Mercarb 2BBL on 3.0LX Flooding

[flash3610]

I am fighting with a strange flooding problem with a rebuilt mercarb 2BBL. When cold, the engine starts and behaves itself and accelerates fine and good RPM at WOT. After decelerating and then intentionally shutting down the engine and sitting on the water, it will not start and fuel is dripping onto the throttle plates. I can eventually get it started again and it will run fine until the next time a stop the engine. Here is the list of things that I have done so far:

- Rebuilt and cleaned carb
- New spring-type needle assembly
- Adjust float level (14MM) and float drop (27MM)
- Adjusted accelerator pump rod
- Corrected throttle cable length
- Measured fuel pressure (5psi or so)
- Installed fuel/water separator
- Replaced spark plugs
- Timed engine

No joy. Should I try another new carb? My original OEM carb was model 807534

Frustrated as all get out!!!!!

 

[alldodge]

Re: Mercarb 2BBL on 3.0LX Flooding

Probably need to reset your float level, I'm guessing your float level is either set to high or your float is sinking.

 

[Don S]

Re: Mercarb 2BBL on 3.0LX Flooding

Does the choke work? Sounds like it stays closed all the time.

 

[bonzoscott]

Re: Mercarb 2BBL on 3.0LX Flooding

Your float adjustments should be made without depressing the spring in the needle. Is that the way you adjusted? Spring loaded needle is for shock in a rough bouncing situation, such as ATV or motor bike. Honestly, I didn't know they were in I/Os. Either way, it would stop the flow of fuel early and shouldn't be dripping down the carb bore. Somehow, the bowl is being pressurized. Is it an electric pump?

 

[flash3610]

Re: Mercarb 2BBL on 3.0LX Flooding

Thanks for the responses and suggestions. I will once again pull the thing off and triple check the float setting. I will pay closer attention to the float level measurement related to the depression of the spring in the needle assy. Should I do the float level check with the needle assembly removed?

It is a mechanical carter style fuel pump with the 1/8" spacer gasket installed. The pressure shouldn't vary with a mechanical pump, right? I did measure it with a fuel pressure gauge and while the gauge needle was jittery, it hovered around 5psi.

 

[flash3610]

Re: Mercarb 2BBL on 3.0LX Flooding

Does the choke work? Sounds like it stays closed all the time.

No, the choke has been wide open even when the engine is cold with the warm weather we're having

 

[bonzoscott]

Re: Mercarb 2BBL on 3.0LX Flooding

Thanks for the responses and suggestions. I will once again pull the thing off and triple check the float setting. I will pay closer attention to the float level measurement related to the depression of the spring in the needle assy. Should I do the float level check with the needle assembly removed?

It is a mechanical carter style fuel pump with the 1/8" spacer gasket installed. The pressure shouldn't vary with a mechanical pump, right? I did measure it with a fuel pressure gauge and while the gauge needle was jittery, it hovered around 5psi.

No - adjust float level with needle in.

 

[flash3610]

Re: Mercarb 2BBL on 3.0LX Flooding

Here is what solved my problem and it was thanks to helpful input. The short story is that it was my flame arrestor. It hasn't been cleaned since I bought the boat in 1996 and was very dirty . I noticed that the engine started and ran fine when I had it off but after beeing convinced I had the problem solved and reinstalled the flame arrestor and engine cover that it flooded when I tried to start it. This happened twice during this ordeal and I should have put 2 and 2 together but it wasn't until Don S suspected that my choke must me closed that got me thinking that perhaps the flame arrestor was essentially choking the engine. The choke when fully closed must create enough of a vacuum to open the needle valve since when I tried closing it fully by hand today it killed the engine and caused the same fuel dump into the carburator throat. I cleaned the flame arrestor and took 'er for a test run today and had no problems. Thanks for your help and happy times on the water!