2brl-4brl ..4.3 l?

[gtfireftr]

Has anyone done the 2 brl -4brl conversion on. 4.3?
Not really concerned with great power gains, but just
want her to run great. My 2 brl's seem to load up overnight
and take a while to clear out when first started.
Carbs were rebuilt last year.
Not a fan of the Mercarb 2 brl.
Any advice is greatly appreciated.

 

[gtfireftr]

Noone?

 

[Dieseljeff]

You should be able to get the 2 barrels running fine...maybe running too rich?
On the other hand, 2 to 4 barrel carbs + the intake manifolds should net ~ 20 hp per engine.
Probably not much difference in fuel if you take it easy,

Jeff

 

[PlayDate]

A few questions: 1) are the replacement carbs marine grade and what is their cfm rating? 2) Are you replacing the intake manifold? 3) What do you mean that current carbs are "loading up overnight"?

 

[BillK2632]

I am assuming it only smokes / runs rich on a cold start and after it warms up it is fine? Then it is the choke, otherwise you need to look at the float settings. The Mercarb is simple, I rebuilt mine with no issues, but I did have to re adjust the float and choke to get it running right.

I have found that the choke needs to be adjusted very light on the Mercarb, I have mine adjusted almost as far lean as it will go and make sure the choke unloader is adjusted right - 5/64" I think. Boats aren't usually run in really cold weather, so you just don't need the choke like in a car. I rebuilt my carburetor a couple of years ago and it smoked like a BBQ at start up until I leaned out the choke. The initial adjustment specs set the choke too rich in my opinion.

 

[gtfireftr]

A few questions: 1) are the replacement carbs marine grade and what is their cfm rating? 2) Are you replacing the intake manifold? 3) What do you mean that current carbs are "loading up overnight"?

Currently have professionally rebuilt 2 brl Mercarbs....I believe 350cfm....
I would change intake manifolds, and new Edelbrock 1409 carbs (which are marine specific)....
Upon first start the engines stumble for a bit until they clear out fuel..... I think that dumped in overnight.....

 

[gtfireftr]

I am assuming it only smokes / runs rich on a cold start and after it warms up it is fine? Then it is the choke, otherwise you need to look at the float settings. The Mercarb is simple, I rebuilt mine with no issues, but I did have to re adjust the float and choke to get it running right.

I have found that the choke needs to be adjusted very light on the Mercarb, I have mine adjusted almost as far lean as it will go and make sure the choke unloader is adjusted right - 5/64" I think. Boats aren't usually run in really cold weather, so you just don't need the choke like in a car. I rebuilt my carburetor a couple of years ago and it smoked like a BBQ at start up until I leaned out the choke. The initial adjustment specs set the choke too rich in my opinion.

You are spot on....only when cold....
What do you mean by a "choke unloader"?

 

[BillK2632]

What do you mean by a "choke unloader"?

When you pump the throttle on a cold start it "sets" the choke by closing the butterfly valve, however it should not close completely, the "unloader" is part of the linkage on the side of the carburetor that holds the choke plate open slightly and sets the fast idle cam to keep the idle high. If you remove the flame arrestor and watch the choke when you start the engine, you will see that the choke plate is opened slightly immediately when you start the engine (if it is not, or not opened enough it will run rich as heck) and then starts to open as the engine warms, it should be fully open in about 2-3min. The choke adjustment (round thing on side of the carburetor, adjusts the tension on the choke which controls how quickly the choke opens. I have mine set fully to lean (least amount of choke). Also check the 12v wires going into the choke, this is an electric choke, no power, no choke. If this is your only problem, you should be able to get this adjusted and working properly.

Here is a video of how the mercarb choke works: https://www.youtube.com/watch?v=lrbzyHlZSbM

 

[gtfireftr]

When you pump the throttle on a cold start it "sets" the choke by closing the butterfly valve, however it should not close completely, the "unloader" is part of the linkage on the side of the carburetor that holds the choke plate open slightly and sets the fast idle cam to keep the idle high. If you remove the flame arrestor and watch the choke when you start the engine, you will see that the choke plate is opened slightly immediately when you start the engine (if it is not, or not opened enough it will run rich as heck) and then starts to open as the engine warms, it should be fully open in about 2-3min. The choke adjustment (round thing on side of the carburetor, adjusts the tension on the choke which controls how quickly the choke opens. I have mine set fully to lean (least amount of choke). Also check the 12v wires going into the choke, this is an electric choke, no power, no choke. If this is your only problem, you should be able to get this adjusted and working properly.

Here is a video of how the mercarb choke works: https://www.youtube.com/watch?v=lrbzyHlZSbM

Ok... I am definitely going to check this out.... Thanks