2000 250 hp saltwater series

"I need some help with a issue

"I need some help with a issue with this engine.It is a intermitent problem of loss of RPM, does not go below 4200. Will drop from 4600 or 5000 to 4200. Some things I have done
Ran on seperate tank
Changed the VST filter
Have water seperator, always clean
Have done fuel pump diaphrams.
Changed plugs
Ran ring free through system
Checked compression all 110
Checked fuel pump pressure 35psi.
Ran new fuel line
new primer bulb.
New fuel filter
Checked CDI for code with winky blinky,none found
Is there any way to check coil. could this be a coil breaking down.
What about a injector and how do you check
Please help"

"Check for loose throttle link

"Check for loose throttle linkage on one or more cylinder?

Double check plugs for evidence of fouling or water intrusion.

Sure sounds like fuel pump problem to me.

Oxygen sensor ever been cleaned or tested? I know it shouldn't cause the symptom that you described, but I do know a case where a new O2 sensor fixed that exact problem (at least that's what the guy claimed). I did my fuel pumps and O2 sensor at the same time when I had that problem, but I suspect fuel pumps were main cause."

Ken:
I recently purchased a b

Ken:
I recently purchased a boat with the same motor and it has the same problem. At about 4200/4400 RPM it wanders up and down about 200RPM. Compression all good and fuel pumps are new. Water separator clean. I'm going after the VST filter next. Did you ever find your problem? I will keep you advised on my progress.
Mike