Please Help Need Advice on 05 225tlr hpdi rpm fluctuation

Hi,
new to me, 225 yamaha hpdi 2005 model with less than 100 hours on a Champion 198 elite.

Here is what i have done so far to remedy my issue.

Boat Fuel water sep. replaced.
Port Side External paper filter on engine replaced.
VST Filter Replaced
Strainer replaced
Fuel Reg. screen inspected.

Drain tank and running ring free with no ethynol fuel. (87) octane

WOT=5600rpms
Prop=26p Tempest Pro appears to be out of box and know that this is an issue and we are switching to a 25 pitch to get closer to 6000 r's


Okay, here is the problem. The rpm's are steady as a rock everywhere except wide open throttle. When WOT the r's drop and vary about 300 rpms. It does not appear to be skipping but, but, but, the typical 198elite runs 74mph with tourney load at peak perf.

We cannot pull more than 67mph with mild load and 20 gallons of fuel.

The jackplate is a 10" slidemaster manual.

The previous owner had it 4-1/8" BP

I have raised it to 3" BP

The boat runs the exact same mph and rpm as it did before making one change!! Seriously, no performance enhancement at all. I thought the jackplate alone would have gotten me something since it was so so low in the water

Any help on this issue will be greatly appreciated. I started a thread in the bbc forum under Yamaha and under Champion forums and you can see the track I have been down to get here!

Please Help!

P.S.--thought it might be running lean or may have load problem so today we dropped the trim all the way down and held it at WOT and the r's never rocked on penny.. Steady at 4400 rpms but raise the trim and hit the high mph and we have the problem again.

One other thing, the boat is steady no chine.

[boats.net]

have your dealer run a computer diagnostic on it. The ECU may be adjusting the timing based on sensor signals like knock sensor, if engine is knocking it will reduce timing until knock resides then will advance timming.
The computer will show high fuel pressure if there is a fuel restriction in high pressure pump.

05 225 hpdi rpm fluctuation engine problem

thanks for the advice. We have to take it in next week to have the oil pump recall done so we have a list of things for them to check out and i will add this to our list!!

Thanks