power gone from my 8.2 mercuiser
 

we have a poblem with a 8.2 mercruiser, computer say everithing ok , but we mis 600 rpm at wot.
changed spark plugs , measured fuel presure 40 psi , must be 43 psi . so changed fuel pump, and regulator, still the same problem.
can the cause this problem, 3 psi diference ?
sugestions are welcome.

What tach are you using, and do you know it's accurate? The boat tach's can be off by 5 to 10% at WOT. Are you getting all your advance? What system are you using, MEFI (what), MSD, etc?

not enough info here which 8.2 the newer cat engines or the later ones with MEFI. Year and engine serial # helps plus will determine what fuel system set up you have along with what fuel injectors were used.

Just a guess here - you can have good fuel pressure but the fuel injectors can be the problem and or their spray patterns for performance issues & loses.

Compression and leakdown #'s and a fuel vacuum test ?