I have a new teleflex speedometer. I is off about 4 mile an hour slow. How do i recalbrate it?

thanks

Not sure if it can be done

Check the back for an adjustment point, maybe a hole where a small screwdriver can be inserted.
But the first thing you need to find out is if the error is the same over a wide range of speeds (linear). Check the indicated speed against a GPS at 10 MPH increments (10,20,30,40,etc.).
If the error is less at slow speeds and worse at high speed you'll have to pick a mid point and make that indication correct, split the difference or average it out.


Since a marine speedometer is operated by the flow of water against the pitot creating air pressure inside the tube the readings may be different each day. Different water and atmospheric conditions have an effect too.

Good luck.

I don't see anyway to adjust the speedo in the back. Wonding if the pickup chould be mounted wrong? I would rather have it read fast than slow, maybe it would at
least fool me to make me think my boat has more power.
thanks

I don't see anyway to adjust the speedo in the back. Wonding if the pickup chould be mounted wrong? I would rather have it read fast than slow, maybe it would at
least fool me to make me think my boat has more power.
thanks

Some new boats are coming out with Speedo's that are way off (usually fast)

You should have it mounted in a area where it can get clean water. Nothing in front and not near a chine. Either of these affect water flow.

The other possibility is the angle of the pitot is not correct.

my vdo is reading 6mph fast needless to say when I saw reality on gps I couldn't stop crying

Check to see if your pickup is partialy plugged. I've had that with a Bravo. There had been a piece of wood in it and it hadn't all been cleaned out.

I have a new Gaffrig GPS speedo, and I think its 4mph slow too. Maybe I can contact the government and they can adjust it? Wishfull thinking

I calibrate instruments and there aren't many gauges that can't be adjusted.
Never really looked and one but will the back of the gauge come off? If so, then maybe there's an adjustment point inside.

Sone one once posted a way to bench check a speedometer using compressed air. I don't remember what pressures created the indicated speeds.

Speed = 8.31 x sqr rt of the pressure, 100 PSI = 83.1