks with antifouling will (should) take two days. A coat of non-keytone based transducer paint on the element should also be applied. MDR is one manufacturer of ducer paint but a lot of folks are switching to the newer eco-friendly antifoulings like Pacifica or Hydrocoat. Both work fine as well and won't hurt the element.
Click to expand...

Yeah, I really wrang my hands about GT 50 THT vs GT 51. The former reportedly good to 100', the 51s have 600 watts and deeper penetration. However, apparently you sacrifice the clarity in shallower depths with the 51s. Since we really do fish 75' or less most of the time, I thought the GT 50's were the best option. However, not an easy decision especially because I am knowingly selecting 300 watt ducers. The 51s are only slighty more expensive, certainly not a factor in this matter. I guess I really prioritized the shallow water fishing in my decision, and stuck with it despite all the advantage of the 51s.

The B175s are far superior to determining bottom density and that is actually very important to me. I am not sure I can convince the Admiral that we need another ducer before I go to the hill to put the 50s in. Especially given I need new AC. I suspect I know what her choice would be...

Hmmmm, AC or B175s ? Let me guess..,

Even still, the B175s are on my radar...

With all that said, I can't say I feel settled abot my ducers. I might find I blew it and shoulda got the 51s. I guess time will tell absent any amplifying information convincing me to change ducers...

Capt J · May 18, 2015

Have you talked to Garmin and Airmar with your fishing needs and gotten their recomendations?

Berean · May 18, 2015

Yes, Garmin rep agrees with my choice to go with the 50s based on my criteria. He also agreed with me that the addition of the B175 is a good option to augment bottom density discernment and effective depth range.

Bill106 · May 19, 2015

75' depth makes the 50's the best choice, I wouldn't agonize over that decision and if you expand your range the 175 will handle it if or when that happens. Keeping the admiral comfortable if FAR more important!

Berean · May 19, 2015

Yessir!

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