2017 115 Mercury ProXS High RPMs

Mwalls

Recruit
Joined
Jul 22, 2018
Messages
1
For the past 3 months my engine has been running at high RPMs (7000) when wide open and trimmed up. I have a Ranger RT198 aluminum boat. Normal is around 5800. I had the boat in the shop and they can’t find anything wrong. It started surging on me yesterday. Everything is still set at factory settings. No jackplate and it came with a 24p 3 blade prop. Any suggestions or thoughts is appreciated. I’m not sure what to do from the point. We are going to drain the tank to see if I may have gotten water in it, but still can’t explain the high RPMs. Running non-ethanol fuel too.
 

schematic

Lieutenant Junior Grade
Joined
Jan 12, 2008
Messages
1,102
best be checking the prop hub. Mark the nut and the blade assmy. and watch for misalignment after a run...
 

Alumarine

Captain
Joined
Feb 22, 2005
Messages
3,757
Is the speed greater at 7000 than it was at 5800?
Have you tried a different tach?
The shop can check to see what the ECU has registered as the maximum rpm it has run.
 
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