Mercruiser 140 3.0 Dead spot when coming out of idle

[tu1aher1]

I apologize if this has been asked before but any help anyone could give me will be greatly appreciated.

Last season the boat ran well. I had a new Rochester carb put on it and ran well except at cruise speed. This was due to crud in the tank. Well, during the winter I removed the tank and cleaned it up now it's like a new tank. So I just installed the tank last week and started it up and it will run in idle, a little rough, but as soon as I push the throttle forward, it will die. It doesn't matter if I push it fast or very slow out of idle. If I push it past that first part, the engine will run high speed just fine.

Keep in mind this is a new carb or new rebuilt carb that I installed last year. I don't think I winterized it right though. So I thought maybe I just need some seafoam through the system and clean out the carb, so with five gallons in the tank I put in a whole bottle of sea foam in and ran it a good 20 or 30 min and keep trying each day but it still does the same thing.

I verified that there was no air getting in the line by installing a temporary clear hose right before the carb and there are no air bubbles at all. I am using a electric fuel pump and I am around 4 pounds of fuel pressure to the carb.

I did notice one thing, when in idle and looking down into the carb, I notice that only one of the barrels is dripping a drop of fuel every few moments the other one does not. Is this normal? Do I need to tear apart the carb and clean it? I hope not but I will if I have to.

I did play with the two idle screws but in the end I just closed them and gave them both two and a half turns out and left it there.

Any help would be greatly appreciated.

Thanks.

1984 17' Hammond
Mercruiser 140/ 3.0 sterndrive
Rochester double barrel carb
26 gal fuel tank to Rancor fuel/water separator to electric fuel pump then to fuel pressure gauge to carb

 

[Bondo]

Do I need to tear apart the carb and clean it?

Ayuh,.... That would be My guess,....

Ya installed a new carb, with a bad fuel tank,...
That means the carb passed a load of crap, before ya cleaned out the fuel tank,...

Make sure the carb kit ya buy has the accelerator pump in it,...

 

[tu1aher1]

Thanks for the reply Bondo, Since the carb is so new do you think there's a chance I could take the carb apart and simply clean the parts and accelerator pump part very well and put it back together? I am familiar with rebuilding the Mercruiser carb pretty well. Perhaps if I was extremely carful I could clean out the jets and put it all back together? What do you think?

 

[Bondo]

Ayuh,... The tough part is not rippin' the gaskets, but, Hey,.. Go for it,....

The accelerator pump is what richens it to get it up to speed, hence the stutter comin' off idle,...

 

[tu1aher1]

Thanks I forgot about that part. I'll have to be real careful.

 

[Grub54891]

If you do rip the gasket, When installing the new one, I take a dab of grease or Vaseline, and rub it on the gasket. Wipe it off, and install it. If you have to take it back apart, it usually comes off easily.

 

[tu1aher1]

No Title

Bondo you were spot on. Take a look at the pic. The four brass tubes with the orifices were all clogged up. I was able to take it apart without ripping the gaskets. I cleaned it out and when I put it back together it completely eliminated the dead spot and now it runs like a dream. Thanks for the advice. Thanks a lot grub54891 for the advice. I'll do that next time.

 

[fishrdan]

That's a nasty mess in the bottom of the bowl... Do you have a water separating fuel filter on the engine? I'd add one, $30-50 would probably cover everything needed to install it.

 

[tu1aher1]

Fishrdan, yes I do have a pricy Racor water filter but unfortunately I added it after I found out the problem in my gas tank. I was chasing that problem for a while before I found out about all the junk in my tank. I purchased a new carb then later I added the filter. That's why the junk was able to get into the new carb.

 

[Bondo]

Bondo you were spot on. Take a look at the pic.

Ayuh,... That's enough to be a problem,.......