RPM's

[B&J's94]

Which RPM source is correct? I have a '94 SN (351) with a 1.23:1 trans, also have Perfect Pass. With Perfect Pass on and set to 32mph the RPM reading from PP shows 3240, which I understand, the problem is that the Airguide speedo is reading 30mph, and the in dash Nuatique RPM gauge reads 3500. I know the speedo can be adjusted, can the tach be adjusted? I am assuming that the PP RPM reading should be the gospel.

Just purchased the boat, I know it has an OJ 4-blade, have not removed it so I am not sure of the size.

Where do I start to get all RPM readings in sync?

[Mikeski]

Don't believe the speedo or the teleflex tach, the PP is the gospel as you said. One problem with these teleflex tachs is that they are adjustable for 4/6/8 cylinder engines and sometimes they jump between modes. Mine does it about once a year, I have to pull the dash cap and futs with the adjuster until it makes a good connection in 8 cyl mode. Yours is just a little off. You may also notice that they are not linear.

[workky]

I dont consider the perfect pass to be gospell.I have a perfect pass.My rpm's are off and the speed is off.The faster i go the worse it gets.Perfect pass says wide open is 4600rpm's with a speed of 34mph,My airguide shows 42mph.It doesnt really bother me though i dont never really go that fast.But perfect pass is wrong.It starts at 25mph,and gets worse after that