MPH not showing on Gage OX66 motor

[crazy charlie]

2000 200hp Saltwater series with digital Yamaha gages.Everything else seem working.

mph has worked forever.Where to start looking.I did a water pump service this spring and attached the tube properly and has been working for approx 1 month this year.Any suggestions??? This is the style of gage right next to it..Thanks Charlie

 

[99yam40]

sounds like the hole in lower unit plugged up or you have a broken or plugged tubing leaving the motor heading to gauge. disconnect to tubing leaving the motor and blow into it with your mouth to see if the gauge responds
do not use compressed air,it can be too much and mess up the gauge

 

[crazy charlie]

Thanks!!! Not exactly sure where the tube leaves the motor??

 

[cyclops222]

Time for a FREE question to your Yamaha dealer on where the Lower Unit inlet converts water pressure to a electrical signal. It could be done right in the Lower Unit. Or tubed up to the powerhead of the motor.

 

[crazy charlie]

Time for a FREE question to your Yamaha dealer on where the Lower Unit inlet converts water pressure to a electrical signal. It could be done right in the Lower Unit. Or tubed up to the powerhead of the motor.

Im thinking powerhead since the pickup tube hangs from the leg when the lower unit is dropped and reconnected when lower is installed.

 

[boscoe99]

Water pressure is applied to the speedometer. To a nipple on the back of the speedometer. Within the speedometer itself the pressure is converted to speed.

 

[99yam40]

on my C40TLRX it comes out of the lower unit and runs up the front of the leg and over the T&T upper pin where it heads to the front of motor where it should be easy to see where it hooks into a small hose heading to the gauge wherever you have that mounted.
if yours is something electrical running to the gauge, then there will be a device under the motors cowling that would convert the pressure to electrical signal

 

[crazy charlie]

OK, thanks guys!! I'm looking...Charlie

 

[crazy charlie]

Didn't do much but flushed the motor thru the flush hose and now the mph is showing at 5-6 mph regardless of my speed.. at least its registering something????? Charlie

 

[dingbat]

Funny as it sounds, pivot tubes work on air pressure, not water.

Water does not compress. Any water trapped in the line will affect gauge reading.

Suggest removing both ends of the tubing and blow out with compressed air. If that doesn’t restore functionality you have a problem with the pressure transducer

 

[crazy charlie]

Funny as it sounds, pivot tubes work on air pressure, not water.

Water does not compress. Any water trapped in the line will affect gauge reading.

Suggest removing both ends of the tubing and blow out with compressed air. If that doesn’t restore functionality you have a problem with the pressure transducer

Thanks I will take a look. Do you know where the pressure transducer is exactly?

 

[boscoe99]

Pitot tube.

Water compresses but barely so. Water pressure in the Pitot tube is converted to air pressure which then causes the needle or digits on a gauge to change.

 

[boscoe99]

Thanks I will take a look. Do you know where the pressure transducer is exactly?

Transducer (or pressure sensor) is located with the gauge itself.

 

[boscoe99]

https://www.veethree.com/wp-content/uploads/2021/01/Trouble-Sht-Pitot-Speedometer_R4.pdf

 

[crazy charlie]

https://www.veethree.com/wp-content/uploads/2021/01/Trouble-Sht-Pitot-Speedometer_R4.pdf

Good info!!! thanks