Carb Replacement Questions

[robinsbd]

I'm looking into replacing my carb, and I came across a carb that says it replaces the Mercarb part number 3310-864943A01

This one says it is a 2 barrel for the 1998 and newer 5.7L. From that description, I am assuming this carb won't work on my 1997 5.7L. Has anyone used this on a pre-1998 engine like mine? The only reason I like this part is because you can get it brand new.

My engine is supposed to have the 3310-807312A1. I have not found any new replacements yet for this part. I have seen rebuilds and remans, but nothing brand new. Is there any place that makes a new 807312A1?

On the other hand, is there any real issue just buying a rebuilt unit? After discussing with a friend of mine that works on hot rod cars, he felt that a lot of rebuilds don't do anything with the cam shafts and that over time these wear and create vacuum leaks. I'm not sure how much of an issue this on boats.

Thanks!

 

[NHGuy]

It would not have the fitting for the fuel telltale, so not a good fit. The 97 would normally have a mechanical fuel pump and the 98 would have electric.

Your friend is right when it's a car or truck carburetor. Less so with boats.
Road vehicle throttles are constantly changing so the throttle shafts can wear the carb casting and cause air leaks. Boats do much more steady speed so their carburetors don't seem to wear out as fast where the shafts go through.

 

[robinsbd]

Another related question. I was looking at the Sierra 18-7611-2 that is for sale here on iboats.

• Precision Remanufactured to meet or exceed OEM Specifications
• Re-Calibrated and Re-Engineered to Maximize Fuel Efficiency and Performance
• Flow Tested throughout the Entire Throttle Range
• Fuel Mixture and Idle Settings are Pre-Set to ensure that only Minor Idle and Choke Adjustments are necessary during Installation

They say this carb has the fuel mixture and idle settings pre-set. How much adjusting would I actually need to do on it? Can this be bolted on and used safely as is or am I asking for trouble without doing adjustments? I don't have experience adjusting carbs and my marina's service manager said they don't touch carbs.

 

[NHGuy]

Iboats shows the OE 807312A1 available. But it costs a kings ransom $712! On the other hand you are looking at a perfectly good & guaranteed Sierra rebuilt at $403. There is a rebuilder in California that does them for $295, but how long would they take? Both need very minor adjustments after installation. We can walk you through that.
Also if you live near a rebuilder I'd guess there would be some savings with that. And I like the idea of using a rebuilder, that way you may get a person to guide you. There is always the question of how long it will take too.

But here's the big question, why replace it? Are we certain that it's no good? Can we help you get it going?

 

[robinsbd]

NHGuy,

Thanks for the response. I have another post right now regarding my carb issue here: http://forums.iboats.com/forum/engi...0205215-engine-will-not-idle-after-a-good-run

The last time I had it running, I noticed fuel dripping down to the throttle plates.

I need to run the engine again and maybe I can try some things and post an updated video.

At the moment, I can't run the engine because I'm working on installing a new starboard manifold drain fitting.

 

[Rick Stephens]

After advice from these forums, I went with an Edelbrock 1409 600 CFM copy of the Weber marine carb. So much a copy that it has the Weber casting marks. This was not a difficult carb to calibrate. I changed jets and metering rods on the water to get the last little tune.

 

[harleyman1975]

My advice is find a local rebuilder and have it done. You now have somebody to go to if you need help after you install it. I am sure that the rebuilder will be able to help dial it in. This is best done in the water as opposed to on muffs.

 

[NHGuy]

While you get the cooling system complete get on the carb.

Get some line wrenches for the fuel fittings so you don't round off the flats. Get a clear jar or container and pour the contents of your fuel/water separator in there and let it sit to settle. Inspect & throw away the separator. They cause issues if reused.

Unscrew the fuel line that enters the carburetor and check the strainer for junk.

If either of those places have debris let us know. If not put it back together.

Don't use teflon tape on the fuel fitting, it 's a conical fitting of soft slippery brass.

Make sure the threads are going in straight by holding the fuel line evenly against the carburetor inlet with your dumb hand while you start the fitting into the carburetor with your good hand. If you are right handed start the threads with your right hand, if left handed use that to start the fitting.

If you feel the need to use thread sealer there is the white stuff at every auto parts store. It does not need very much.

Screw in the fitting til it starts to touch the housing. Then IMPORTANT, put a wrench on the carb fixture and snug the fuel fitting to the carb fitting without twisting the carburetor body. Hold the wrench on the carb stationary and turn the wrench on the fitting toward the carb wrench.

Don't go super tight, just snug plus a little push. Brass is soft stuff.

Once you are ready to start you'll want to have some carburetor cleaner spray. It removes crud and it will prime your engine so you won't have to wait for fuel to fill the carb bowl and get out the venturis. If you give it a 1 to 2 second burst before cranking, the engine will start right up, it might stall but it will start again more easily because when it started the fuel pump brought you some gas.

Let us know about how it runs, and about the fuel drips.

 

[NHGuy]

The Edelbrock would be nice but it requires a different intake. I think the OP isn't at that point in his wallet or his technical abilities...yet

 

[robinsbd]

Hey guys,
I've been away from the boat for a bit.
I'm back on it now. I replaced my drain fittings on both my exhaust manifolds.

Now I'm back on troubleshooting the carb.

I removed the fuel line no problem using a 5/8 line wrench.

I'm having an issue getting the fuel filter nut to loosen. It looks like there is paint on it that may be holding it. I am afraid to pull too hard on my wrench for fear I damage the carb body. You guys have any ideas?

Here's what I'm working with:

 

[robinsbd]

 

[Bondo]

I'm having an issue getting the fuel filter nut to loosen. It looks like there is paint on it that may be holding it. I am afraid to pull too hard on my wrench for fear I damage the carb body. You guys have any ideas?

Ayuh,.... Turn Harder,.... Lefty loosey,...

 

[NHGuy]

Yup. hold the carb down on some wood and push down on the end of the wrench. It will take some force. Or bolt it back on the engine long enough to loosen that inlet & filter fitting.

 

[robinsbd]

My carb is still on the engine. I got the inlet nut off without any issue. I used my breaker bar and It didn't take much to get it off.

Here is a pic of my carb fuel filter:

 

[robinsbd]

The fuel inlet looks pretty clean though:

 

[NHGuy]

Gross. clean or replace that filter, put on a new separator and give it a shot!

 

[hemi rt]

Don't even try to clean that filter, just replace it and get an extra one as your replacement may get plugged seeing as how much junk is in the original one.

 

[Jcris]

+1 on hemt rt
just replace and recheck after some use
definitely do the seperator

 

[robinsbd]

Ok guys, I replaced the carb fuel filter and the water separator. Since it was due, I performed a full tune up (plugs, wires, cap, rotor, sensor wheel).

The engine starts right up. I run it around 2K RPM to keep it running and get it warmed up. After the choke opens up, it wants to stall if I bring throttle back to idle.

Take a look at my video. Watch the part where I have the camera over the carb. You can see the fuel flowing. Does that look normal for the RPM?

https://youtu.be/hApmVEczFRM

 

[robinsbd]

Here's a video of the carb when the engine shuts down. I see vapor and dripping:

https://youtu.be/1qnVMnVJpp0