speedometer
#2
Gold Member
Gold Member
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.
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.
#3
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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
least fool me to make me think my boat has more power.
thanks
#4
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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
least fool me to make me think my boat has more power.
thanks
#5
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.
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.
#9
Gold Member
Gold Member
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.
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.
#10
Offshoreonly Advertiser
Offshoreonly Advertiser
Speed = 8.31 x sqr rt of the pressure, 100 PSI = 83.1
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Marc
www.mercruiserparts.com
www.go-fast.com
www.bammarine.com
www.cyborgtransmissions.com
It's not alive -www.BoatStuffExpress.com - temporarily retired