PDA

View Full Version : Popping @ WOT????


87MCProstar
04-13-2010, 01:02 PM
I was able to get boat out of storage over the weekend!!! And with my April vacation this week I took the boat for its first lake trip this morning after just having to charge the battery, luckily it fired right up and ran like a champ, until it was at wide open throttle. There it would feel like it was missing a little and then you'd hear a pop, like a backfire through carb. Once this happened I shut her right down and idled back to ramp. What would make that happen? Nothing was out of the normal other than at wide open. Any insight would be great. thanks

thatsmrmastercraft
04-13-2010, 01:08 PM
The simple answers would be a misfire while under load. Plugs, dist. cap, rotor, points (if you still have them), plug wires, incorrect timing and old gas would all cause this.

JimN
04-13-2010, 01:09 PM
I was able to get boat out of storage over the weekend!!! And with my April vacation this week I took the boat for its first lake trip this morning after just having to charge the battery, luckily it fired right up and ran like a champ, until it was at wide open throttle. There it would feel like it was missing a little and then you'd hear a pop, like a backfire through carb. Once this happened I shut her right down and idled back to ramp. What would make that happen? Nothing was out of the normal other than at wide open. Any insight would be great. thanks

Could be rich- what does the exhaust smell like- strong gas odor? When is the last time you looked at the distributor's centrifugal advance weights and springs? When did you verify the timing last?

87MCProstar
04-13-2010, 01:11 PM
I didn't change plugs, didnt have 20 hours on them, new wires/cap/rotor/points. timing wasn't off when I put away for winter. I'll throw some dry gas in, and see if that helps

87MCProstar
04-13-2010, 01:12 PM
Running rich could be it, there is a strong smell of gas in back seat

east tx skier
04-13-2010, 01:24 PM
Every time I've ever heard a "pop" sound, it has always been because of a loose plug wire. Double check them at the plugs and the distributor.

etduc
04-13-2010, 03:56 PM
I didn't change plugs, didnt have 20 hours on them, new wires/cap/rotor/points. timing wasn't off when I put away for winter. I'll throw some dry gas in, and see if that helps

Corrosion, never sleeps. :rolleyes:

TMCNo1
04-13-2010, 04:00 PM
Also check for a broken plug.

NoMoreBeggin MC
04-13-2010, 05:46 PM
I just had the same popping problem. when you throw the throttle down it almost like backfires through the flame arrestor. I adjusted the timing (just a little) and she's running great now!

87MCProstar
04-13-2010, 07:49 PM
sweet, looks like i have a full day tomorrow!

TRBenj
04-14-2010, 11:36 AM
Was it popping or pinging? Pinging at WOT would indicate too much total timing. You need to check initial and final (which should be all in at 3k rpm). You dont want to see any more than 36 total.

Whats your base timing set to? What grade of gas are you running? Did you stabilize the fuel last fall?

87MCProstar
04-14-2010, 12:11 PM
It was definately popping not pinging, my base timing is 10*, i'm running 89, and I did stabilize last fall.

TRBenj
04-14-2010, 12:23 PM
Double check the final timing (at 3k or so) anyways. Popping could also indicate a crossed plug wire.

454Prostar190
04-14-2010, 12:39 PM
My S and S popped, like you described at WOT, first time out last year. I performed nothing mechanical, adjusted nothing and a fresh tank of fuel solved the problem.

87MCProstar
04-14-2010, 09:02 PM
okay, I'll try to run this tank out and try a fresh tank. all wire connections seemed good. I didn't try to check timing, I didn't have time today

CantRepeat
04-14-2010, 09:21 PM
Double check the final timing (at 3k or so) anyways. Popping could also indicate a crossed plug wire.

If the firing order was off then it would do this at all RPMs.

Jerseydave
04-14-2010, 10:06 PM
a backfire through the carb usually means an intake valve is open on the compression stroke. Check your ignition timing, if its way off your timing chain may have jumped a tooth. Or you could have a sticky intake valve (from winter storage) or worn cam lobe for one of the intake valves.

KHall
04-14-2010, 10:15 PM
I would run out the old fuel. Mine acted funny with the first tank out, new fuel type just doesn't last, stabilized or not.

TRBenj
04-16-2010, 10:11 AM
If the firing order was off then it would do this at all RPMs.
Ive seen V8's idle smoothly and run half way decent at slow to moderate speeds even when theyre only running on 6 cylinders. Ive seen a few start and idle smooth on 4 cylinders. Yes, I could tell something wasnt right- but not everyone is "in tune" to things like this. I agree that bad gas or timing is a more likely culprit, but the firing order is certainly something to double check.

CantRepeat
04-16-2010, 10:22 AM
Ive seen V8's idle smoothly and run half way decent at slow to moderate speeds even when theyre only running on 6 cylinders. Ive seen a few start and idle smooth on 4 cylinders. Yes, I could tell something wasnt right- but not everyone is "in tune" to things like this. I agree that bad gas or timing is a more likely culprit, but the firing order is certainly something to double check.


Dropping a cylinder because of a bad plug or plug wire is totally different then have the firing order wrong. Instead of a situation where something does not fire it's more of firing at the wrong time. With the firing order wrong you have all kinds of things that can happen, backfiring through the exhaust or crab are just a couple of them.

IE 1 8 4 3 6 5 7 2 going to 1 4 3 5 7 2 is completely different then going to 1 7 4 3 6 5 8 2 :D

JimN
04-16-2010, 11:43 AM
Getting back to the plug wires- if they're old and leaky, you could have a cross-fire issue.

CantRepeat
04-16-2010, 11:49 AM
Getting back to the plug wires- if they're old and leaky, you could have a cross-fire issue.


If that were the case, wouldn't happen a lot more then at WOT? It would seem anytime, even at idea this would be an issue. At least bad enough that if you open the engine cover you would at least notice it happening.

87MCProstar
04-18-2010, 04:42 PM
Just seemed like a combination of bad gas and first run out. Took the boat out two days ago and all those symptoms were gone. Thanks for the info, if this happens again I won't freak out.

TRBenj
04-19-2010, 01:02 PM
Dropping a cylinder because of a bad plug or plug wire is totally different then have the firing order wrong. Instead of a situation where something does not fire it's more of firing at the wrong time. With the firing order wrong you have all kinds of things that can happen, backfiring through the exhaust or crab are just a couple of them.

IE 1 8 4 3 6 5 7 2 going to 1 4 3 5 7 2 is completely different then going to 1 7 4 3 6 5 8 2 :D
Im well aware of the differences. I have experience with both, but my comments were in regards to crossed wires. Ive played with several early 70's 302's that I was initially unsure of their firing order... it was around this time that Ford switched the 302 to a 351w FO. The 4,5/7,3 cylinders are the only difference- and either can result in a running engine... but not always on all cylinders.

Tim, glad it was something simple!