MerCruiser 350 Mag MPI - surging/popping

[Belchy]

Hey folks,

I'm hoping someone will be able to shed some light on my issue. I've got a 2005 Merc Mag 350 MPI. Serial # is 0W312634.

It seems around 3200-3800 RPM the motors RPM starts to surge about 200-300 RPM either way. When I back off the throttle it starts to "pop" (sounds like pop corn popping). I've had a mechanic out on the boat a few times, and it has his confused, as it is not showing any errors on the computer. We changed the wires today, the cap late last year. I haven't changed the plugs yet. Should I?

Checked the fuel pressure today, and it was 39PSI. I was told these engines have about 37-42PSI. Does this sound right?.

I also have changed the fuel water seperator as well, and run high octane fuel.

Is there an inline filter somewhere in the gas line that could be clogged, as this only happens above the 3000 RPM range.

If someone could help me with this it would be greatly appreciated.

Thanks!

Brad

 

[Belchy]

Re: MerCruiser 350 Mag MPI - surging/popping

Any body able to provide some insite on this?

 

[EddiePetty]

Re: MerCruiser 350 Mag MPI - surging/popping

......I've said it before (else where) and I'll say it again: Just 'cause ya' got pressure, don't mean ya' got volume.
Start back-tracking your fuel system looking for restrictions, soft fuel lines (on the suction side), clogged strainers/filter/anti-siphon valve.
Do you have a manual??

 

[Aloysius]

Re: MerCruiser 350 Mag MPI - surging/popping

That doesn't sound like adequate pressure. If it's a CSFI system, it needs 45#'s just for the injectors to open.