30’ to 36’ boat owners with transom mounted transducers, I need your help

[jip40]

I have a 2002 330 express with an Airmar B164 thruhull transducer, tied into a network with a 5212 and a 5012.

I just purchased dual 1243XSV displays to replace the 5212/5012 units. The package I purchased comes with a GT56 UHD transom mount transducer. I have no experience with a transom mounted transducer on this size boat.

I’m hoping to find some forum members that can provide guidance on what I should do from a transducer standpoint. Garmin tech support told me that the B164 is compatible with the new displays, but it is an older transducer and doesn’t have the features of current models. Additionally, the B164 displays incorrect temperature readings.

One of the main questions I have is, will a transom mount transducer provide good results on this size boat with twin engines or do I need to try to sell this unit and go with a thru hull model.

Thanks in advance

Jeff

 

[Harrysea]

I have the exact same setup on my Marlin. I still have the Airmar hooked in as a backup, but have the GT56 mounted on the transom. The GT56 is phenomenal and the 1243xsv displays give great down and sidescan visibility. The GT56 holds bottom at 45MPH (a little grainy at that speed, but quite readable). I’ve been running this setup for almost two years with no problems.

 

[Sardinia306Canyon]

One of the main questions I have is, will a transom mount transducer provide good results on this size boat with twin engines or do I need to try to sell this unit and go with a thru hull model.

Yes, it will give good results on most hulls except stepped hulls but thats not the case of a GW, if installed correctly.
You may use a transom saver to be able to move the transducer to a better reading position without drilling the transom again.
Transducer location and deoth is extremely important to make him reading at speed, find a position as deep as possible and wit absolutely any thing in front of it, thru-hulls, strakes, etc.

I will install a GT51M transducer this winter and deciding if it will be the thru-hull or again a transom mount model.
In case of the transom mount model of the GT51M i will install it center keel between the engines where the drain plug is as i don't need the drain plug and will pull it and glass the hole shut.

I had the GT51M-TM on my Venture 34 on the stepped transom she had and transducer was reading at 35 knots.

Chris

 

[Stickbo]

I as well have that same transducer set up on my 330. Only difference is I have Garmin 7612 MFDs. Both transducers are plugged into the screens so I can jump back and forth between the two. The GT56 is mounted between the engines (let me know if you want a pic) and holds bottom 95% of the time. Sometimes if its rough it gets wonky if were steaming.

 

[jip40]

I have the exact same setup on my Marlin. I still have the Airmar hooked in as a backup, but have the GT56 mounted on the transom. The GT56 is phenomenal and the 1243xsv displays give great down and sidescan visibility. The GT56 holds bottom at 45MPH (a little grainy at that speed, but quite readable). I’ve been running this setup for almost two years with no problems.

Thanks for your response. Where do you have the GT56 positioned relative to the engines & do you get any prop wash interference?

 

[jip40]

I as well have that same transducer set up on my 330. Only difference is I have Garmin 7612 MFDs. Both transducers are plugged into the screens so I can jump back and forth between the two. The GT56 is mounted between the engines (let me know if you want a pic) and holds bottom 95% of the time. Sometimes if its rough it gets wonky if were steaming.

Thanks, where do you have the transducer mounted & do you notice any prop wash interference

 

[wspitler]

I have the same set up on my 2007 330. The GT 56 is centered between the engines and is driven by a 1243xsv. I also have the original through hull transducer that works as well.

 

[jip40]

In case of the transom mount
I had the GT51M-TM on my Venture 34 on the stepped transom she had and transducer was reading at 35 knots.

Chris

Chris, is it possible or even feasible to mount that transducer flush on the bottom of the boat instead of on the transom

 

[jip40]

I have the same set up on my 2007 330. The GT 56 is centered between the engines and is driven by a 1243xsv. I also have the original through hull transducer that works as well.

From the photo it appears that the transducer covers the bilge drain which I can’t do as I plan to move from a wet slip to dry storage in the spring

 

[SkunkBoat]

Use a SternPad(JUMBO) find on amazon. Right next to drain plug. Works really well.


I eventually mounted a thruhull GT51 on the centerline in place of the old B744.
Works way better at speed.

 

[Sardinia306Canyon]

Chris, is it possible or even feasible to mount that transducer flush on the bottom of the boat instead of on the transom

There is some people here in Italy who mount transom mount transducers on a home made SS bracket at the keel just on the transom for the reason that they can pull the transducer easily when loading the boat on a trailer. In this case the transducer is mounted backwards (stern part goes forward) to have the cable coming up just on the lower transom edge. this works on Lowrance units as the transducers direction can be inverted on the Lowrance unit, but not sure if that would work on Garmin units. If you are interested in that i have to search for some videos in italian language who show how it's done, but on Lowrance units.
Most of them use that system on smaller RIb's with single outboard what means that the transducer is in front of lower unit and propeller, what is generally not recommended as it ma create turbulence to the prop making it work inefficient. Those transducers are the flat, long 3 in one transducers like the GT51M and probably don't work with a higher building transducer.
In your case with twin outboards this will not be a problem as transducer will sit in between the engines, but i would either recommend to use the normal stern mount on a transom saver or change the transducer to a GT51M-TH or the twin GT51M-TMP transducer and install it thru-hull version TM51M-TH.
Both options ore shown very well on Skunkboats photos above, but will not work if you trailer your 330 Express.

I don't see a a real need to have a drain plug and know also that the often leak leading to wet transoms.
If i had none i used the bilge pump to empty most of the water and mop up the remaining little poodle, not a problem for mainly slipped boats and a little annoyance for frequently trailered boats.

Chris

The B164 is a decent transducer, i had one on my RIB together with a TM265LH what was not reading over 8 knots.
As i need the TM265LH only for really deep deep dropping it was not a problem for me, so in case you will have problems with noise at faster speeds then you may do the same, use side-scan at lower speed when it works best and the B164 a faster speeds. Thats what i did successfully for the last 4 years.

Chris

 

[wspitler]

From the photo it appears that the transducer covers the bilge drain which I can’t do as I plan to move from a wet slip to dry storage in the spring

My garboard plug is still reachable as the mounting plate is slightly above it with the transducer cantilever down over it. I can still unscrew it. The mounting plate is centered directly over the garboard plug.

 

[DennisG01]

Just a side note... size of the boat has nothing to do with this, at all. All the transducer cares about is smooth water flow. This is easy enough to figure out just by looking at the hull vs the engines, tabs, strakes and any other thru-hulls you already have. As long as you are about a foot away from the props you're good - you can be closer to the other things.

If you can, just look at the water flowing off the hull when on plane. But it's still very straight forward/easy to figure it out if you're on the hard.

Once you look at your hull, between that and reading the directions, it takes about 5 minutes to figure out where to put it. It's an easy peasy thing

 

[Sardinia306Canyon]

Oh, yes, i have overseen that Skunkboat's transducer is on the side of the garboard plug not in front of it.
However, it does matter, or not, all depends how frequently the garboard plug is used.
Chris

 

[Sardinia306Canyon]

It is also to mention that the GT56UHD transducer is not necessary the best option depending on the kind of fishing used for.

The GT56UHD transducer is a

• high frequency UHD transducer, very good for best sideVü and DownVü, but limited in depth
• wide cone transducer with a 24-16° beam with in traditional sonar. what is good for finding mid water fish but not so good for pinpointing fish living on the bottom
• has lower power

I believe that the GT51M is the much better transducer for showing traditional sonar display and still good for SideVü and DownVü with lesser details but going deeper due the higher power.
Thats why i choose the GT51M over the GT56UHD

GT51M
Frequency: CHIRP Mid-band (80-160 kHz); ClearVü/SideVü CHIRP 260 kHz (245-275 kHz) & 455 kHz (445-465 kHz)
Beam Width: Traditional: 24°-13°, ClearVü/SideVü: 2.0°x51° @ 260 kHz and 1.4°x29° @ 455 kHz
Power: CHIRP Traditional 600 W; ClearVü/SideVü 500 W
Depth: Traditional: 1,800 ft.; ClearVü: 1,000 ft.; SideVü: 750 ft.

GT56UHD
Frequency: Traditional High-wide CHIRP (150-240 kHz); ClearVü/SideVü 455 kHz (425-485 kHz), 800 kHz (790-850 kHz), 1000 kHz (940-1100)
Beam width: Traditional CHIRP: 24-16; ClearVü 0.52 x 52 @ 1000 kHz, 0.64 x 35 @ 800 kHz, 1.1 x 52 @ 455 kHz; SideVü 0.52 x 52 @ 1000 kHz, 0.64 x 35 @ 800 kHz, 1.1 x 52 @ 455 kHz
Power: Traditional 350 W; ClearVü/SideVü 500 W
Depth: Traditional: 800 ft freshwater; ClearVü: 400 ft; SideVü: 500 ft

For fishing in more shallow water the GT56UHD is the better choice while the GT51M is the better choice for deeper water but with less SideVü and downVü capabilities and resolution.

Chris

 

[Harrysea]

Thanks for your response. Where do you have the GT56 positioned relative to the engines & do you get any prop wash interference?

The transducer is mounted about 6” starboard of the keel. If you enlarge the picture, you can see it down low, just a touch off centerline. No prop interference at all.

 

[SkunkBoat]

There is some people here in Italy who mount transom mount transducers on a home made SS bracket at the keel just on the transom for the reason that they can pull the transducer easily when loading the boat on a trailer. In this case the transducer is mounted backwards (stern part goes forward) to have the cable coming up just on the lower transom edge. this works on Lowrance units as the transducers direction can be inverted on the Lowrance unit, but not sure if that would work on Garmin units. If you are interested in that i have to search for some videos in italian language who show how it's done, but on Lowrance units.
Most of them use that system on smaller RIb's with single outboard what means that the transducer is in front of lower unit and propeller, what is generally not recommended as it ma create turbulence to the prop making it work inefficient. Those transducers are the flat, long 3 in one transducers like the GT51M and probably don't work with a higher building transducer.
In your case with twin outboards this will not be a problem as transducer will sit in between the engines, but i would either recommend to use the normal stern mount on a transom saver or change the transducer to a GT51M-TH or the twin GT51M-TMP transducer and install it thru-hull version TM51M-TH.
Both options ore shown very well on Skunkboats photos above, but will not work if you trailer your 330 Express.

Neither are a problem when the boat is hauled on a trailer

 

[DennisG01]

Neither are a problem when the boat is hauled on a trailer

I wonder if Chris has different trailer setups than we generally do here in the States.

Chris, we generally setup our trailers so that no rollers/bunks extend past the transom - and there is a "bow stop" so the boat physically can't go any further. There are some cases where our bunks extend aft further... but in those cases, the transducer is mounted far enough away to avoid contact.

 

[Sardinia306Canyon]

Yep, good find, i forgot that Americans float on trailers with bunks and i trailered my boats in Costa Rica wth a US style trailer, but forgot about that.

We have a bit different trailers, in steel and not aluminum and we don't use bunks nor can we trailer over 8.2ft wide for locals law in Europe. Also Italians don't put more then the lower tire in the water, to not ruin the drum brakes and axle hub, so almost no float-on trailers. Italians wrench the boats up with the winch and keel rolls on the central roller on the most rear beam, and the Transom sit there, not behind and suspended.
European trailers have dual/triple rollers on the side and center rollers for the keel so a thru-hull would most likely hit a roller so all boats frequently trailered have transom mounted transducers or the transom mount transducer in the sled bracket i tried to explain before.

Trailer weight for normal cars and drivers is limited to 3.5 tons / 7700 lbs or max weight of car/truck and loaded trailer can not exceed 13'200 lbs. More is possible for trailers with air brakes but need a special driver licence.

The one below is a small trailer for a probably14ft rib, bigger ones have more rollers and some twin axles but for max length boats is usually not more as 28/30ft as boat width would exceed the 8.2 ft permitted.



This one is a 7700 lbs trailer



Chris

 

[SkunkBoat]

I have a 2002 330 express with an Airmar B164 thruhull transducer, tied into a network with a 5212 and a 5012.

I just purchased dual 1243XSV displays to replace the 5212/5012 units. The package I purchased comes with a GT56 UHD transom mount transducer. I have no experience with a transom mounted transducer on this size boat.

I’m hoping to find some forum members that can provide guidance on what I should do from a transducer standpoint. Garmin tech support told me that the B164 is compatible with the new displays, but it is an older transducer and doesn’t have the features of current models. Additionally, the B164 displays incorrect temperature readings.

One of the main questions I have is, will a transom mount transducer provide good results on this size boat with twin engines or do I need to try to sell this unit and go with a thru hull model.

Thanks in advance

Jeff

If you have two 1243xsv then you can run the GT56 from one and the B164 from the other(you need a Bare Wire to 12 pin adapter Garmin adapter).
Also then, you can share sonar between either of them using Garmin Network. Although side by side that would not be very useful.

The B164 is old school 50khz/200khz CW sonar.The B164 is 1000W. The thru hull B164 will read bottom at speed way better than the GT56 TM.
Check the B164 wiring for the Temp(white wire)

The GT56 is CHIRP and sidevu.The GT56 is only a 300W traditional(the GT51 is 600W) It has a 12 pin connector already.The GT56 will give you Temperature

My opinion, you can get away with using the GT56 TM for bottom fishing since you have a B164.

You just have to get the GT56 just right so it is not throwing water and messing with flow to props.
It will read sidevu great at trolling speed/"looking for wreck" speed. You will need to use "Traditional mode" at speed.
I often have a split screen Traditional/Sidevu when wreck fishing.
The Thru Hull version GT51M on the centerline is fantastic. Even sidevu at 20mph you can do circles and find wrecks.
You can literally see a picture of the wreck even way off to the side vs. a red blob only when you are right on top of it using Traditional.

When it comes to transducers, you have to read the specs. The expensive one's are more expensive for a reason. They have bigger ceramics or more of them or both.

Here are some links to posts about Garmin sonar and transducers

https://www.greatgrady.com/threads/garmin-researching-my-upgrade-options.31321/

https://www.greatgrady.com/threads/265-mods.25902/post-212965

https://www.greatgrady.com/threads/shoot-thru-tub-in-265express.31336/

https://www.greatgrady.com/threads/sidescan-xducer-mounting.25392/