2001 Johnson 225 HO won't go past 5000 RPMS

[S_Miketa6]

Hello I have a 2001 Javelin Renegade 20 with a 2001 Johnson 225 HO. The motor had a new powerhead put on this past September, since the new powerhead has been put on it has been running fine and up to 6000 rpms easily. Up until a month or so ago when it would not exceed 5000 rpms. When taking off it jumps out of the hole fine, excels and builds rpms but will get a hair over 5000 rpms (roughly 45mph) then drop down and will not exceed that until taking off again.

The boat has been taken to the dealer who has a lot of experience with Johnson/Evinrude. They ran compression tests, checked timing, checked fuel system, throttle linkage, operation of carbs and it all checked out with flying colors. I have not changed any fuel lines or the ball or fuel filter, I have changed the plugs. Everything to me points to some sort of electrical issue or sensor but was told there is no speed sensor on these motors. The power pack has been changed a year or two ago for a separate issue but not sure if that could be something causing the issue also? This is still the original lower unit and have had no prior issues with it, I am running a 23p Renegade Bass Prop about 3.5" prop to pad height if I remember correctly. I do not feel this is the issue because the boat has been performing per the course until a month or so ago. Not really sure where to go from here, as I have said aside from this issue the motor has been performing great prior and still is with this issue occurring.

Any suggestions or information will help, I may just have to wait and take it back to this prior dealer or to another for a second opinion because it seems to me like a minor issue that could be holding this up. Let me know what you think. Thanks!

[JER-1 BIG BASS]

Outside temperature could have a little bit, go ahead and put an oem new ball on it , made world difference in mine.
And if that helps , maybe knock out the backflow ball in fuel line , can’t think the name of it, where it goes into tank, that can restrict fuel flow, and while there just put new marine grade 3/8 fuel line from tank to ball.