2001 250 ox66 running issue

[Bangstick310]

ok so I have change everything from the fuel tank to the motor, drained the fuel tank went completely fresh, brand new fuel lines, filters, VST filters, fuel water seperator, starts perfect runs up to 4500 rpms perfect not a single hiccup and when I go to try and WOT it gets up to 5000 the slowly backs itself off without movement of the throttle in increments of 100 rpms, don’t know where to start. I did notice the fuel bowl half full even while running. Is this something that is normal or can it be the problem. Thank you

[DennisG01]

That's the normal range for the fuel bowl.

When it backs off throttle, describe that better... like someone turning a switch, or slower?

Put a fuel pressure gauge on the engine and go run the boat again... what does the gauge read before and after the issue happens?

I don't remember the exact procedure off the top of my head, but it's pretty straight forward: Check the low pressure pumps with a vacuum tool. I forget if you also check pressure, but look in (buy one - well worth it) the service manual for the procedure.

These are good things to do before just replacing parts.

[Bangstick310]

That's the normal range for the fuel bowl.

When it backs off throttle, describe that better... like someone turning a switch, or slower?

Put a fuel pressure gauge on the engine and go run the boat again... what does the gauge read before and after the issue happens?

I don't remember the exact procedure off the top of my head, but it's pretty straight forward: Check the low pressure pumps with a vacuum tool. I forget if you also check pressure, but look in (buy one - well worth it) the service manual for the procedure.

These are good things to do before just replacing parts.

ok without me physically throttling back , it does it itself. Kinda feels like a safe mode. I’ll throttle up and try and bring it to 5000 and it don’t wanna do it. It would go 5000 then it Drops slowly in 100 rpm increments to 4300 or 4500 without the throttle moving from when I brought it to 5000. What kind of fuel pressure gauge should I get and what is optimal range of pressure? I don’t have the manual. I have to look to buy one.

[pstephens46]

Try a quick test. Have someone pump the primer ball aggressively when the problem starts around 5000 rpm. That’s a quick way to point towards low pressure fuel pump issues.