powersurges over 3500rpm

[popobowa]

Good day youall!
I've got a 1996 150hp 60deg ois2000 Evinrude (live in Africa) and keep having power problems with it.
I have done the following maintainance:
-cleaned carbs (attached portable fuel tank)
-changed CDI/ optical sensor/plugs/leads/ coils and stator. Rectiier works and doesnt interferre with rf noise

-the engine starts immediately, Quickstart works, idles well
-when I apply throttle too fast it doesnt pick up power well (allthough better after chg of electronic parts)..have to "milk" the throttle upwards.
-from 3200-4000rpm the engine doesnt seem to deliver more power in spite of increased throttle, but does surge 200-500rpm at times. Best rpm I get is 4500...it used to go up to 4800-5000 @ 37kt...now max is 32kt. At this speed fuel consumption is high and plugs tend to stay wet. If running at 3200-3500, plugs stay dry....black to dark brown.
It just doesnt make sense to me...anyone with experience to give a hint?
I dont have any technical support down here at all.

rgds
Stefan

[boats.net]

Check compression to make sure all cylinders are even. Check timing may be a problem with timing wheel on flywheel. Most of the time surging is a fuel related problem, do a fuel pump vacumn test and fuel pump pressure test to see if getting enough fuel to carbs. Look for air leaks on intake manifolds.

[popobowa]

Thanks for the hints......i cant chk compression here at the moment, but when I had the cyl heads open the sleeves and rings seemed like new..as the first owner claimed (with paperwork ) that he'd only done 80 hrs on the engine, and I have since done app.100hrs. rings have no play restriction and float freely.

Timing WOT is 20degrees

carbs and throttle body are clean...was a bit of dirt in the throttle bodies (like fine rust)
I installed an extra fuel pump just in front of the rubber ball pump...and now get the engine revs to 4000-4200rpm but not higher..the engine takes throttle much better though.
I forgot to mention the first time that the "chk eng" light is mostly on...but it stays like that after turning on ignition...without the engine even running. According to manual that means fuel or ignition problem. Without a fuel pressure gauge..how do I judge the correct fuel pressure? I guess after VRO pump?
rgds
Stefan

[boats.net]

Try pumping primer bulb while running to see if rpm's increase.

[popobowa]

Ballpump stays hard due to inline fuelpump installed. Still dont get more than 4000rpm , sometimes only 3500. ChkEng light mostly on ,sometimes accompanied by constant warning tone.

Just cannot figure it out, cant be a big problem!