Mercarb Marine Carburetor Rebuild

The Mercarb marine carburetor is a 2 barrel carburetor that looks much like the Rochester 2 Jet, with some differences being the single idle mixture screw on the Mercarb, 2 Jet has 2. Jets are a different size, power jet is different, power piston is different. Most parts are not interchangeable with the 2 Jet.

Some Mercarbs have 2 main pieces (top & body), whiles others are in 3 pieces (top, body & throttle body).

Some models will have a clear return tube running from the fuel pump to the top of the carburetor. This allows fuel from a ruptured fuel pump to bleed into the carburetor instead of the bilge (fire hazard). The Mercarb itself is designed for any fuel flooding to re-enter the carburetor instead of the bilge.

The Mercarb is generally painted black, which prevents corrosion to the outside of the carburetor especially when used in salt water.

This carburetor does not use an air cleaner, or spark arrestor gasket.

An electric choke is standard.

These carburetors are no longer manufactured new, so when you need one, you will need to  find a rebuilt unit, rebuild it yourself, or send it to a reputable carburetor shop and have your carburetor rebuilt. The Mercarb is one of the easier carburetor to rebuild, but when you run into a problem experience would be a plus.

 

Mercarb Identification

Finding the carburetor number.
Mercarb Carburetor
Purchase one of our famous Mercarb ethanol ready rebuild kits. At this time our carburetor kit fits all Mercarb carburetors, but if you need to know the carburetor number look near the fuel inlet fitting. You may have to scrape some of the black paint off to see the number. In this case the number looks like this: 1389-9564. Generally the 9564 is enough to identify the carburetor.

Mercarb Rebuild

Take plenty of photos as you take your Mercarb apart. You may need to refer to them when putting your carburetor back together.

Watch our Mercarb rebuild videos.

Part 1 – Dis Assembly

Part 2 – Assembly

Take the carburetor apart, then inspect the parts for damage, or excessive corrosion. White residue at the bottom of the float bowl, which is probably dried up ethanol gas isn’t such a big deal and should clean up nicely.

Look for particles of black rubber. That would be the ethanol eating the inside of your fuel hose. Replace all fuel hoses when this happens.

Since marine engines tend to sit for long periods of time, the gas may have turned and varnished up the inside of the carburetor along with the gas tank. A strong smell of varnish will be present when this happens.

If the carburetor is corroded in the bottom of the bowl, then the carburetor should be discarded. Any corrosion would indicate that one or more of the small passages have corrosion which you will most likely not be able to remove.

Soak in a carburetor cleaner dip purchased from your favorite parts store. Follow the directions on the can. For example one product suggests 20 minutes of soaking. Soaking too long will discolor your carburetor, so be sure to follow directions.

Rinse in hot water, removing all traces of chemicals. Many chemicals react with ethanol gas.

Blow out all passages. As you go along determine where the passages leads, then feel the air going through the passage to be sure it isn’t clogged. Pay special attention to the small holes in the venturi. They can easily get plugged.

Mercarb Carburetor

 

Paint the outside of the carburetor black if needed.

Dirt is the biggest cause of carburetor problems, so be sure to replace all fuel filters. Many good carburetor rebuilds go bad because of dirt in the gas tank.

More technical help –
float adjustment
choke
troubleshooting

 



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