backfire at startup to plane

This one is boggling me and I have not figured it out. Could be old gas, crap gas, or ?
92 Nautique PCM 351 (not the HO)

Through the entire RPM range, runs like a champ... no backfires at all. But from neutral to when you "hit it" or "drop the hammer" I get a backfire in the engine, if I pull back she picks up to speed to fine to full throttle.. no surges, nothing.. just when you first hit it.

I seem to think it is not timing because it has the electronic ingintion system. I'm leaning towards the holley carb... is it too lean or too rich? Seems like if you drop it into foward, throttle to full to a quick pick up, it's either flooding itself out or not enough fuel and it backfires. (forgot which one causes a backfire.

Here is what has been done:
new plugs
new fuel/water filter
oil changed


The only thing I usually do, I have not done yet, is through some carb cleaner down the carb while at the dock and run it through.. just to make sure it's clean....   but I have a feeling it be something else that needs adjusting.

Any tips?

Thanks much!

Actually, it is the ProTec system. Sorry, forgot about that.    I have heard in older Holley's that if it backfires once, the power valve is probably blown or broken.

I'll check the fuel flow down the throttle body tonight if I have time.

Is this replacement procedure for a power valve?

http://www.advanceautoparts.com/english/youcan/html/pht/pht20011001cb.html

If a plug wire is crossed, it would probably backfire through the entire RPM range correct? Not just out of the hole.   And if the coil pack is cracked, would it miss or not come to full power all the way through the RPM to Wide open throttle?

Thanks for your help.. Appreciate it!

Ok, I will check the firing ordering to make sure no wires are crossed.   I did have this problem in my 84' with a wire crossed, but it would backfire right from starting it. So what you are saying is the DIS corrects what it can from the misfire, but the backfires "slip" by when under load.   

thanks!   I still have to check the amount fuel dumping down the carb to ensure that is correct. Flash light was out of juice last night.


tc

Thanks for your help....

One more note.... When I first pulled it out of the garage this season, I took it out on the water for a leasurely cruise. I noticed at about 3k rpm she would not be hitting on all cyclinders and start surging ever so slightly... you could feel it "hit" every now and then. So I increased the speed, then it started to backfire repeatly, probably because it was getting too much fuel I assume, I would pull back to 3k or below to recover.
This is when I replaced all the plugs, fuel filter, changed the oil, etc.    Then this posting.... the high end was fine, no backfires. Just under load or out of the hole.

So maybe you are right... the packs are giving out and just a matter of time before it completely does not run?

If it is the packs, do you recommend buying a new coil pack for this, replace it with something else?

you will want to pull the two plug wires from one coil back at a time, you are looking for the mis to be gone not that it's down on power or idles a little rough which it will, you don't have to run it very long at all a couple of minutes on each pack until you find which one it is. After you do the first one connect them pback and let it idle or take it for a spin before you do the next one, to clean up the plugs that where not firing, disconnect it at the pack and not the plug and wrap a piece of tape on one wire so you know which side it was on.

What you discriped on your one more note sounds like a fuel pump issue and not ignition issue. So while you have the line off to replace the power vlave throw a fuel pressure gauge on it and double check that the pressure is where it should be 5 psi.