4.3 LX Weber carb bog

[joejffrs]

What a fantastic forum! All of the info I got was from this forum before I attempted to rebuild this carb - part numbers and all. So I rebuilt my 93 Maxum 4.3LX 4 bbl carb with the Edelbrock rebuild kit (#1477). I put in a accelerator pump (#1470) which I found out today is not the marine one part #1471. After disassembling the carb - which was pretty clean after 20 years - I used Chem tool and compressed air to clean all passages. Once on the boat, it started right up, idles perfectly but has a bog when I accelerate quickly. It then goes to WOT after the hesitation. Did I miss an adjustment?
I hate to suspect carbs! The reason I rebuilt it is the boat was running out of fuel after a couple minutes of idling, slowly decelerate and then stall. A few pumps and it would start up again. Installed new fuel filter, replaced fuel lines and found that the check valve that comes from the fuel tank to the filter was sticking. Cleaned it with carb cleaner and it operates perfectly.
Could it be the accelerator pump? Seems to be the same one just different seals is what I read.
Thanks for any help!

 

[Volphin]

Re: 4.3 LX Weber carb bog

What a fantastic forum! All of the info I got was from this forum before I attempted to rebuild this carb - part numbers and all. So I rebuilt my 93 Maxum 4.3LX 4 bbl carb with the Edelbrock rebuild kit (#1477). I put in a accelerator pump (#1470) which I found out today is not the marine one part #1471. After disassembling the carb - which was pretty clean after 20 years - I used Chem tool and compressed air to clean all passages. Once on the boat, it started right up, idles perfectly but has a bog when I accelerate quickly. It then goes to WOT after the hesitation. Did I miss an adjustment?
I hate to suspect carbs! The reason I rebuilt it is the boat was running out of fuel after a couple minutes of idling, slowly decelerate and then stall. A few pumps and it would start up again. Installed new fuel filter, replaced fuel lines and found that the check valve that comes from the fuel tank to the filter was sticking. Cleaned it with carb cleaner and it operates perfectly.
Could it be the accelerator pump? Seems to be the same one just different seals is what I read.
Thanks for any help!

The fuel pump plunger is different material and less apt to corrode. I also think it has a slightly different length. I'd pop in the 1471. It's worth the peace of mind.

Now, as to your problem:
Is the accelerator pump adjusted correctly for maximum throw? Check in the manual for proper hole to use.

Did you install the new check ball? If it's missing that will cause bogging.

Are the floats adjusted correctly? You should have set the drop and the resting points.
If the ball is there and floats are correct, then:

Richen your idle screws by 1/2 turn each counterclockwise (out). Retest.
Still bogging a bit? Advance your timing by a few degrees.

Set it to 12-15 BTDC if you can do so without:
A) detonation (pinging)
B) dieseling on when you turn off the engine.

 

[HT32BSX115]

Re: 4.3 LX Weber carb bog

Howdy,

Welcome Aboard!


If you did not pull the fuel pickup and inspect the screen, you might have a look at it.

While you're at it, remove your gage sender and look inside the tank with a small flashlight for debris in the tank. If you have 'stuff' in the tank, get yourself a LONG piece of 3/4" clear vinyl hose and put a piece of PVC pipe on each end. Also put a plastic ball valve on the end you'll use at the fuel receptacle end so it can be closed when the receptacle is full..

This way your helper can close the valve while switching to an empty one and not spill or lose the siphon. Up in the boat, you can use the siphon to "vacuum" the tank and any water or debris in it. Tip the bow up (if the gage sender hole is at the back of the tank) so any water\debris sloshes to the back.


Of course, If you can simply remove the tank, that will be a little easier than siphoning the fuel.

But if you use a 3/4 clear hose, and it's fairly long so you can get maximum height between the fuel level and the fuel receptacle you're siphoning to, you'll get good suction and fuel flow.

DO NOT start the siphon with your mouth! Just use a small funnel, close the valve end and fill the hose with fuel before placing the other end in the tank.


DO THIS OUTSIDE. NO SMOKING, have a fire extinguisher ready etc........



Also, take a close look at the vent. If you remove the fuel filler cap immediately after it "stalls" and you hear a "sucking" sound (and you're not near the State Capitol:laugh:, ) You could have a blocked (with debris/bugs etc) vent............


Also, have a look at the sticky messages at the top of the forum. There's some other stuff you can look at related to inability to reach MAX RPM etc...


Regards,



Rick

 

[joejffrs]

Re: 4.3 LX Weber carb bog

Thanks for all the good info. I ordered the accelerator pump and it will be here tomorrow. Everything else I did, including the float levels, however, I had to adjust/bend the floats a bunch from what they were originally. I got the specs/measurements from the sheet in the Edelbrock 1477 kit. Anyone have the correct settings for floats? Thanks

 

[Bondo]

Re: 4.3 LX Weber carb bog

Thanks for all the good info. I ordered the accelerator pump and it will be here tomorrow. Everything else I did, including the float levels, however, I had to adjust/bend the floats a bunch from what they were originally. I got the specs/measurements from the sheet in the Edelbrock 1477 kit. Anyone have the correct settings for floats? Thanks

Ayuh,... Welcome Aboard,.... It's All in here,...

 

[joejffrs]

Re: 4.3 LX Weber carb bog

Thanks Bond-o. Just printed it and headed to the garage now. A bunch more details than the sheet in 4 languages!

 

[joejffrs]

Re: 4.3 LX Weber carb bog

Thanks Rick. Definitely have to check the fuel tank before anything else. Nice setup on getting the fuel out!

 

[jrclocks]

Re: 4.3 LX Weber carb bog

The Merc manual for the 4bbl weber discusses acceleration bog and the 3 holes in the accelerator pump lever. It recommends moving the linkage to a hole further away from the pivot to help eliminate bog. This will lean the accelerator pump, so I assume that the bog can be caused by too much fuel.

The nice thing about this is that its an easy adjustment, so its simple to check and see if this is the issue. The correct accel pump might help the issue as well.

Hope this helps,
JR

 

[joejffrs]

Re: 4.3 LX Weber carb bog

Fuel tank was clean along with pick up tube and screen. Fuel pump tested OK. Installed correct accelerator pump on third pin as was originally. Engine still bogged on acceleration, the small ball and weight were there but there was a spring in there too that I removed, doesn't show a spring there on diagram. Saw a dinged up primary jet so I ordered part 1488 to replace jets. Don't see the size jets in the kit that were in my carb (120 and 140). Anyone know what combo rod and jet will work? Anti-siphon valve installed, getting enough fuel. Hope I'm close!

 

[Volphin]

Re: 4.3 LX Weber carb bog

The jets in your carb should be .098 for primaries and secondaries. From Edelbrock on accel pump adjustment: If you encounter any hesitations or stumbles that do not seem to be related to the basic metering or have not responded to changes in the basic metering, move the pump drive link to one of the holes closer to the carburetor body. This will increase the stroke length of the plunger and result in more pump delivery.

Try moving your accel pump stroke first. Take your idle mixture out 1/2 turn each, and advance the timing to 14 or greater BTDC. Reset your idle. That will fix it up.

 

[Volphin]

Re: 4.3 LX Weber carb bog

Oh, and ask me how I know.

 

[Bondo]

Re: 4.3 LX Weber carb bog

Ayuh,.... Back when I 1st put the 4.3l in my barge, it wreaked with fuel when trollin', especially downwind,....

Once I figured out my Merc/ Weber is an Edlebrock 1409, I bought the Street Strip tunin' kit,...
It was a plastic box, Full a jets, springs, 'n needles,...
BaZillions of combinations,...
That's where that linked manual really comes into play,...

I ended up leavin' the jets alone, 'n swappin' needles, 'n springs to lean out my low end idle, 'n still stay fat enough to run Wot,...

Nice lookin' motor,....

 

[joejffrs]

Re: 4.3 LX Weber carb bog

Thanks Volphin. With as dinged up as the jets were I wanted to fix it all while it's apart. Now waiting for parts. Great looking 4.3!