Motor wont go over 5000 rpm

Hey guys. First time posting here. I have an 18' angler 180f with a j90plstc that I bought from a friend about 6 years ago. It was too good to pass up. It came with a 21 pitch prop from the dealer. It has never ever reached 5500 rpm since I've owned it. I have tried everything from a 19 pitch to a 13 pitch prop. I have replaced all fuel lines from tank to engine, fuel filters and housing, also primer bulb with omc, also the fitting at the tank which is not an anti siphon valve. Also cleaned the tank. With a 15 pitch prop it will reach 5000 but it will buck and sputter randomly. All carbs have been rebuilt with omc kits. Float level and drop within spec. The vro has been replaced with a conventional fuel pump. I pre mix.50.1. Timing is set at wot with an easy timer at 20 degrees at wot. It idles just fine. Wot is not right. Compession check is 135 psi all cylinders. Like brand new.. Spark jumps 7/16" bright blue on all cylinders on the hose.Wondering if I might have a power pack issue. I have a dva and the tools to test it and a factory service manual. Just not sure where to go from here. Any suggestions? Thanks in advance!

Have you tried a different tach? The fact it starts bucking kinda tells me you have a rev limiter.

I have replaced all of the guages, including the tach. Even compared the new tach to an inductive attachment on my multimeter. It is spot on. That's why I'm wondering about the power pack. I know it controls the rev limiter. I'm open to any insight. I'm a 20 year mercedes benz master tech. But this is a whole different ball game for me.

Also the sputter is totally random but worse and more severe at wot.

Does your motor have the optical ignition?

Yes sir it does. I have replaced the optical sensor with an omc replacement.

Have you done a link and sync? Are all the carbs opening all the way? Your #s are strange a 90 hp motor should sling a 15" pitch prop pretty easily. Otherwise start testing the ignition. When you swapped out the VRO pump for a standard pump did you take out the pulse limiter?

Flyingscott yes I have. I have triple checked the link and sync multiple times by the book. The carbs are definitely opening all of the way open. I did remove the pulse limiter during the conversion. It had no restrictions so I reinstalled it.

What about the pulse limiter?

I removed the pulse limiter. Inspected it. Zero carbon build up. Looked like brand new. I could blow through it both ways. Not sure if that is correct. The factory manual is pretty vague on that. It did have a white flap inside. I reinstalled it. Not sure if that was correct or not

You cant use that with a standard pump. Either drill it out or put a nipple in it's place.

Good info. I will replace it with a straight nipple and report back. Thank you flying scott.