Marlin transducer flats

[SkunkBoat]

Skunk, I think they are flush mounting transducers on a hull with a 20 degree dead rise, therefore they need a 'ducer with a 20 degree tilted element, in order to shoot straight down.

but if its a moulded in flat spot on the hull then they need a 0 degree. Am I missing something?

like this picture I found from another thread here

 

[glacierbaze]

I don't use through hulls transducers, so I am not sure if "flat" is being used interchangably with "horizontal" to the waterline. I had 'ass'umed that flat just meant flush mounted to the hull, without fairing blocks to compensate for the angle.

 

[mleads310]

It is flat/horizontal to water line. In fact, when you go to install the ducer, you will have to make a sort of angled washer to compensate for the inside angle of the hull.

 

[SkunkBoat]

It is flat/horizontal to water line. In fact, when you go to install the ducer, you will have to make a sort of angled washer to compensate for the inside angle of the hull.

hehehe I'm sorry if I don't get it. Your second sentence seems to contradict the first.

I'm just trying to clarify things, maybe I'm muddying them up.
This thread seems to talk about mixed things...the size of the flat, B744 thru hulls and B175 flush mount thru hull transducers.

I don't have "transducer flats" on my 265 but I know what they are. They are flat (parallel to water line) inside and out so that you can easily mount a thru hull transducer(like a B744 or B765 or possibly a larger B275 ) without using an angled fairing and without drilling angled holes.
A B765 is a dual channel CHIRP 600W that with fit the hole left by a B744. It has the same 2" dia post and 5.55" size. The B275 is a 1kw dual channel chirp that has a 1" post and its 8.5" long (without fairing). That would seem to fit the Transducer Flat.

The "flush" style B175 single channel CHIRP comes in a 20 degree tilted element if you are mounting thru the angled part of the hull.
If you are mounting it on a "Transducer Flat," you would use a 0 degree B175. Right?
TortugaBob seemed to say that he has B175 20 degrees mounted on the flat. That is what I was questioning. It doesn't sound right.

 

[mleads310]

No worry at all. Maybe I didn't describe it as best as I should have and to be honest it's pretty hard to write and much easier to describe when looking at it in person.

Regarding the transducer flat:
The flat itself (looking from the outside/ bottom of hull) is parallel to the waterline. But from the inside, even tho it looks flat it's slightly angled. Maybe a quarter inch aft to bow.....at least this was the case with my boat.

Even tho the transducer flat is flat from the outside......and even tho it "looks flat on the inside bilge area" it isn't completely flat on the inside of the bilge area. The flat portion inside (bilge area) still has a slight angle Therefore an angled spacer was needed to be used for the inside to compensate for the angle.

My boat had an angled spacer with the original b744 and my marina had to make another one when it was replaced with the b765hl. To be clear it wasn't drastic but it was absolutely noticable. They even tried to install the replacement transducer without the angled spacer and you can see a slight gap on one side of the threads facing towards the bow.

Regarding the b765hl:
yes it's a direct replacement for the b744, and it upgrades you to chirp and also compatible with newer units. This does fit (dimension wise) on that transducer flat. Same dimensions as a b744. I couldn't find a better option that would fit on that transducer flat. I was hoping I could find something that would be 1k, have similar dimensions and compatible with my axiom pro, but at the time I couldn't. If I recall even tho the outside/bottom hull side of the flat was approx 8 inches.... A transducer larger than the b765hl wouldn't sit flush with the bottom of that transducer flat as It's slightly tapered towards the bow end of the flat and caused an issue.

Regarding 0 degree, yes definitely use a 0 degree on that transducer flat.