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Old 14 July 2009, 18:27   #1
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Speedo Help!

Right guys, I'm new here and first of all I just want to say I love the site! I own my own forum and I appreciate how difficult it is to get it right but this site seems perfect, good work! Now, down to business!

I've just bought my first rib (but definately not my first boat, I've been on the water all my life, with my Dad most of his life too!) and it's got a fish finder on with the transducer fitted to the transom. It's a Brig 3.6m with a Suzuki 25hp 4-stroke and I'm very happy with it!

I want to install a speedo which also uses a transducer, because I've had the water-based ones before but they always cause problems for me as I beach my boats a lot and I often forget to lift the arm up, I tend to have to replace them quite a lot! lol!

So my first question is, do transducers work for speedo's if they're fitted inside the hull? Or do they have to be actually in the water?

And now, after that question it gets down to, what transducer and speedo should I get? I want a white dialed speedo but I just can't seem to find a complete set and I'm not 100% on what I'd need to put things all together. I did find a Suzuki speedo that was quite nice, but there wasn't a price of everything or what it all includes.

I realise this is a VERY long post, but I had a lot of things to say! lol! So, as the title says, I just need help! lol!

Thanks in advance!
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Old 14 July 2009, 19:50   #2
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There are, as far as I know, 2 types of speedometers for boats.

One uses a pitot tube to pressurize air in a tube that attaches to the back of the guage. The guage converts the pressure sensed to a speed reading. You find these standard on larger outboards, and sometimes as an add-on unit.

The other type uses a paddlewheel. As the boat moves, the paddlewheel spins, and generates a signal that is converted to a speed reading.

Both of these involve something in the water: either a transom mounted pitot tube, an outboard leg, or a transom mounted paddlewheel.

A third option would be to get a GPS,which will give you speed over ground. (Which differs from in water sensors as current doesn't affect it.)

jky
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Old 15 July 2009, 06:10   #3
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If you don't want anything in the water you will either need to go with a GPS or as jyaski says, a pitot on the engine. I notice yours is a 2008, so I had a quick look at the microfiche on Brownspoint - as I thought it doesn't appear to have one. If it is fitted, there will be a small rubber hose with a cap probably lurking somewhere under the steering / tilt tube.

Other thing with the pitot ones - they are not particularly accurate, in which case you might be as easy to borrow a handheld GPS, do a few runs, and just remember what speed you get at a certain RPM.

If you are definetly wanting a big white dial, Teleflex do a wide range of styles.
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Old 15 July 2009, 08:27   #4
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Ah right, so there isn't a method to hook up to a speedo that doesn't have something that's going to cause problems when beaching the boat?

I'd love a GPS but my problem is that my dash is alraedy very tight for space with my fish finder and VHF so I don't really want a GPS on top of all that just to add to the clutter! And the price is always a factor!

I know it's a large ask but I just want a dash dial but without the problem of having to pull things up when beaching! Too much to ask? I know! lol!
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Old 15 July 2009, 08:32   #5
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You could get rid of the fishfinder and go for a combi GPS/Sounder in its place.
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Old 15 July 2009, 08:34   #6
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Quote:
Originally Posted by Downhilldai View Post
You could get rid of the fishfinder and go for a combi GPS/Sounder in its place.
Yeah I had thought about that, but those are rather expensive aren't they? I haven't managed to find a good website that has all fishfinders, GPS's etc yet but I'm still looking!
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Old 15 July 2009, 09:45   #7
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Surely if you have space for a large diameter dial you can fit a surface mount for a small handheld GPS? I've not looked into this too deeply, as my trusty old brick (Garmin12) still works, but there are some pretty tiny handhelds out there for the hiking market, some I've seen will probably set you back not far off what a marine dial will cost!

I googled the Garmin Geko - found a 201 at the dizzy heights of 44! Pulled the dimensions off their website - 1.9x3.9x0.96" (49x100x25mm) - not much bigger than a standard 3" guage...... and it will talk NMEA to your radio!


The other option (and this is where it starts to get all techy) might be to fit your own pitot to the engine. You would need to somehow run a small diameter pipe down to about the middle of your gearbox, and have a suitabe sized hole pointing forward. Two problems there are 1) geting the hydraulics balanced and 2) making sure it stays put at speed!


I'd go for the GPS!
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Old 15 July 2009, 10:34   #8
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Originally Posted by 9D280 View Post
I googled the Garmin Geko - found a 201 at the dizzy heights of 44! Pulled the dimensions off their website - 1.9x3.9x0.96" (49x100x25mm) - not much bigger than a standard 3" guage...... and it will talk NMEA to your radio!
Wow, I had no idea they were that cheap! I've bought one in the past and I have to pay 150! I'm definately looking into this now! Obviously I'd like thedil but like you say, the GPS is just as small and is more accurate!
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Old 15 July 2009, 10:48   #9
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Neither did I 'till I tripped over one in an outdoor shop for 65.......

The book of words (on the Garmin site) shows a "universal mount" which you can clip to a variety of attatchements (handlebar, suction cup etc) but I can see no reason not to screw it straight to the console.

Also as it talks NMEA, if you have a DSC radio, you get that fully functioning into the bargain as well!
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Old 15 July 2009, 11:01   #10
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They seem to have a marine mount, but I can't tell whether it's a suction cup or whether it can be drilled on.
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