How Accurate Is a Stock SpeedO
 

Any one have any idea

Re: How Accurate Is a Stock SpeedO
 

Its not accurate. But, then again, neither is GPS. Thats gonna start something here..

My Livorsi speedo says 85, gps says 80

Re: How Accurate Is a Stock SpeedO
 

Believe the GPS. Never believe a stock speedo. They are always fast. There are other variables with a GPS and maybe radar is the most accurate but GPS is the best we have to install in our boats.

Re: How Accurate Is a Stock SpeedO
 

I find my speedo is very accurate..within 1mph of my gps.

Re: How Accurate Is a Stock SpeedO
 

My stock speedo is 8 mph off at 2,500 rpms and 4 mph off at 5,000 rpms. too high!!!!

Re: How Accurate Is a Stock SpeedO
 

They are all off at various points. Each boat I have owned has been correct or off at different speeds. No rhyme or reason!

Re: How Accurate Is a Stock SpeedO
 

I call the stock speedo's passenger thrillers, my last boat did 10 over at WOT. My 22 is very close at all speeds which still surprises me.

Phil

Re: How Accurate Is a Stock SpeedO
 

Most speedos are very optimistic. However, I have a customer that I built an engine for that went from 58 to 73 on GPS. However his stock speedo read about 5 MPH slow. Man, that was just not acceptable! So, we installed a GPS analog speedo. That is the only stock speedo that I've ever seen read slow.

Re: How Accurate Is a Stock SpeedO
 

I didnt mean to start anything bad here... lol... but it sure seems that i am going alot faster than 60 in my scarab

Re: How Accurate Is a Stock SpeedO
 

Here is a formula that most use to calculate speed.


((pitch x rpm) / ratio) / 1056 = theoretical speed. Then you must allow for your slip %.