Engine backfire when secondaries open Timing not advancing past 12( 5.7 Marine Power

[AS19-1]

Looking for some help. I have a 1975 Formula 233 center console. Engine is a 2001 Marine Power 5.7 with Holley 4 barrel. I will give you a quick rundown of the problem.
Fuel tank leaked and water entered tank. New tank installed. Rebuilt carb due to water intrusion. After rebuilding carb engine ran super rich and would not idle. Rebuilt two more times same thing ended up carb body was warped at metering block union. Problem solved. Ran the boat and all was fine cruising at 3200 rpm my normal cruise rpm. At the end of the day when I tried to open it up increasing throttle from 3200 she climbed to about 3550 normally and then I could tell the secondaries opened and at 3700 she backfired and bogged but pulled back to 3200 and ran fine (secondaries closed). I understand this could be a lean condition but floats are set properly. Does air fuel mixture screws on primary side affect seconday side of carb. Screws are currently set a litle more than 3/4 of a turn out but not quite a full turn. Other variables I am thinking of I changed cap and rotor and set timing at 8 btdc ( timing wrong ?), I did notice spark was more orange than blue when I tested spark with spark tester ( could this have anything to do with it). This work was done at the same time as carb. Any ideas thanks

Edit. I readjusted idle mixture screws to one turn out this seemed optimal but can not test till boat is in the water. Do mixture screws affect secondary operation or only idle circuit. Thanks

Edit 2. I should have mentioned the backfire seemed to be through the exhaust

Edit 3. Checked timing today I had only set initial timing before. Timing does not advance past 12. I guess I need a new distributor.

 

[Bigdave196]

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

Ehhh......Its a Holley, get rid of it for an Edelbrok. Much easier to tune and maintain.
I would look at the jets that are in it but I am not overly familliar with Holleys.

 

[AS19-1]

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

I was almost to that point until I checked the faces of the carb and saw they were warped. Filed them down with a large flat file.

 

[AS19-1]

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

Just readjusted idle screws they were a little lean went from 3/4 to 1 and a hair. Do the mixture screws affect secondary operation I thought they only affect idle circuit.

 

[Bondo]

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

Other variables I am thinking of

Ayuh,... Have ya rechecked the filters for lost Water,..??

I don't do Holleys, so I can't help ya there, but it's No Doubt goin' Lean...

 

[LAC_STS]

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

What IGN system do you have?

My brand new 5.7 with Edelbrock 1409 carb was doing the EXACT same thing as yours except mine was right at 3K RPMs.

Everyone who looked atthe engine/boat thought it was fuel related. I cleaned water from the fuel tank, tried a different carb, fuel pump tests, etc.

Problem ended up being the resistor wire that went to the coil on my points dist.


Like the one member here whos sig says "on sterndrives when everything points to fuel check IGN".

Happened to be true in my case.

 

[AS19-1]

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

New filter was installed with new fuel tank. Ignition is Electronic Delco style. Thanks

 

[ziggy]

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

while i ain't the pro. imho.

, I did notice spark was more orange than blue when I tested spark with spark tester ( could this have anything to do with it)

that ain't right. and best i understand, generally, fix electric before fuel.... best i can help..

 

[Joshua Nichols]

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

Edit. I readjusted idle mixture screws to one turn out this seemed optimal but can not test till boat is in the water. Do mixture screws affect secondary operation or only idle circuit. Thanks

I can't believe no one has answered this for you... Those screws make no difference for the secondary side..

You sure you got all the funky out of it? Bet ya missed something.. Water intrusion in a carb causes all kinds of funkys to grow...

Why did you have to adjust the timing?

 

[AS19-1]

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

I didn't think the screws had any affect on secondaries but wanted to make sure. I set timing after new distributor cap and rotor was installed mostly because it still was running bad after third carb rebuild ( then I read about Holleys warping which fixed my problem) I really don't think I missed anything cleaning the carb as I took it apart and reassembled so many times Blew all air passages with compressed air everytime. I should have mentioned the backfire seemed to be out the exhaust. Thanks.

 

[Joshua Nichols]

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

Have you checked the timing again since now you have the carb running smooth on idle?? I would check to see if the carb is dumping fuel when the secondaries open... Sounds like it isn't to me

 

[AS19-1]

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

Re: Engine backfire when secondaries open ( 5.7 Marine Power )

Does anyone know what the total timing should be on a 2001 Marine Power 5.7 Vortec. My timing wont advance past 12 degrees