I've done this before.
Make a spanner out of plywood that fits the profile of the nut you are trying to remove. It can be just a 100mm round bit of ply with the profile cut out of the centre that fits the 6 profusion on the nut. Helps if you have a jig saw.
Then make a square sided tube (internal measurements of maybe 70mm x 70mm and maybe 300mm long) that you screw to the 100mm piece of ply. Now you have a wooden tube spanner. The inside of the tube has to be bigger than the depth sounder. From memory mine is about 60mm in diameter.
It a bit of a project but more than likely will work.
Another way is to try get a block of timber (best to use hard wood) about 40mm x 40mm x about 300mm long and drill 2 holes (different sizes maybe 3/8" and 7/16") through it that line up with profusion on the nut.
Now put the 2 drill bit back in the holes (sharp end in the timber) so that that they stick out of the timber like (blunt) spikes. Leave enough length sticking out on the drill bits so you can place the timber on top pf the depth sounder and the drill bits reach down into the profusion on opposite sides of the nut. Now just turn the timber.
You could use a wider piece of timber that would allows you to drill 6 holes and thus 6 drill bits sticking out that line up with the 6 protrusions.
Never give in 
(I said to use different drills bits for each hole as most people don't have heaps of the same size drill bits and the drills need to be firm in the holes)
yep, with that kind of thing it's always better to be applying force on at least two sides...
Well last night I just attacked it with the chisel in the end. But the screw on part off. But the transducer is still unmovable. Have bashed it with a hammer trying to dislodge it. Grrrrr. This morning I'm going to try phone a friend..see if I can't find a male to help
If you don't want to save the depth sounder, you could drill a hole through the centre and then hit a wood chisel into it ( that is bigger than the hole) and then put a shifting spanner on it and try and rotate it to break the sea. The reason for the hole is to make it easier to get the chisel and also give the dislodged parts of the depth sounder to go as the chisel is driven in.
If there was no hole drilled in the centre, then the depth sounder will expand outwards and make it an even tighter fit in the hull hole.
it is better to break the seal by rotating it rather than hitting it out as this may damage the hull laminations.
Good luck
Sorry to hear about lily. I thought cats wouldn't get lost overboard. ...i was wrong.
Thanks Steve . They get playing. .racing up and down the deck at night. I guess she slipped ir misjudged. I was close enough to shore she would have made it if bull sharks didn't get her first.
[:
ive got a cat i love dearly. if she fell off id be devastated!
i dont think she'll be around once im living aboard but if she is, id be netting from bow to stern and ideally training her to get back on...she has renal failure so its just a matter of time before she goes. I really thought they just wouldnt fall off. i was wrong!
I removed the housing flange outer end using a sander carefully and then just pushed it through
After trying the drill idea with the help of the slipway guy I had an idea.... a pipe over the transducer. .a bit of man strength..and viola...out she came.
[:
D]
Thanks Southace for thinking of us girls. Present and accounted for now, I simply just don't have anything to contribute. Such is my uber-boring life 
Oh McNaughtical, I'm so sorry to hear about the loss of your white kitty. So very sad for you and her feline friends .
Select to expand quoteMcNaughtical said..
After trying the drill idea with the help of the slipway guy I had an idea.... a pipe over the transducer. .a bit of man strength..and viola...out she came.
[:
D]
Chalk up another one to girl power.
Select to expand quoteSectorsteve said...
ive got a cat i love dearly. if she fell off id be devastated!
i dont think she'll be around once im living aboard but if she is, id be netting from bow to stern and ideally training her to get back on...she has renal failure so its just a matter of time before she goes. I really thought they just wouldnt fall off. i was wrong!
Yes..the netting is something I have planned. Would stop the accidental overshoot. I haven't done what some people do which is put them in the water and teach them to swim to the boat and climb up but I hang thick ropes off the sides.
My Trm is slightly weird I think she's looking to turn cockpit lights off! Who knows! I fear she goes over and never comes back....it's hard work having a cat onboard permantly but rewarding! Welcome back girls!
My Milly looks like your girl Southace. She just went down the ladder. .(I'm on the slipway at the moment)....and brought back a dirty big rat. She is looking at me like..can I bring it up on the bed? We'll be back in the water tomorrow so their trips down to dry land will be over for a while. Eeek...crunching sounds...
Time to revisit this feel good cat story.
Select to expand quotesouthace said..
My Trm is slightly weird I think she's looking to turn cockpit lights off! Who knows! I fear she goes over and never comes back....it's hard work having a cat onboard permantly but rewarding! Welcome back girls!
All cats are weird - I used to play the flute once and my cat Trug showed her pleasure by leaping onto my head and kneading my scalp. Try playing any instrument with a cat on your head.
Select to expand quotecisco said..
Is this thread about Females or Felines??
you are treading on dangerous ground there cisco !.......
I was going to say that with Southace's initial post. 
I would have titled the thread "Where are the Ladies?" rather than just "Females?". That blunt title seems to indicate a rather off hand attitude towards the fairer sex.
If my great respect for femininity that was bred into me by my parents and my generation goes against the grain of the current political correct social mores, well stiff sh1t I say.
I open doors for ladies, pull chairs out for ladies, offer my seat to ladies and let ladies pass before me. Biggest problem these days is encountering ladies to do those things for.
Most modern toilet blocks etc...are titled male and female, it's rare these days to see ladies and gentleman. My cat Trim is a female and defiantly not a lady. That is so old school. In fact Guys and girls fits the bill in modern Australain vocabulary these days.
Modern toilet blocks etc... I guess it depends on where you are. The Sheraton will be Ladies and Gentlemen. The railway station will be symbols for male, female, disabled and gay , lesbian and trans sexuals. Oh!! I forgot the druggies dunny.
But you are right, ......it is rare these days to see Ladies and Gentlemen. Decorum has gone out the window. Even Bodgies and Widgies in the 50s had a modicum of respect between the sexes. As time goes on the sexual difference has been degraded to guys and gals, blokes and shielas and dare I say kocks and ****s.
But no, today we have no less than five definitions of sexuality.
There be heterosexuality, homosexuality, bisexuality, lesbianism and transexuality. I have not mentioned beastiality yet because it is still against the law but the day will come.
Hmmmm!! "Old School". You are using that as a label in a derogatory manner. How is that for a bit of political correctness??
My life is my own and I live in the way I choose regardless of what anybody else thinks of me and that is the one true success in living.
Being a Pauper or a Prince is just an attitude.
In the same vein, but slightly different tack, do you refer to your boat as a she?
I do, but when we got Fusion I learnt the French adamantly refer to their boats as an "it".
I found it quite strange to think of a yacht as an impersonal object, I am sure they have personalities!!
This is the Internet CISCO Kid. Gender is male or female.
It's not the Sheridan!
You corrected my spelling and punchuation on my very first posts here which I found very rude , and you have continued to do this with other new posters This is not a so called gentleman thing to do on a Internet forum.
A small majority of posters have some form of an illness called Dyslexia obviously your not one of them it is rude to discriminate or try to correct them.
If you don't like how I headline my posts just move along promptly.
Perhaps start your own on your little Lotas 9.7 that never seems to get used.
Select to expand quoteShaggybaxter said..
In the same vein, but slightly different tack, do you refer to your boat as a she?
I do, but when we got Fusion I learnt the French adamantly refer to their boats as an "it".
I found it quite strange to think of a yacht as an impersonal object, I am sure they have personalities!!
Strange the French, they put gender on a whole host of inanimate objects but they don't put gender on yacht...they do put gender of boats though... le bateau
<div> is a boat, ship or dinghy. So boats are female but yachts are genderless.
