Speedometer Upgrade

[bkdlays]

Is this a standard speed sender? Can I replace the gauge with one that starts off slower?

The sender seems to be a little white tab that hangs off the stern near the prop.

Where do I start with replacing the unit? Are new ones electronic? Thanks

This one wasn't working, but I noticed the hose fell off of it.. so thats probably why.

 

[Hit It]

Re: Speedometer Stopped Working

Re: Speedometer Stopped Working

That white tab hanging off of the stern is a pitot, which is hooked up to a hollow rubber tube which runs from the stern to the back of your speedometer. I believe that the system works on air pressure. As the pitot off the back of the boat passes through the water, air is forced into the tubing, which causes the speedometer to register a speed.

The tube sometimes get plugged up or kinked. Inspect the tubing for kinks and maybe disconnect it at both ends and force some compressed air through it to clear any obstructions. Also check that the white pitot on the stern is in to the down position. It is designed to flip up if it hits some kind of obstruction in the water. Sometimes the little hole on the bottom of the pitot gets plugged up as well.

These speedometers are not very accurate. For a more accurate speed reading, I would use a GPS. There are also speedometers that use a paddle wheel type sensor on the stern of the boat, not sure if these are more accurate and less prone to failure or not. I know that my fishfinder has this option.

 

[tashasdaddy]

Re: Speedometer Upgrade

that is call a pitot. the speedo works on air pressure in the hose. as the boat moves forward, the water puts pressure on a small hole in the pitot, pressurizing the hose, which activates the speedo. there are GPS for electronic readings. the reason they only read above 5-10 mph, is not enough pressure to activate.

 

[QC]

Re: Speedometer Upgrade

You can test by blowing into the tube and if the needle on the speedo moves, then it works . . .

More accurate speedos use a paddle wheel type deal that sends electronic pulses to an electronic speedo. Very common setup with depth sounders that have speedo capability, but you can also buy typical gauge type setup with the paddle wheel. Very accurate at low speeds.

Also, there are GPS speedos as mentioned above, but they only record speed over the bottom . . . will not be accurate for speed over the water if there is any current.

 

[fishingdan]

Re: Speedometer Upgrade

As noted above, the speedos that depend on water pressure from a pitot are not generally that accurate. Temporarily I have two boat in my driveway. One's speedo is typical in that it is somewhat accurate between 22 and 45mph. Outside of that range, it is way off. My older boat has a speedo that is spot on from 5 mph and up per gps.

The paddlewheel speedos that I have had tend to be more accurate at the lower ranges, but less accurate above 30mph. These are adjustable, but when you fix one range, you lose the other.

The key question is what "needs" do you have for the speedo? For example, do you want accurate trolling speeds for fishing? If so, you want something that is accurate water speed from 0 to 10 mph.

My suggestion is to get the speedo you have in place working and then supplement it with another unit that meets your needs (GPS or paddlewheel type).