Opti bucks at high rpm

[nathanhenry86]

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If I run wot the motor will buck like its running out of fuel I can't figure it out!
Some history:
I had a bunch of water in the tank and it took out my high pressure pump, boost pump, and 2 direct injectors. I put a new diaphragm kit in the pulse pump and sent my rails to have all 3 regulators replaced. I also installed new fuel likes, primer bulb, removed the anti siphon valve and put brand new racor water separator and replaced the one on the motor. The racor is new (my boat didn't have one before). My fuel pressure on the rails is 90 psi air is 80. I've swapped pick ups on the tank. Only 1 dtc something like sea temp?

I'm planning on checking vacuum at the primer bulb while running.
Any help would be great!

[LIQUID NIRVANA]

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If I run wot the motor will buck like its running out of fuel I can't figure it out!
Some history:
I had a bunch of water in the tank and it took out my high pressure pump, boost pump, and 2 direct injectors. I put a new diaphragm kit in the pulse pump and sent my rails to have all 3 regulators replaced. I also installed new fuel likes, primer bulb, removed the anti siphon valve and put brand new racor water separator and replaced the one on the motor. The racor is new (my boat didn't have one before). My fuel pressure on the rails is 90 psi air is 80. I've swapped pick ups on the tank. Only 1 dtc something like sea temp?

I'm planning on checking vacuum at the primer bulb while running.
Any help would be great!

Was Ethanol the culprit?

[Pullhard800]

My 05 2.5XS did the same thing, mine was due to the extra filter. I had the one under the cowling plus a water separator and it was starving for fuel. Took the water separator off and runs perfect since. Not sure if thats your problem but the two filters were too much for mine. Hope this helps. Called a performance dealer and he said the one under cowling was enough!!

[nathanhenry86]

Yea it separated and the alcohol destroyed things

[nathanhenry86]

this thread was longer and I had more posts what happened?

[prosken300]

It can be a bad bobine or sparkplug, have encounter this more on optimax engines.
With the mercury cds program you can cut off the ignition cilinder per cilinder, if the engine quits bucking that is the bobine or sparkplug you need to replace.
This test has to been done while running the boat on the water in the rpm range you have the problem, did you test fuel and air pressure ratio on the water also?
On the hose, running @ idle pressure can be good, but under load not.

[nathanhenry86]

I fixed it there was a peice of plastic stuck at the float in the vst

[XstreamVking]

Some of the toughest to find problems have the most simple solutions. Good job finding it.....