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Old 24 August 2014, 18:26   #1
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Country: USA
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Boat name: Clear Cut
Make: Polaris
Length: 6m +
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Yamaha speed gauge reads "-"

Since I've had the new motor the speed gauge reads "-" at speed and the trip odometer stays at zero. I've disconnected the tubing from the gauge and blown compressed air through the tubing. My wife reports that the air coming out at the pitot tube on the lower unit is "forceful". The gauge shows numbers when blowing into the tube on the gauge side. I've been fiddling with this off and on for most of the season.

If it still doesn't work on the next outing, is there anything else that I am missing? The only thing I can think of is that there is something in the tubing that is acting like a one way valve.
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Old 24 August 2014, 19:37   #2
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Well, it's simple to disconnect at the LU and blow air back up towards the gauge. There's usually a service loop of tubing sticking out about halfway up the leg.

As far as what else; I can't think of anything. You could use plasticene or the like to seal a piece of tubing to the pitot hole and raise a container of water higher than the disconnected gauge input and see if water makes it the other way.

The amount of pressure generated, I suspect, is pretty small (how much pressure will be generated by a .030" hole moved through the water at, say, 5 mph?) Could be a faulty gauge.

jky
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Old 28 August 2014, 12:31   #3
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Country: USA
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Thanks for the ideas. Your plasticine idea is brilliant, would not of thought of that. Still have not gone out since I did the testing, but if it still doesn't work I'll give it a try.
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