Friend of mine has a 25 outlaw with a 496HO stock setup. On a normal day you can push the throttles forward and run all day long. All of a sudden he said he started to hit the rev limiter which never had happened before. Now the boat can only get to the 3/4 throttle before hitting the limiter. RPM's and speeds are all normal.

Was told it wasn't linkage or coupler.
Prop is in good shape. No signs of dings, nicks?
Any ideas? Could props blades have warped, etc to a point where it can increase RPM's?

If the prop has a rubber coupler, they can spin as the load increases. This could the reason for the same speed but more RPM.

Sounds to me like a valve train issue, maybe broken spring(s).

How can he be hitting the rev limited now even though the RPMs are the same?

Are we just talking throttle lever position like when you run in cooler temps, motor runs better?

the RPMs have to be increasing, otherwise how could it possibly be hitting the rev limiter?

I agree with the prop hub possibly spinning, although they usually will spin when getting on plane if they are going bad.

mark the prop and hub and see if the marks stay aligned. Coupler is a little harder to check but I've been told you will smell burned rubber if it is slipping.

I interpret his post as the rpm and speed are in-line but low due to what seems like rev limiter action.

That's right. Is he actually hitting the rev limiter or is the motor breaking up - which sounds like hitting the limiter?

Maybe guardian mode. Good clarification, not prop hub or coupler then. The engine gurus here will know .

correct. check that first. You can do it yourself and it's an inexpensive repair if necc. go from there