Two speedometers using one water pickup?

[Bradz]

I was hoping to rig two water speedometers off of one water pickup. Will that work or would it lower the pressure somehow and cause a lower reading? It is an older Gaffrig by Livorsi setup with the large 1/4 water hose. I was going to run a tee fitting.

[MOBILEMERCMAN]

I can only guess. I suspect it will work. A gauge doesn't alter pressure.

[old377guy]

should work

[Ted]

Should work, but will not be as quick to respond since it will take longer for the pressure to build up. But after a short bit the pressure will equalize. Pretty sure some of the old ski boats did this.

[cigdaze]

It will work fine. Pressure's pressure, doesn't matter if it's split or not.

[Knot 4 Me]

Sunsation does this on their MCOB boats.

[Bradz]

Thank you everyone. I was also told that instead of a tee fitting a Y-fitting might be better for the flow.

[glen george]

I did this a while ago using a T fitting, there within 1 mph gps , looks cool also.

[jeffswav]

Water pickup speedo's suck, I like to know the truth. GPS is the only accurate way for boats. Just my .02

[bajabob 718]

Water pickup speedo's suck, I like to know the truth. GPS is the only accurate way for boats. Just my .02

i agree with jeff i test all my props and any add on with gps . now my speedo only go to 80mph so when i go past 80 the needle goes crazy

[gcarter]

A good Bourdon tube type, pitot fed, liquid filled speedo will be nearly as accurate as a GPS for a fraction of the price. The ones that I have used always recorded within 1 or 2 MPH of the GPS.
A speedo of this type must have a range quite a bit higher than the expected speed, so an 80 MPH boat should have a 120 MPH speedo for instance. The ideal would be where the range of the instrument is about 40% higher than the expected speed. As pressure increases, the Bourden tube slowly unwinds and the very delicate gear train and linkage moves the needle. If you're operating near the end of the range, the movement mechanism will be jammed, and maybe destroyed.
I had lunch yesterday w/a friend at the Mt Dora/Tavares Fl Antique Boat Show who is on his third GPS speedo...something is always failing. A good Bourdon tube speedo should last almost indefinately.
There's no water movement within the gauge or the plumbing. Since water is virtually incompressible, there's no place for the water to go. All the pressure does is unwinds the tube. The displacement doesn't change. As many gauges as desired can be plumbed up. Heck, put some in the front seat backs for the rear seat passengers to use.

[MOBILEMERCMAN]

I agree a good liquid filled measures well. I find it common for them to read 1 mph slow.


The gps vs speedo discussion should include speed of the boat. At 100 mph the speedo can actually begin to have an noticeably effect on speed.

[BBB725]

At 100 mph the speedo can actually begin to have an noticeably effect on speed.

and the pocketbook

[Chris]

If you can look at the speedometer, you're not going fast enough.