Speedo Pitot Tube Replacement

[Jacalore]

Speedo doesn't work, checked out pitot tube, it's cracked on the end. Ordered another, replaced defective one. Q: Is the rubber hose length critical? The new pitot tube connection must be a bit higher on the transom, cause what was a straight run, now has to be rerouted to take up extra slack. I was gonna cut it, but two things - the end is flared and snaps onto the tube barb securely, may not fit w/o flair. And maybe the hose length is calibrated to the instrument?

 

[UncleWillie]

Re: Speedo Pitot Tube Replacement

The length and diameter of the tube absolutely do not matter one bit.
The tube just delivers the pressure of the moving water to the gauge.
Anything that is air tight will work.

 

[H20Rat]

Re: Speedo Pitot Tube Replacement

Nope, its simply the amount of pressure. In theory the longer hose will cause the speedo to respond slightly slower, but in reality, that delay is still faster than a boat can reasonably change speed, so it makes no difference.

 

[dccordell]

Re: Speedo Pitot Tube Replacement

The tubing length shouldn't matter.

Did the tubing come pre-installed on your pitot? All of the pitots I've replaced just came with a coil of tubing and I cut and installed it myself. The pitot has a tubing barb, as well as the speedo gauge. Is your's not like the one in this link: Faria Universal Pitot Kit - iboats

I'm guessing you used the existing tubing, and the end of the tubing has a permanent "flair" in it from the old pitot. If so, you should be good with cutting that end of the hose off, to the length required, and pushing the new cut end back onto the new pitot. Got pics?

 

[NYBo]

Re: Speedo Pitot Tube Replacement

Sorry, you guys are absolutely WRONG. Length of the tubing is absolutely critical: It has to be long enough to reach from the pitot to the speedometer or the speedometer won't work!:laugh:

 

[Scott Danforth]

Re: Speedo Pitot Tube Replacement

:facepalm:

 

[dccordell]

Re: Speedo Pitot Tube Replacement

Sorry, you guys are absolutely WRONG.:laugh:

Doh!! :der:

 

[Jacalore]

Re: Speedo Pitot Tube Replacement

The tubing length shouldn't matter.

Did the tubing come pre-installed on your pitot? All of the pitots I've replaced just came with a coil of tubing and I cut and installed it myself. The pitot has a tubing barb, as well as the speedo gauge. Is your's not like the one in this link: Faria Universal Pitot Kit - iboats

I'm guessing you used the existing tubing, and the end of the tubing has a permanent "flair" in it from the old pitot. If so, you should be good with cutting that end of the hose off, to the length required, and pushing the new cut end back onto the new pitot. Got pics?

Correct, I replaced the pitot tube on the transom only.

 

[Jacalore]

Re: Speedo Pitot Tube Replacement

Ahhh... Took her out today, speedo not working correctly. Doesn't register lower speeds only over 25mph... Maybe I should blow out the tubing with compressed air. Will that damage the dash gauge?

 

[smokeonthewater]

Re: Speedo Pitot Tube Replacement

you can't blow out the tubing unless you remove it from the gauge

you MAY have gained length by pulling a bit of tubing out of the boat to the transom and MAY have kinked it inside the boat.... Ya MIGHT consider just replacing the tubing while you are into it as you'll find it REALLY annoying if you keep messing with this for a long time and eventually find a leak in the tubing

 

[Scott Danforth]

Re: Speedo Pitot Tube Replacement

disconnect from the back of the gauge and blow it out. I usually turn the compressor down to about 25 psi for that.

 

[UncleWillie]

Re: Speedo Pitot Tube Replacement

Ahhh... Took her out today, speedo not working correctly. Doesn't register lower speeds only over 25mph... Maybe I should blow out the tubing with compressed air. Will that damage the dash gauge?

If it stops going up at 25mph you may have a leak in the hose that starts at ~8psi.

For your Reference...
1.5 psi = 10 mph
2 psi = 12 mph <<< Typical pressure produced by a set of young health lungs.
6 psi = 20 mph
13 psi = 30 mph
23 psi = 40 mph
52 psi = 60 mph

Notice that the scale is exponential; twice the speed gives 4 times the pressure.

 

[Jacalore]

Re: Speedo Pitot Tube Replacement

Thanks for the advice, I'll try blowing out the tube.

The symptom is that the gauge doesn't register until about 3000 rpm then it reads 25mph. No lower readings.

 

[smokeonthewater]

Re: Speedo Pitot Tube Replacement

could be that the gauge is busted too

 

[Jacalore]

Re: Speedo Pitot Tube Replacement

That's true, smoke.
I have a pressure gauge, if I add pressure at the transom end I should be able to read the gauge at the other, if so, then I would suspect the speedo. is there a better way?

 

[smokeonthewater]

Re: Speedo Pitot Tube Replacement

I suspect that you have a leak