Broken speedomoter

[sparky27]

My speedometer recently quit working. The needle is stuck between 10 and 20 mph, the backlight still works. Any ideas or advice on where to start troubleshooting would be great. Thanks.

[mudslinger]

What is the speedo on??? and does the needle move or is it just at like 15.5mph?

[boatfixer]

Look at the back of the speedo. Remove the tube from the center of it and see if the speedo returns to zero. If it does, blow back through the tube, it may be plugged. If it does not, then it sounds like you may be in for a new speedo.

[sparky27]

The needle is just stuck, does not move at all. What holds the tube on the back of the speedo? Do I need to remove the speedo from the console to remove the tube?

[sparky27]

Also what is the function of the tube?

[boatfixer]

The speedo works by air pressure. As you move forward in the water, water forced into either a hole on the leading edge of the gearcase or into a pitot tube attatched to the back of the boat. This results in air pressure in the tube that runs to the back of the guage. The faster you go, the more pressure. This pressure acts against a spring inside the guage. The tube is just pushed on and maybe secured with a wire tie or small clamp. In most cases, you wouldnt need to remove the guage.

You either have a bad guage, or there is something blocking the tube or pick up somewhere and not allowing the guage to return to zero. Try unplugging the tube first.

[sparky27]

Thanks for the advice. I will have the boat out this weekend, I will then know if the speedo is again working properly.

[hydro]

You probably got some water in the tube last year and it froze over the winter. The needle position is the symptom. If so, it is ruined and time for a new speedometer.

[propster]

Find the (usually) black rubber hose down along the motor somewhere and hook up air compressor to it and blow thru, see if needle jumps. If not you may have obstruction or break in line.

[minneman]

Ive got a similar problem except that the speedo when not moving reads 45mph, yet when under way works or atleast goes up the dial but zeros at 45mph. I had the back of the speedo exposed and didnt find anything that changed the problem, any ideas?

[boatfixer]

If the needle is stuck in that position yet moves when underway, then the problem is most likely the guage itself. If it did not move at all I'd tend to think it is an obstuction as it wouldnt be letting air in or out. A common misconception is, is that water is forced all the way to the speedo head when it actually only can go part way. Air pressure from the water being forced into the tube is what is acting on the spring inside the head. The system has no "vent" and therefore if your pick up tube became plugged underway, it would not be able to releive the pressure in the line, allowing the needle to return to zero. Since your needle will move, The problem more than likely is the head itself.