The C-Brats Forum Index
HomeForumsMy TopicsCalendarEvent SignupsMemberlistOur C-DorysThe Brat MapPhotos

Both transducers losing bottom

 
Post new topic   Reply to topic    The C-Brats Forum Index -> Electronics
View previous topic :: View next topic  
Author Message
JMacLeod



Joined: 26 Jun 2018
Posts: 173
City/Region: Stuart
State or Province: FL
C-Dory Year: 2018
C-Dory Model: 255 Tomcat
Vessel Name: C-Shalom
Photos: JMacLeod
PostPosted: Tue Oct 16, 2018 9:15 am    Post subject: Both transducers losing bottom Reply with quote

We ordered an in-hull transducer as backup to be able to read depth at higher speeds than our transom mount, but both units lose bottom around 12 kts/14 mph.
Both transducers, Garmin GT51M-TM and GT15M-IH, are mounted on/in the starboard sponson, and to a sonar neophyte like myself, seem to work properly below that speed.






Since the TDs seem to function at low speed, this leads me to think this may be just a matter of positioning?
Do either of these positions look like they could be improved on/in the Tomcat hull?



Back to top
View user's profile Send private message
ssobol



Joined: 27 Oct 2012
Posts: 3362
City/Region: SW Michigan
State or Province: MI
C-Dory Year: 2008
C-Dory Model: 22 Cruiser
Vessel Name: SoBELLE
Photos: SoBelle
PostPosted: Tue Oct 16, 2018 9:29 am    Post subject: Reply with quote

My guess would be that there is ventilation/turbulence under the sponson that causes air bubbles which disrupts the sonar beam. It appears from your photos that at high speed you show zero depth which is the sonar reflection from the air in the water stream.
Back to top
View user's profile Send private message
JMacLeod



Joined: 26 Jun 2018
Posts: 173
City/Region: Stuart
State or Province: FL
C-Dory Year: 2018
C-Dory Model: 255 Tomcat
Vessel Name: C-Shalom
Photos: JMacLeod
PostPosted: Tue Oct 16, 2018 9:53 am    Post subject: Reply with quote

Yes, that was my thoughts as well.
Both transducers are mounted on the flat of the first hull step up from the bottom.
I was considering moving the TM a little lower toward the middle/bottom of the V, and the IH directly to the bottom near the bilge pump.

Where have the rest of the Tomcat owners found to be the best placement with the least amount of turbulence?
Back to top
View user's profile Send private message
gulfcoast john



Joined: 14 Dec 2012
Posts: 989
City/Region: PENSACOLA
State or Province: FL
C-Dory Year: 2010
C-Dory Model: 255 Tomcat
Vessel Name: Cat O' Mine
Photos: CAT O' MINE
PostPosted: Wed Oct 17, 2018 12:45 pm    Post subject: TC255 Reply with quote

No worries, you have a bit of positioning angle experimentation to play with.
My GT30-TM is mounted in the exact same position on that same chine and holds depth (but not CHIRP image) up to my usual cruising speed of 25MPH or so.
From about 8MPH to about 14MPH a TC255 is climbing out of displacement mode and onto plane. The angle of attack (if it were an aircraft) is changing from zero to about 5 degrees bow high, and then at max speeds back down towards 3 degrees depending on your engine trim. You don’t want to spend much time in this transition zone, as you’re throwing a massive wake and wasting gas pushing a wall of water, and many Florida boat drivers will throw their empty beer cans at you. (Some of them travel with a surprising number of those onboard, as you will soon discover).
Unlike sailors, I contend that most trailer boaters at cruising speeds don’t bother with watching the depth readout, since by the time you see an underwater obstruction on the screen at 25 MPH your prop has already passed over or hit it and you are already 10 boat lengths past it. Watch the depth and charted obstructions on your charts instead, they are on the low side (MLLW is the avg of the past 17 years lowest low water). If the height of your predicted low tide is a negative number on saltwatertides.com you’ve lost that MLLW cushion.
Smart boaters don’t go 25 MPH in 3 ft waters, and smart fisherpersons don’t fish at 25MPH regardless of depth, even with CHIRP. Use a long straightedge along the chine and beside your TM50 to level it for displacement speeds using the adjustment nuts. Enlarging your pic, looks to me like the aft portion of your ducer is too low, which will having it pinging way too forward of the ducer at planing speeds ie lose bottom. Try adjusting the aft portion upwards by 3-5 degrees using the angle adjustment nuts and I bet it will work better. These units will hold bottom in some simple boats at 70MPH (but not if the angle of attack changes to the point that the return ping is not bounced back to the unit). I believe our issues are multifactorial, and that if you must choose you’ll choose to have great performance at displacement speed (idle to 1500RPM or so, where most well designed powerboats start to plane), and some at 25MPH. At 45MPH just hope you don’t run over a small branch or the delicate piezo is toast.
Put the IH puck in a baggie of water and try it just aft of the starboard bilge pump. I have an old Garmin Intelliducer that works there at displacement speeds, not cored there per several old posts.
Have fun experimenting!
John

_________________
John and Eileen Highsmith
2010 Tom Cat 255, Cat O' Mine
Yamaha F150, LXF150
Back to top
View user's profile Send private message Send e-mail
thataway



Joined: 02 Nov 2003
Posts: 20778
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
PostPosted: Wed Oct 17, 2018 1:49 pm    Post subject: Reply with quote

For the "transom" mounted transducer a good reason why I always recommend using a Starboard mounting block. When you have to move the transducer down there may be new holes to be drilled. Are the current holes epoxy plugs with core routed out? They may be the basis for the Starboard mounts.

My Tom Cat--and other boats held bottom up to max speeds. I believe that your transducer is a little high--just from the photos.

Agree, that turbulence can be an issue as well as mounting angle.

John, I believe that the one transducer is installed "thru the hull", not shooting thru the hull. The hulls are cored--and you have to be in an un-cored area for a thru the hull shooting transducer to work.

Many power boats are not planing well at 6 mph (I hope that the comment was a bit tongue in cheek). I have seen fish caught at 12 to 15 knots when trolling in the S. Pacific.

_________________
Bob Austin
Thataway
Thataway (Ex Seaweed) 2007 25 C Dory May 2018 to Oct. 2021
Thisaway 2006 22' CDory November 2011 to May 2018
Caracal 18 140 Suzuki 2007 to present
Thataway TomCat 255 150 Suzukis June 2006 thru August 2011
C Pelican; 1992, 22 Cruiser, 2002 thru 2006
Frequent Sea; 2003 C D 25, 2007 thru 2009
KA6PKB
Home port: Pensacola FL
Back to top
View user's profile Send private message Send e-mail
drbridge



Joined: 25 Jun 2014
Posts: 218
City/Region: Sequim
State or Province: WA
C-Dory Year: 2004
C-Dory Model: 22 Cruiser
Vessel Name: Susan Marie
Photos: Susan Marie
PostPosted: Wed Oct 17, 2018 2:55 pm    Post subject: Reply with quote

While we have a 22 cruiser and not a Tomcat, We do have the same transducer. We had the same problem and the solution ended up being to position it about a 3/8" lower than the hull instead of even with it as the instructions state. It works perfect now.
_________________
Doug & Susan
Back to top
View user's profile Send private message
JMacLeod



Joined: 26 Jun 2018
Posts: 173
City/Region: Stuart
State or Province: FL
C-Dory Year: 2018
C-Dory Model: 255 Tomcat
Vessel Name: C-Shalom
Photos: JMacLeod
PostPosted: Wed Oct 17, 2018 5:07 pm    Post subject: Reply with quote

gulfcoast john wrote:
No worries, you have a bit of positioning angle experimentation to play with.
...
Have fun experimenting!
John

Thanks, John.
All good information, and I'll definitely be putting it to use.

For our purposes, the fancy TM one was meant for future fishing fun at idle speed (we're still a loooong way away from that goal at the moment), while the IH was meant just to give a current depth at speed to confirm what is listed on the charts.
I'm just starting to learn a little about the waterways around here, and I figure if I'm cruising along and start seeing depths that don't jibe with the charts, i.e. reading 5' where the chart says it should be 12' or 14', that's my cue to slow down and get my bearings/find the channel.
That sounded good in my head during the planning phase anyway.

thataway wrote:
For the "transom" mounted transducer a good reason why I always recommend using a Starboard mounting block.


Sorry, the detail on that photo wasn't enough.
We did take your advice and asked the dealer to mount the TM on a board, but there must have been some miscommunication in the process.
When I discussed it with the installer I thought we had agreed to not drilling any holes and epoxying on a small Transom-saver block to use, but when the job was done they had attached a large piece of Starboard with 6 big screws.
Not much to do about it now except hope they're epoxied and sealed well.



thataway wrote:
John, I believe that the one transducer is installed "thru the hull", not shooting thru the hull. The hulls are cored--and you have to be in an un-cored area for a thru the hull shooting transducer to work.

I've got a call in to the factory to ask about any places that are uncored on the 2018 hulls.
I will definitely update if I get an answer.

thataway wrote:
My Tom Cat--and other boats held bottom up to max speeds. I believe that your transducer is a little high--just from the photos.

drbridge wrote:
While we have a 22 cruiser and not a Tomcat, We do have the same transducer. We had the same problem and the solution ended up being to position it about a 3/8" lower than the hull instead of even with it as the instructions state. It works perfect now.

Thanks for the consensus.
I'll give it a try next time we're able to get on the water and let you know the results.
Back to top
View user's profile Send private message
thataway



Joined: 02 Nov 2003
Posts: 20778
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
PostPosted: Wed Oct 17, 2018 9:45 pm    Post subject: Reply with quote

Thanks for the clarification ref mount. I would also look at any turbulence from the Block of Starboard--I always make sure the bottom is cut flush with the bottom of the boat.

Second--what is the prop rotation--the transducer should be on the Least turbulent water from the prop--which would be on the down stroke of the blade.

Cat outboards are usually mounted opposite to standard inboards. Left hand rotation prop on the Stb side and visa versa.
Back to top
View user's profile Send private message Send e-mail
JMacLeod



Joined: 26 Jun 2018
Posts: 173
City/Region: Stuart
State or Province: FL
C-Dory Year: 2018
C-Dory Model: 255 Tomcat
Vessel Name: C-Shalom
Photos: JMacLeod
PostPosted: Wed Oct 17, 2018 11:09 pm    Post subject: Reply with quote

thataway wrote:
Thanks for the clarification ref mount. I would also look at any turbulence from the Block of Starboard--I always make sure the bottom is cut flush with the bottom of the boat.

Trimming, sanding, and rounding the board is a simple enough task.
I'll add that to my todo list.
Thanks, Bob.

thataway wrote:
Second--what is the prop rotation--the transducer should be on the Least turbulent water from the prop--which would be on the down stroke of the blade.

Cat outboards are usually mounted opposite to standard inboards. Left hand rotation prop on the Stb side and visa versa.

Looks like mine is opposite of what you say it should be.
The motors rotate outwards, meaning the TM transducer is on the inside/upward stroke side of the starboard engine.
Do you think that is as much of a factor with the added length of the Armstrong bracket separating the transducer and prop?

Back to top
View user's profile Send private message
thataway



Joined: 02 Nov 2003
Posts: 20778
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
PostPosted: Wed Oct 17, 2018 11:14 pm    Post subject: Reply with quote

It would be the normal practice to mount the transducer outward of the starboard rotation prop. Hard to say what difference the set back of a bracket/hull extension makes. One would think with that much set back it should be OK--and changing the motors or mounts would be way down the list of what you would want to do,

First be sure you can lock on bottom to at least 300 feet depth (OK, you have not gone 100 miles offshore yet!
Sad :

And be sure the bottom is held to at least your top cruising speed. The ICW and entrances change with storms and currents--so a working depth sounder is very important--only if digital display for depth.
Back to top
View user's profile Send private message Send e-mail
JMacLeod



Joined: 26 Jun 2018
Posts: 173
City/Region: Stuart
State or Province: FL
C-Dory Year: 2018
C-Dory Model: 255 Tomcat
Vessel Name: C-Shalom
Photos: JMacLeod
PostPosted: Thu Oct 18, 2018 3:09 pm    Post subject: Reply with quote

JMacLeod wrote:

I've got a call in to the factory to ask about any places that are uncored on the 2018 hulls.
I will definitely update if I get an answer.

According to the callback I got today from the mfg, the 2018 TC 255 has NO area in the hull that is uncored.
I'm a little shocked the dealer/installer didn't mention this when I asked for an IH to be placed in the uncored depression of the sponson I read about on C-Brats.

Would the transducer work as it does now through a cored hull?
It doesn't look from the photo that they cut anything out to mount the transducer inside the hull.
I imagine I could cut out a section of the inner glass and core, and fill with epoxy to avoid installing another thru-hull?
If it comes to that I'd like to be darn sure that I'm doing it in the right area first.

Now I've got another call into the dealer.
Hopefully I'll be able to speak to the installer(s) that wired the motors and/or transducer to find out how these things were installed right from the horse's mouth.
Back to top
View user's profile Send private message
thataway



Joined: 02 Nov 2003
Posts: 20778
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
PostPosted: Thu Oct 18, 2018 5:06 pm    Post subject: Reply with quote

first my bad--I did not realize that you had an inside the hull transducer. I thought it was a transducer which went thru the hull.

Second--if that area is cored, and you are getting readings Garmin has denied the laws of physics or there is a solid core. They will not shoot thru air--and the foam core is like air to the transducer.

It is possible that the installer used a hole saw and cut the inner fiberglass and core out--then installed the transducer into a puddle of epoxy resin. I think it is better to re-enforce conductive media (oil, water, epoxy, silicone etc--avoid any trapped air bubbles...)

On my older Tom Cat there was no area which did not have a core.

Looking at your photos of the sounder screens, It appears if they are all of the TM transducer. ????
Back to top
View user's profile Send private message Send e-mail
JMacLeod



Joined: 26 Jun 2018
Posts: 173
City/Region: Stuart
State or Province: FL
C-Dory Year: 2018
C-Dory Model: 255 Tomcat
Vessel Name: C-Shalom
Photos: JMacLeod
PostPosted: Fri Oct 19, 2018 8:01 am    Post subject: Reply with quote

thataway wrote:
first my bad--
...
Looking at your photos of the sounder screens, It appears if they are all of the TM transducer. ????

Shocked Shocked Shocked
Your bad?
Ha!
I think you meant MY bad.
Embarassed Rolling Eyes
I had been digging around the menus, flipping it back and forth from GT15 to GT51, and I must have experienced a dyslexic senior moment when I took those pics.
I could've sworn one of them was on 15...

...and This is why I hate getting stuck with the new guy on the job.
Razz Mr. Green

Thanks, and good eyes, Bob.
I'll revisit the IH after sorting out the TM suggestions above.
Back to top
View user's profile Send private message
JMacLeod



Joined: 26 Jun 2018
Posts: 173
City/Region: Stuart
State or Province: FL
C-Dory Year: 2018
C-Dory Model: 255 Tomcat
Vessel Name: C-Shalom
Photos: JMacLeod
PostPosted: Wed Oct 24, 2018 4:48 pm    Post subject: Reply with quote

I guess all's well that ends well, even if I'm still confused as hell.

According to the factory there's no uncored areas of the hull.
According to the installer, the IH transducer was just surface mounted as normal.
According to the chartplotter (after clearing the transducer errors, re-seating all the cables, and changing around the settings for the TDs) we are now violating the laws of physics!
Obviously someone is mistaken.

The IH is holding bottom all the way up to our WOT of 39mph.
The only time it lost bottom was when we were cruising in other boat's prop wash on the way back in from the ICW.
The transom mount (after adjusting) now holds the bottom to around 20-23mph before it starts sputtering.

So long as it keeps working, I have no desire to tear it apart.
It can keep it's mysteries for now.

This time I noticed that when trying to change the display to the GT15 from the GT51, it changed itself back and logged a disconnected error.
I must have failed to catch that the first time around.
Thanks again for pointing it out, Bob!

We'll have to wait til we learn to cross the bar before I can test it out on anything deeper than 15-20'. Very Happy
Back to top
View user's profile Send private message
thataway



Joined: 02 Nov 2003
Posts: 20778
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
PostPosted: Wed Oct 24, 2018 8:55 pm    Post subject: Reply with quote

My guess is that the area at he flat to reversed chine is either solid glass. or very resin rich..saturating what foam was there?? I have seen this in some of the boats where there is a thin band of glass/high resin concentration at the turn of the bilge or where the transom and bottom intersect.

Glad that things are working out--a few more adjustments may give you bottom up into the 30's.
Back to top
View user's profile Send private message Send e-mail
Display posts from previous:   
Post new topic   Reply to topic    The C-Brats Forum Index -> Electronics All times are GMT - 5 Hours
Page 1 of 1

 
     Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You cannot download files in this forum



Page generation time: 0.2107s (PHP: 53% - SQL: 47%) - SQL queries: 33 - GZIP disabled - Debug on