5.7 EFI Vacuum Line

[SJ Sea Escape]

1997 Mercruiser
5.7 EFI
Engine # 0K190814

Thanks for looking at this - bought an older deck boat (1997 Kayot). Took it out, ran great. Used it in a couple of holiday parades, essentially idling through the harbor. Seemed to run rich. Did a tune up - changed plugs, wires, rotor, distributor, oil, filters and MAP sensor.

Took it out again, would only reach 2,000 RPM WOT.

Known good fuel
Checked plug wires, all good
Checked connections, all good
Checked throttle cables to ensure WOT, good

Finally trailered it to a Merc-authorized mechanic (he let me pay him for an hour or so of diagnostic rather than wait a month to get it in). Nothing showed on scan. He checked fuel pressure - it went to 90 psi.

I've pulled the pressure regulator from the cool fuel system and I am waiting for replacement. The screen between the regulator and cool fuel system is cupped into the cool fuel system (pictured). I didn't want to pry it out, but it's clean on the side facing the regulator.

Confused/concerned, though, because the vacuum hooks into the flame arrestor, not the manifold. Is that correct? It doesn't seem like it would generate much vacuum. The inside of the flame arrestor has a tube with a tab that slides in and out manually (pictured). Is that an adjustment?

Thanks again, Jonathan

 

[alldodge]

Yes, vacuum line goes to inside of flame arrestor (thanks for serial number)

With 90 psi then its the regulator, screen, or line going back to filter. Anywhere from regulator to the filter will increase pressure if the is a restriction.