sounds like you were in the rev limiter. what rpms? a larger pitched prop or lowering the engine will cure. in addition, running in cool weather = more horsepower and the rpms will be greater than when the spring and summer get here.
i have a 06 sabre with mercury 150 efi i keep hitting my RPM rev an im not even trimmed a quater up on my guage i have a Tempest 24 pitch prop should i drop my jack plate or bigger prop