Remanufactured Carb Purchase

[wewefirex2x]

I purchased a remanufactured carb at ebasicpower.com. The carb came in the mail today. The carb that is on the boat right now is a mercarb 2 barrel with a single idle mixture screw. My concern is that the one I got today has two idle mixture screws. Everything else looks the same. I called the company and they say it's the same carb. If it is the same carb why does it have two screws up front. The guy on the phone says (Why would anybody wont a single screw carb on a 2 barrel). Because that is all I know from fooling with it the last two seasons!!!
My assumption is that I got a Rochester carb and everything is fine. Any input would be appreciated.

 

[achris]

Re: Remanufactured Carb Purchase

You are quite correct (and it sounds like the guy on the phone doesn't know his carb from his elbow) the Mercarb has only one mixture screw. The carb you received is a Rochester and they have 2 mixture screws. As long as it is a proper marine carb then you are ok to use it. Merc used both during the manufacture of those engines.

Chris...........

 

[wewefirex2x]

Re: Remanufactured Carb Purchase

Yes, it is a marine carb.

 

[Caveman Charlie]

Re: Remanufactured Carb Purchase

Why would anybody want a single screw on a two barrel carb?
Just asking because I don't know

 

[Don S]

Re: Remanufactured Carb Purchase

wewe, I may be wrong here, but I think that the stud spacing for the carb mounting studs are different on the Rochester as compared to your Mercarb.
At least check it out before you get to far along.

 

[Gary H NC]

Re: Remanufactured Carb Purchase

Usually Ebasic has great customer service.I have called them several times.
Like Don said though,make sure the base plate mounts the same.
Its most likely a Rochester 2GC carb.It should work just fine if it bolts up.
I think you start with the mixture screws 2 1/2 turns out.That was the starting point on my last 4.3 with that carb.

 

[rodbolt]

Re: Remanufactured Carb Purchase

like DonS said.
check the carb mounting bolt pattern.
the R2GC was made with a large and small pattern, and about 6 venturi cluster combinations and about 5 throttle link combinations.
the reason for the single screw is the mercarb is just that. it was designed by merc and built for merc by rochester.
by design the R2 was marine compliant as the bowl vent had no choice but to vent down the venturies in event of a carb flooding problem.
the automotive versions did not have a provision for fuel pump diaphram rupture venting.
myself, I would have reinstalled what came off, especially on a 2.5 or 3.0.
so why would ya want a 2bbl with 1 idle air fuel mixture screw? same reason GM put 4 holes in the large base 2bbl and then only used 2 bolts to hold it to the intake.
it worked for better than 20 years and saved 2 bolts on every GM car with a large base R2 carb.

 

[achris]

Re: Remanufactured Carb Purchase

Why would anybody want a single screw on a two barrel carb?
Just asking because I don't know

With a 'normal' carb you have a mixture screw for each barrel (or pair of barrel with a 4bbl), usually for an engine with a dual plane intake, ie V8. That's because the casting has a channel for fuel to each barrel with the mixture screw right by the throttle plate of each barrel. The Mercarb has a single fuel channel to the mixture screw, which controls the amount of fuel for a given volume of air, which then divides and goes to each barrel. So the mixture for both barrel, at idle, is controlled by the one mixture screw. Works better that way on 4 cylinder engines.

Hope that is the answer to your question CC

Chris.........

Chris............

 

[Caveman Charlie]

Re: Remanufactured Carb Purchase

With a 'normal' carb you have a mixture screw for each barrel (or pair of barrel with a 4bbl), usually for an engine with a dual plane intake, ie V8. That's because the casting has a channel for fuel to each barrel with the mixture screw right by the throttle plate of each barrel. The Mercarb has a single fuel channel to the mixture screw, which controls the amount of fuel for a given volume of air, which then divides and goes to each barrel. So the mixture for both barrel, at idle, is controlled by the one mixture screw. Works better that way on 4 cylinder engines.

Hope that is the answer to your question CC

Chris.........

Chris............

OK thanks.