looses power at WTO when triming engine.

[Frank A]

this past week has been the 1st time Ive not used double oil since engine rebuild was completed. I had a lose of power on top end around 4800 to 5200 rpm. I must still have a base engine problem cause its doing the same as before I lost a piston and had to rebuild in May. Its just has not been felt because Ive been doing the double oil and low rpm BREAKEND route.
Last week was 1st time I've ran with out double oil and trimed it up at WOT I felt slight flutter and lost little power when full speed full trim. I eased out of the throttle & trim down alittle ran fine under 4500 rpms.
I checked plugs were no signs of runing lean,( I installed larger jets during rebuild so it would not run lean) all looked good!I elected to replace them since they were run and idled alot during engine breakin. I have changed water seperator filter and checked the engine fuel screen recently.
I went out again Saturday ran strong till full trim wot. It loose power and accleration became mushy/flat, like running out of fuel psi. ease out throttle and ran fine. I have had a vro/fuel pump go out before. iThis did not feel like that. when that happened the engine would cutoff unless someone pumped the bulb. I did notice the engine does do the heat soak thing. At times has a hesitation just after planing off which you just drive thru and during 1st acclerate in gear after engine has been driven and warmed have to push the choke to keep it from cutting off . For last 12 years. I never noticed ether of these sympthoms.
I was wondering if possible the diaphram could be going bad on the fuel side of the vro? Thinking about putting a electric regulated fuel pump in the fuel line then go run it to see how it acts.
WHAT YOU THINK Fred!

[ChampioNman]

Anytime you go up on your HS you need to compensate on your idle and intermediate jets. The HS don't kick in until you get in the upper power band so you have to transition the other jets too. Knowing how to read plugs and playing with the jets is a difficult thing.

[Frank A]

Dont think its a jet problem.......it was doing this before I replace HS jets acts like fuel restriction or low fuel volume at the higher rpm. but makeing me scratch the old head as to why it only felt when triming up that last little bit of travel and rpms above 4800? Possible related to voltage drop ro carb level?

[ccuboy123]

sounds like a power pack

[SEAHORSE]

A weak stator can give similar symptoms

Even if it tests OK with a meter, inspect both sides of it for melted insulation around the charge and power coils.

[Frank A]

CCUBOY123----replaced power pack with know good unit and ran some Friday night. I could not get to top speed full trim for a long period of time but did get there a couple times for approx 2 minutes each time it seemed ok. Wille try to goet a better run one evening this week when lake is not so rough and let you know.
Seahorse------I'll also include my voltage on my gps and monitor voltage out while running in case it acts up Ill be able to glance at the output.....
Another thing------- I sure hope its the 100 degree hi humity but can't turn my raker but 5200 usually not a problem to get 5600 rpms.

Thanks!

[Frank A]

2 time out ....has not acted up since power pac replacement.