** HELP - 2007 5.7L - Running rough...I've tried everything...I think. HELP **

[mmadore21]

Issue:
At about 580 hours (15+ hours ago) she started running "rough" again. I do know about the crappy distributor cap and design. I've had the boat since 190 hours and this felt like the exact same issues I've had 5 times in past 400 hours. A new cap an rotor has fixed it EVERY time. Rough = Worse at mid range RPMs between 2500-3100 RPMs. Feels electrical like skipping, slight popping. Feels like text book dist cap issue....but isn't

Facts:
2007 Ski Nautique (206 - open bow)
5.7L PCM GM Vortec
595 total hours
We are in Maine - we only ski May - Oct
125+ hours on the boat this summer - just saying so you know we use it, and I need it to run right. That's a lot up here for half a summer.
Dist cap replaced about 50 hours ago...AND started May with a new one
Wires: new last season 7/2016 summer (Spark Plug Wire Set, 5.7L EXCALIBUR, PCM # RK120018) - they SHOULD still be good. 230-250 hours on them now
Plugs: new in spring 5/17

This is what I've done:

Feels electrical so...

1. Immediately replaced cap and rotor again (crappy one from Mexico, I was cheaping out) - no luck, still rough
2. Thought maybe a bad/cheap new cap and rotor - replaced next day with a good Sierra ones - no luck, still rough

Note: (125+ hours on the boat this summer - dist cap replaced about 50 hours ago too).


Could it be a jug of bad gas?
(We usually run 91-93 with ethanol..and blue marine Stable pretty regularly - no gas or marina on the lake, 5 gal jugs every time)

1. Ran a can of Sea Foam and bottle of NAPA Mac's dry gas for about 1 hr of use to see if just a bad jug of gas - no luck, still rough
2. Drained tank - 10 gallons out...left about .5 gallon in. Ran a small bottle of K100 dry gas and 5 gal of 93 NoE gas - no luck, still rough
3. Ran 5 more gal of 93 NoE gas - no luck, still rough
4. Replaced the fuel filter $$$ in the Fuel Control Cell - no luck, still rough (Looked used and dark but not terrible. Not good but not terrible)
5. Inspected and cleaned the in line little 'pre-filter' - no luck, still rough (it did have some crap in it but nothing serious)(designed to catch jelly beans and squirrels and there were a few in there, but not terrible)

After all that she was better, but still ran rough.

Could it be fuel pressure? - Borrowed a pressure gauge. Fuel pressure at idle was fine. About 57.5 on the dial. I should have tested at higher RPMs I guess...but looked good.

Could it be a bad coil? I bit the bullet and replaced it $$$ - no luck, still rough (Better, but still rough. We can ski at 32-34mph now BUT forget lower than 31 mph. 3100 RPMs and lower still pops and hesitates a bit. I mean you can feel the hesitations at higher RPMs but the boat stays at speed and its not terrible. But not right either. Again, below 3100 and she starts to feel and sound bad.

After all that she as better, but still not good.

Could it be battery terminals? - Took them off an cleaned them up - no luck, still rough. New battery last summer. She's strong like bul and terminals are clean.

Could it be bad pugs? - I bit the bullet and replaced with AC Delcos $$$ - no luck, still rough (had new ones on from the spring. I do oil, plugs, filters, etc every spring)

Wire$$$ next...why not??? (new last season 7/2016 summer (Spark Plug Wire Set, 5.7L EXCALIBUR, PCM # RK120018) - they SHOULD still be good. 230-250 hours on them now)

The nice guys at Nautique shop 2 hours away say they need to put a lap top on it and I can have the boat back in about 2 weeks. Great guys but 2 weeks not an option right now. Anyone else have a suggestion? Oh, to make matters worse we have a pro (current well know name and top 10 in the world) coming in on Monday for a clinic. Grrrr. We have a spare boat but not ideal.

Lap top diagnostics sounds like the answer...but...

[Quinner]

Try a genuine GM cap and Rotor from Napa

[mmadore21]

Nautique tech put diagnostics on it. Coded for cam position sensor. Replaced that. Also, timing was set to -3.5 for some reason. Tech set it to +6.5. She rips now!!!

[93Euro]

What's your engine temp at? I went thru something very similar this spring. Changed all the same parts you did. Ended up being the thermostat. I thought that my temp gauge was just broken because it never moved. Just was never warmed up and made it run very rich.