prop serios question please help

[PERIKO]

i have a 90 hp force 1990 non thru exhaust,my aluminum prop is 13x19 cupped,i bought a 13x19 cupped stainless steel prop and instead of my rpm being5300 like it was with the aluminum one its 7500rpm with the ss one,can my tiny tach be mess up,i dont have a rpm gage only a tyny tach????

 

[PERIKO]

Re: prop serios question please help

by the way its 35mph with both prop,,,aluminun and ss,that means its not slipping,its a brand new ss prop

 

[Silvertip]

Re: prop serios question please help

The sensor lead for the Tiny tach is picking up signals from another cylinder or there is some electrical noise its picking up. If the speed is the same with both props the issue is with the tach.