Bad Powerpack ?

[76Red18]

Motor- 1999 Johnson 150 Ocean Pro Carbed 60 deg. V-6
Went out this morning and didn't even make it a 1/4 mile. Crusin @ 4500 rpm and motor slows down to high idle. Acted like the S.L.O.W. engaged but no buzzer and temp @ 165 which is where it normally runs. I shut it off and let it cool long enough for S.L.O.W. to disengage. I started the motor and still only could get 2200 rpm. I checked for spark from the plug wires and only have fire on the starboard cylinder bank. I checked all connections and grounds. About a year ago my buzzer and S.L.O.W. system engaged for no apparent reason and I've had no issues since then. Anyone ever had this problem? I think it has to be the power pack. Any input would be greatly appreciated. Thanks, Richard