78 1150 mercury cant reach rpms help!!

[1150 mercury]

I have a 78 mercury 115hp 1150 i cant reach 5000 to 5500 rpm ive tryed 3 props started with 21 and went down to a 17 the most rpm at full throttle iv been able to get is 4400 i know my motor should get up to at least 5000rpm. its on a 18ft 1969 stylecraft speed boat i wanna use it for wake boarding and haullin but across the lake. I JUST BOUGHT THE BOAT LAST MONTH. I WAS TOLD IT RAN GREAT IT SEEMS TO RUN RELLY SMOOTH IVE PUT PROBABLY 10 15 HOURS ON IT SCINCE IVE OWNED IT.NO PROBLEMS EXCEPT RPMS, RPM GUAGE WORKS FINE

 

[Spidybot]

Re: 78 1150 mercury cant reach rpms help!!

To give us a better chance to help, could you state what boat, running rig weight, use of boat, how it ran previously, if your tach is likely showing the actual rpm, if the motor is well serviced (sparkplugs) and what you've done so far to troubleshoot it?<br /><br />Do you own a manual? If so, did you do any of the described tasks to identify the problem?