Backfire through Carb

[FreeBeeTony]

Splashed the Vortec today.

I started it yesterday and let it run for a while in the drive way..........seemed fine. Replaced the fuel filter/ water seperator and started again and let in run for a while longer.

Put it in the water today. Stared right up, while warming up it stalled and was able to start it right up again.

After it warmed up we started out........when I tried to get up on plane it backfired through the carb.......each time I tried to accelerate. I remember this happening last year and it went away after I changed the fuel filter again.

Well I did the same, changed the filter and it stopped backfiring but, at low RPM's (in a no wake zone) the engine seems to surge. But not enough to really notice it on the tach.........maybe about a 100 RPM surge. Can water in the fuel cause this? I even added an additive to the fuel.......http://www.westmarine.com/webapp/wc.../fuel additive/All_2/mode+matchallpartial/0/0

What could be causing the RPM surging?

 

[f_inscreenname]

Re: Backfire through Carb

Could be timing, water in gas or a sticking valve.

 

[FreeBeeTony]

Re: Backfire through Carb

Whats the best additive to take care of possible water in the gas?
I suspect water due to the Ethanol issue...........

 

[Rob454]

Re: Backfire through Carb

Timing or if you have a distributor you may have a plug wire out of order. My 5 liter ford did that. It idled fine but as soon as I tried to give it any power it would backfire and qwouldnt get past 20 MPH then it would stall etc. the mechanic that id it had some of the plug wires backwards and the timeing at abtou 30*. I ended up fixing it myself with the help of a buddy. That was when after paying 3200$ for the so called pro to do it I decided to do my own work and havent looked back since.
Rob

 

[FreeBeeTony]

Re: Backfire through Carb

Plug wires are ok........timing is fine also.

Can make 4400RPM at WOT..........the only problem now is the low RPM surging.

 

[Haut Medoc]

Re: Backfire through Carb

Carb. or fuel delivery.....
Backfire thru carb is lean mixture or bad valve......
I know you have gone through this engine.....
I think carb......
Leak down test ....
Fuel pressure test.....
Carb........​

 

[FreeBeeTony]

Re: Backfire through Carb

Backfiring is gone.............now just surging.

 

[gwaidman]

Re: Backfire through Carb

Methyl Hydrate (gasline antifreeze) will take care of any water you may have in the system. Even if you have drained the tank, there could be a little water left in the carb float bowls that could be attibuted to the surging you are experiencing. Just my 2 cents.

 

[Limited-Time]

Re: Backfire through Carb

Fuel delivery, or passably a vacuum leak.

 

[FreeBeeTony]

Re: Backfire through Carb

I added 5 cans of dry gas today.......hope this does the trick.

Not too nice out........will have to wait for another for a test run.

 

[Bt Doctur]

Re: Backfire through Carb

If you have to add that much, pull the sender plate and remove any water.
additives in the wrong combination can turn gas into jelly.has happened in boats and aircraft fuel systems.

 

[FreeBeeTony]

Re: Backfire through Carb

Each can treated 10 gals..........i probably have about 90 gals of fuel.

 

[Bondo]

Re: Backfire through Carb

Hey Tony,.......

If that doesn't Help,....... Have a Read in Here,..... It gets into Driveability Issues.....

I found Surging at the end of page 7,......
Mine is got a mid-range lean skip, or stutter.........
I gotta fatten it up abit,..... I'm going to try the heavier Springs 1st.....

 

[FreeBeeTony]

Re: Backfire through Carb

Thanks bondo..........might need to change the rods.

 

[FreeBeeTony]

Re: Backfire through Carb

Which step would you go to bondo in my case..............??

I would think step #21 on page 14 of the link of the manual you provided.

This would put me more towards a rich mode in a high vacum state, which is where I am at low throttle.

Do you agree?

 

[wca_tim]

Re: Backfire through Carb

if surging at even throttle, need more / richer for high vac / cruise mode,if more pronounced when accellerating, need more / richer in power mode... makes sense that your set-up would need to be richened up a little across the board... glad it's running well overall for you...

have been playing with jets / metering rods for the past several days...

 

[Coors]

Re: Backfire through Carb

If fuel is good, backfire is lean condition.
does it backfire when secondaries open, or before?

 

[ziggy]

Re: Backfire through Carb

can't remember all yer issues. but i'm starting to wonder. is the issue following the boat? just wondering. any similarities in issues?

 

[FreeBeeTony]

Re: Backfire through Carb

This thread was from last year........new engine now..........seems like I have a fuel/water problem at the beginning of each season!