Hard to tell from pics does look close to prop radius and it looks a little low also 

 just looks low to me, try moving it up so only half of the transducer is below the hull line

Far too low as previously said

 Hmmm ok I'll try move it up then. Glad i asked as i was actually thinking of coming further down with it. Find out nxt weekend if its done the job

Cheers guys.

 The top edge is where the bottom egde should be .also make sure the trailing edge is leaning down slightly

Make sure that the trailing edge is lower than the leading edge.

 Ok well ive moved it to its new position.

The last pic of my ruler shows its height and ive moved it away from motor a bit.

I could not work out how to put that pic in this post rather than the original post. Might make it a bit confusing for some. Sorry bout that.

I'll see how it goes this weekend.

Thanks again

That looks about perfect I reckon....should work a treat

Cheers for all your help. Its been a while but im getting a lot better readings from the sounder these days. I do still get quite a bit of noise or bubbles when im cruising at 10knots or over.....but i adjust sensitivity when im underway now. Is this normal?? At what speed are most people able to still get reasonably clear readings?

 With that size of boat and a skimmer transducer, you'll never get a crystal clear picture at any sort of speed. Just the way it is. That is the preserve of well done thru-hull transducers and specialist fairings, and it's pretty common for them to have "problems" too. I run a setup like yours, and don't expect much of it at speed, so I'm not disappointed. And I was  involved with all sorts of transducer installations on larger commercial boats for a long time. I tend to think that those who claim a crystal clear picture in 200 metres at 40 knots are being a bit loose with the truth....

Looks a bit to low.

 Thanks Ranmar thats good to know. My screen becomes almost solid in colour once I'm underway.  You can still make out the bottom shape/structure though. Im guessing its from the wash coming past the transducer as im cruising. The transducer itself does throw its own litlle roostertail at speed but im guessing thats normal too?

Ill try using "high" noise rejection in between spots next time im out and see if that helps.

 Robo the last of my pics shows my latest transducer position. Do you still think its too low?

 rather than drilling into thr hull each time, why dont you get a plate mounted so you can fine tune without the worry.

Still looks a bit low in 3rd picture sackshaker, although looking at it further the cable could be a concern as well. Before you try and lift it, place cable on other side of bracket so there isn't a bend in front of tranny.
Tranny looks like it has a bit too much of a kick on it.
Hopefully you don't have any pick ups or anything protruding in the line of tranny on hull.

 Ok cheers guys

Ollie- so far ive managed to use mostly exisisting holes in the hull.......but

I do plan on getting a mount for it. Are they welded on or can i get a bolted or screw on version?

Robo- ok im gonna rerun the cable before i head out nxt and give it a try.

There is nothing protruding beneath the hull. It is completely flat ali between the keel and the chine.

Appreciate all the help fellas.

 what area are you located mate I have fitted many sounders and might be able to have a look a give some feedback. all good if you wanna figure it out yourself but if you stuck the offer is there mate

 what area are you located mate I have fitted many sounders and might be able to have a look a give some feedback. all good if you wanna figure it out yourself but if you stuck the offer is there mate

 Pm sent dreamtime

 Location angle the lot. If you where in glass boat I would lift. But it's ally. Go to high you will rock and loose signal. I run mine on first noise reduction setting. And adjust sensitivity from there. 

 Yeah cheers tommo. I rerun the cable a bit neater before going out yesty

And i think it is a bit better. Id love to know what speed people (with lowrances) still get good (or atleast half decent) readings at?

I usually adjust the sensitivity depending on what speed im searching for fish at. 

I must admit im a lot happier with it now after seeing a few arches under the boat yesterday but the cluttered screen @ 5knots or more is annoying.

 I had no probs getting a reading at 30knts on my Simrad same as lowrance with a transom mount but have gone through hull now which is better again. It takes a bit of mucking around but once you find that sweet spot it should work well. Next time your out and at speed have a look over the back see how it sits and what the water around it looks like. It should be running in clean water and the transducer sort of half in and half out. 

Also as others have said play with your sensitivity settings, on a nice day i can run mine low and if its rough need to run it a bit higher. Underway try reducing your gain until the clutter is almost gone then see what your bottom picture is like.

If "it is in a fairly "bubbly" position" then it won't matter to a large extent what settings you use (though dropping sensitivity will clear it a bit but is counter productive at some point) - as above needs to be running in clean water

Ping speed (sonar pulses per second) is what you should increase when travelling and drop when idleling along

Ok sackshaker, if you think shifting the cable as I mentioned before has made a difference it means that you changed the way water passes under transducer. I would kick that angle of transducer back now before attempting to raise the tranny up a couple notches.

 Hmm ok thanks guys. Might get a mate to grab a couple of pics of the tranny while we are under way. 

Stay posted.