Fuel suppliers are replacing tolulene and other good additives with ethanol,it gives you no extra tolerance to detonation because the extra octane it adds is taken away from the rest of the mix. What it does do is LEAN out your actual mixture as it has less energy and btu's. If most the local gas your going to run has ethanol in it then you should definately tune with it so your mixture is safe,Smitty

The O2 tuning was mostly a bust this weekend. We did get the timing set and tested the AFR at idle. We changed the idle air bleeds from 51 to 49. That richened the AFR at idle to about 14.5...hard to be very accurate at idle with big cams as the gauge fluctuates a lot.
Now the water test. We couldn't get on plane as we think we may have an issue with one of the new Crane HI-6 ignitions (winter project). It could be an installation error but we didn't find any issues. From 1000-4000 RPM at the dock, everything including the advance curves was just as expected. The throttle response was crisp and everything seemed right. The idle in and out of gear was sweet....no stalling. We went out in the river and never got on plane. The Stb engine backfired and quit at 2000-2500 RPM coming on plane under load...WTF! Tried twice but something was wrong....idled back to the trailer.
Carb and fuel systems seem fine. Checked and rechecked the Crane wiring Port vs. Starboard and didn't see any issues. The fuel pressure was 6.5-7 lbs and the HI-6 boxes worked fine up to 4000 RPM at the dock. As this issue only shows under load,
is it likely the coil? There wasn't enough time to switch components engine to engine.
Today, I found and ordered a new Crane 6000-6462 marine box and LX-92 coil. We will be ready to parts swap in June as needed. Does anybody have any suggestions of where to look for additional ghost on my June trip?

Sounds lean, my boat won't get on plane at those A/F ratios.

14.5 is just at idle at the dock. The AFR is where it is set at13.5-13.6 in the mid-range. It isn't possible that the starboard carb has an issue, but it doesn'ts seem likely. Thanks for the thought, we will swap carbs for one of the test.

Did you happen to check a plug

Backfired out the intake or the exhaust?

Didn't check a plug...backfired on intake (carb)

Here is the current plan pre-launch:
1. Check the Stb plugs (If typical move on)
2. Swap carbs
3. Install new Stb coil
4. Water test
Results:
If no back fire, it was the Stb coil. If the Port backfires it is a lean carb (assumes FP is good). If the Stb still backfires, it is likely the ignition box.
4. Change out the Stb ignition box and retest.

Stb still backfires?....make offers

I got the boat on the water yesterday and did a little tuning. I found the boat liked 13.5 at idle all the way up to 3400 RPM. I did not test WOT yet. I will post updates on my other post Roller Cam Upgrade.

Intake backfire = lean most often. Be careful. Check float level for shore.