RPM Fading

[Groovius]

Interesting problem with my 1999 VMAX 200. Finally have it proped correctly. On throttle up, engine will ramp up to 6000 RPM, then after about 3-5 seconds, it will fade down to around 5000 RPM, and then jump up and down 300-500 RPM until throttle down. It will run smoothly all the way up to 4500 - 4800 RPM, then begins stutter as if it is momentarily fuels starved or spark is getting retarded.

I can back down to idle, idle along for a few minutes, throttle up to 6000 PM again and start the process all over.

Very odd. Any thoughts? BTW, thanks for all the commentary on my previous thread for not developing full RPM, I finally changed from a PowerTech ELE 15 pitch 4 blade to a PowerTech WBB 12 pitch 3 blade. Made all the difference in the world.

G

[99yam40]

monitor high and medium fuel pressures at the same time as problem is happening to see if there is some pressure drop from restrictions in the filters and screens