how to adjust carb on 4.3L mercruiser

[ahunter4063]

I can get the engine to start and idle good. I start to have problems when I push throttle lever forward. When I get to about half throttle the engine will spit, sputter and die, unless you catch it quick enough to pump the lever a couple of times to keep it running. Note: Carb was rebuilt recently and I did take it off, disassemble and cleaned. Carb is a 2 barrel, and I think it is a Mercarb. There is an adjustment screw on the front of carb at the bottom. I appreciate any help as the wife has a boating/camping trip planned for next weekend and all boat mechanics in my area cant look at for another three weeks at the earliest.

 

[alldodge]

Re: how to adjust carb on 4.3L mercruiser

Could use a bit more info please. How was it running before you rebuilt the carb? Was it running as you said before it was rebuilt? What is the year and serial number of the engine?

 

[ahunter4063]

Re: how to adjust carb on 4.3L mercruiser

Engine serial # is 0C765828.
It has been a little over a year since I had it on the water due to other engine problems(starter,flywheel needed to be replaced). I'm not sure that it means anything or not but when it dies it will shoot a large flame out of the carb.

 

[alldodge]

Re: how to adjust carb on 4.3L mercruiser

The serial number matches up to a 3.0L 1987-89 model. Backfiring through the carb usually indicates a timimg issue. Is the timing set to speces? If the carb was working with bare minimum capability it shoould be able to run up to speed if brought up slowley, but the backfire shows cause for other issues. You mentioned replacing the flywheel and starter, what caused that to be needed?

 

[Bondo]

Re: how to adjust carb on 4.3L mercruiser

I can get the engine to start and idle good. I start to have problems when I push throttle lever forward. When I get to about half throttle the engine will spit, sputter and die, unless you catch it quick enough to pump the lever a couple of times to keep it running. Note: Carb was rebuilt recently and I did take it off, disassemble and cleaned. Carb is a 2 barrel, and I think it is a Mercarb. There is an adjustment screw on the front of carb at the bottom. I appreciate any help as the wife has a boating/camping trip planned for next weekend and all boat mechanics in my area cant look at for another three weeks at the earliest.

Ayuh,.... Welcome Aboard,... I'm guessin' the float level is off, 'n it's runnin' outa gas, the lean condition causes the backfire,...

Yer savin' it by pumpin' the throttle, 'n the accelerator pump is keepin' it runnin',...

 

[ahunter4063]

Re: how to adjust carb on 4.3L mercruiser

The teeth on the old starter were wore out pretty bad and the flywheel had several ground up and missing teeth on it. I pulled the motor and replaced these things myself as I had a crane available for me to do so. The motor was also locked up so I had to free it up. I have read a little bit about adjusting the timing but I don't have the timing light to do this. Is that something I could purchase and where can I find the specs for the motor. The motor is a V-6. The number I posted earlier was off of the cover over the carb. I'm going out now to actually verify if the number stamped on engine is different and will repost the correct serial number if what I posted earlier was wrong.

 

[alldodge]

Re: how to adjust carb on 4.3L mercruiser

Bondo has more experience then I so I will yeild to him. Bondo what say you about how to fix his issue?

 

[ahunter4063]

Re: how to adjust carb on 4.3L mercruiser

The number that is stamped on the block is CSZ192247. All dodge, thanks for the info. Bondo, I'll pull the carb back off later tonight or tommorow afternoon. Can you tell me exactly what to look for or do once it is apart. Also do you think I need to invest in a timing light since I did not do that.

 

[alldodge]

Re: how to adjust carb on 4.3L mercruiser

The number embosed on the block doesn't give us what is needed. Bondo thinks its lack of fuel but with the large flame of fuel coming up through the carb I'm thinking timming. You need to figure out if you are getting fuel. If you disconnect the throttle linkage can you move the carb butterfly and see fuel be pushed into the carb? If so the carb may be getting fuel.

Pull off the fuel line going to the carb and put the end in a container and then crank the engine. See if the fuel flow comes out smoothly and see in the container if there is anything in their other than gas.

 

[ahunter4063]

Re: how to adjust carb on 4.3L mercruiser

The carb is getting fuel. One of my thoughts was bad fuel since it had been in the tank for almost a year. I got a can of seafoam for the fuel and retried the engine. It starts good and sounded good while idling. If you go to give it throttle it spits, sputters and dies. I did unhook the fuel line and ran it into a container of good fresh gas(containing no ethanol of course). This did not help any. Still idles great but same spitting, sputtering,backfires and dies. As posted before I did not use a timing light on it and I agree it needs to be done. Do you have any info on how to adjust the timing. Sorry about the serial number. It is a 1990 v-6 I know for sure and there is a place where it has 4.3 LG stamped on motor. Do you know what to look for on the float that bondo is talking about?

 

[bonzoscott]

Re: how to adjust carb on 4.3L mercruiser

You should get a timing light. Maybe you know of one you could borrow. You could possibly time it close by testing on the water/lake, twisting the distributor a little at a time, running, repeating etc. Wouldn't recommend though.

 

[Bondo]

Re: how to adjust carb on 4.3L mercruiser

The carb is getting fuel. One of my thoughts was bad fuel since it had been in the tank for almost a year. I got a can of seafoam for the fuel and retried the engine. It starts good and sounded good while idling. If you go to give it throttle it spits, sputters and dies. I did unhook the fuel line and ran it into a container of good fresh gas(containing no ethanol of course). This did not help any. Still idles great but same spitting, sputtering,backfires and dies. As posted before I did not use a timing light on it and I agree it needs to be done. Do you have any info on how to adjust the timing. Sorry about the serial number. It is a 1990 v-6 I know for sure and there is a place where it has 4.3 LG stamped on motor. Do you know what to look for on the float that bondo is talking about?

Ayuh,.... I've been tryn' to link ya up with the factory manual, with little luck so far,...

The Timing needs to be properly set, but runnin' perfectly a Idle, still tells me it's a Carb issue, when ya throttle it up,...

 

[ahunter4063]

Re: how to adjust carb on 4.3L mercruiser

I'm gonna pull the top part of the carb off this afternoon and inspect/clean again. Wish I knew what to look for though.

 

[alldodge]

Re: how to adjust carb on 4.3L mercruiser

Your looking for any kind of stuff in there that shouldn't be there, dirt, water, etc. If it looks clean then need to check fuel pressure which should be 4 PSI or more. If you have fuel pressure, fuel flow and carb is clean (no jets clogged) then its something else.

 

[ahunter4063]

Re: how to adjust carb on 4.3L mercruiser

UPDATE: working on boat all afternoon. Cleaned carb again and adjusted timing properly! I now have what I believe is a perfectly functioning boat. Now to get it out on the water because it has been way to long. Thanks so much for all the suggestions and help. I would have never figured it out if it wasn't for your help and this forum.

 

[noideawhat]

Re: how to adjust carb on 4.3L mercruiser

What could cause the timing to go out? Just happens over time? Just wondering I'm kinda havin the same type of problem. Sry for jumpin on your post

Cheers