speedometer

Designs for inboard or outboard power

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jamundsen
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speedometer

Post by jamundsen » Thu Aug 12, 2010 5:01 am

My speedometer has a water pickup and pitot tube for reading the speed. Are there other ways to make this work without the tube mounted on the back of the boat?
John Amundsen
Monte Carlo
Lakeland,Fl

Work tends to get in the way of boat building

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DaveLott
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Re: speedometer

Post by DaveLott » Thu Aug 12, 2010 5:04 am

John- Mine has an adapter to mount underneath.

I ran my tube out the transom as low as I could get it leaving very little of the tubing visible.
Dave

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Oyster
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Re: speedometer

Post by Oyster » Thu Aug 12, 2010 5:20 am

jamundsen wrote:My speedometer has a water pickup and pitot tube for reading the speed. Are there other ways to make this work without the tube mounted on the back of the boat?
There are several thru hull mounted transducers used by Navman and Raymarine. If I recall correctly, Raymarine unit is the ST 40. Years ago Datamarine made just a unit exclusively that even had a removable transducer so that you could clear the wheel of seaweed and or any growth that built up in the wheel from boats such as big yachts and sailboats that sit in the water.

Actually check out this link for a quick reference and what they look like for thru hull installation.
Then there’s DMI Marine which not only has parts for many Datamarine instruments but also makes new “Phoenix” speed and depth instruments (seen at top) that fit Datamarine hull and bulkhead holes. They use NMEA 0183 Smart sensors, which seems wise, and there’s a Phoenix wind instrument coming. Anyone had experience with any of these companies, or any sort of instrument upgrade?
http://www.panbo.com/archives/2007/12/o ... ubled.html

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BruceDow
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Re: speedometer

Post by BruceDow » Thu Aug 12, 2010 6:11 am

I know that this is slightly off-topic, and would not work with you current speedo, but if you had money to spare, you could go the Mr. Hot Rod way...

Built-in GPS Speedo....

http://www.livorsi.com/catalog/gps.htm
Bruce.

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~~ To me - only my boat is not yet perfect. Everybody else's is to be admired for I know the path they have walked (Dave Lott, 2010) ~~
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Trackhappy
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Re: speedometer

Post by Trackhappy » Thu Aug 12, 2010 3:50 pm

Cassell Marine over here in AUS have a through hull pitot fitting. I am sure there would be similar available in your area. If they won't post OS, and you need it from here let me know and I will purchase and post for you.

http://www.cassellmarine.com.au/p/11126 ... -hull.html

Cheers,
Glenn.

Edit: Just looking at it, anyone with a lathe and a bit of bronze bar should be able to whip one up for you in no time. I would guess as long as the horizontal hole is the same size as the hole in your original then not much else would matter.
By the time I have built a boat, I'll be ready to build a boat....

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jamundsen
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Re: speedometer

Post by jamundsen » Thu Aug 12, 2010 4:02 pm

Thanks Glenn. Thats another good idea.
John Amundsen
Monte Carlo
Lakeland,Fl

Work tends to get in the way of boat building

John K
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Re: speedometer

Post by John K » Fri Aug 13, 2010 4:33 am

Transducers do not work thru the hull on wooden boats. You would have to cut the wood hull and fiberglass in a patch to mount the transducer. My hull was already completed and painted when I realized how I had to mount it, so it went over the transom.

Pitot tubes are not the most reliable way to measure speed. they can be off by 5 to 10 MPH.

jcallends
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Re: speedometer

Post by jcallends » Fri Aug 13, 2010 5:07 am

I'looking for something similar and have had the following thoughts, some fish finders have a small spinner that attaches to the hull and is quite accurate and gives your speed reading in a corner of it's screen, also what about useing a GPS unit? Wouldn't it show MPH on water as well as land?

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Caber-Feidh
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Re: speedometer

Post by Caber-Feidh » Fri Aug 13, 2010 1:12 pm

Forget the pressure reading gauges, and spring for a GPS based gauge




Funny, my boats were always faster before I installed GPS speedos :wink: :? :? :shock:
Some plan to stroll through Saint Peter's Gates, I plan to go through them at 150mph... backwards... in a screaming ball of flame, with a glimmer belt wrapped around my head, and a NOx button in my hand.

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Roberta
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Re: speedometer

Post by Roberta » Fri Aug 13, 2010 1:57 pm

I have a Garmin Colorado with the Inland Lakes data base in it. We used it when we rented a houseboat on Lake Powell. What's nice is you get the GPS speed and it also shows shore lines and water depths (based on certain levels). I think I will use it to establish my speed to see what my zip will do, then not bother. I will install a tach to make sure I am pitched correctly and to monitor engine performance. I can always take the GPS whenever I feel I need to know the speed of the boat. Being I will be running an old 2 stroke OB, I will limit my gaging to Volts and RPM. I subscribe to the KISS analogy.

Roberta
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

John K
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Re: speedometer

Post by John K » Sun Aug 15, 2010 5:03 am

jcallends wrote:I'looking for something similar and have had the following thoughts, some fish finders have a small spinner that attaches to the hull and is quite accurate and gives your speed reading in a corner of it's screen, also what about useing a GPS unit? Wouldn't it show MPH on water as well as land?
The paddle wheel type is what I installed on the boat. It is fairly accurate to a GPS. Not all GPS do speed, just have to read specs to make sure what you are buying.

upspirate

Re: speedometer

Post by upspirate » Sun Aug 15, 2010 5:12 am

One thing to consider....what you want the speedo for.

A GPS based unit measures speed over ground,a pitot or waterwheel speedo measures speed though the water.

If using for navigation, the speed over ground type is what you want,the others will throw off your actual speed depending on current

The GPS unit is accurate too,while the others aren't

bigfoot
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Re: speedometer

Post by bigfoot » Sun Aug 15, 2010 2:56 pm

Whether you use a speedo with a pitot tube or the depth finder with a paddle wheel, I suggest you check the accuracy with a handheld gps. My brand new dash mounted guage always read lower than the depth finder. I assumed it was the inaccurate one and sent it back for calibration. It came back reading the same way. I finally carried a portable gps along and discovered that the paddle wheel depth finder reading was very optimistic about my speed. The dash mounted guage was the correct one. To my thinking, either one, once mounted is pretty unnoticeable.

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thudpucker
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Re: speedometer

Post by thudpucker » Sun Aug 15, 2010 10:31 pm

On my Rowing Jon project, I intend to use a Bicycle speedometer pickup and display. It's about $20 altogether.
Down on the bottom, I'll make a plenum, sorta like looking at a water bottle laying on its flat side.
That will funnel the water to a paddle wheel.
That Plenum will protect the paddle wheel from my beaching's and when I Row through grass, Weeds n' brush.

garrys
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Re: speedometer

Post by garrys » Wed Aug 18, 2010 8:12 am

Go to www.livorsi.com

You'll find a great GPS based speedometer which has a traditional round gauge analog display for your instrument panel. It looks just like any other type of speedometer gauge. In my opinion, it's the only way to go. I installed one on my Monaco and am very pleased.

Garry Stout

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