Hard start warm, pic of carburetor (leaking?)

165 HP, Inline 6 Mercruiser, Rochester 2GC carburetor:

I thought I solved my warm start difficulties but seems like its happening again. Engine starts up fine when cold. Starting up when warm IMMEDIATELY after shutting of engine is no problem. Let the boat sit for a few minutes and starting is difficult. I end up removing the flame arrestor to let the carburetor air out because I have a feeling its flooded.

So, I let the enging idle up to normal op temp, shut it down, removed the flame arrestor and looked inside. Everything I could see was dry. I let it sit for a about 5 minutes, checked again and noticed the venturi cluster and the screw that holds it down was wet with fuel. Is this an indication the float bowl is leaking. I wiped the fuel off the screw then checked again after 30 minutes and the venturi cluster and screw are still wet, and looking down through the throttle body I can see a mist which I assume is vaporized fuel. It's difficult to tell, but trying to look through into the maifold, it looks wet...but can't say for sure.

The carb has been rebuilt twice since 2002. Once by your truly, and once by a company that specializes in rebuilding carburetors, and the problem of hard starting when warm has always been present.

Is it time for a new carb? Could there be a crack on the body somewhere causing it to leak and flood? Should it be completely dry in there? Or is what I'm seeing in the carb normal after shutdown? I've enclosed a pic to show what I'm seeing.

Re: Hard start warm, pic of carburetor (leaking?)

I had this exact issue, for the last 1.5 seasons. I assumed it was the float as well, but a rebuilt carb didn't do the trick. I had been tossing the idea of a carb/intake upgrade around for a while, so a few weeks ago I bought all new parts and installed them. Wouldn't you know....the same flooding issue happened.

It ended up being the fuel pump. Who would have thought that a failing fuel pump would actually make MORE prsesure than it's designed to. I replaced the fuel pump, and the problem was instantly solved.

Hope this helps-

Re: Hard start warm, pic of carburetor (leaking?)

If it is the fuel pump, wouldn't the pressure only be high while the engine is running? The boat has been sitting for a couple hours now and the parts I pointed out are still wet with fuel. But thanks for the suggestion. I plan on checking the fuel pump pressure as soon as I get the righ tools.

Re: Hard start warm, pic of carburetor (leaking?)

One would think it would only be high when running. However, mine would flood itself shortly after shutting off the engine. If I started it within 30 second or maybe a minute of shutting it off, it would start fine. Any longer than that and it would flood.

Re: Hard start warm, pic of carburetor (leaking?)

Your problem sounds more like a heat soak issue. The over-pressure fuel pump should leak gas from the time you shut it off, until the pressure left in the line drops to 5-6lbs. Repeat the process you performed, but this time keep the carb cool with a wet towel. If that significantly reduces or eliminates it, consider getting a phoenelic spacer to isolate the carb from the hot intake.

Re: Hard start warm, pic of carburetor (leaking?)

But... I have also seen a small piece of debris in the passageways cause this as well.

Re: Hard start warm, pic of carburetor (leaking?)

I agree a piece of debris could cause this, but the carb has been rebuilt twice with new seats and needles so I'm ruling that out. Makes sense too that if the fuel pump pressure is too high, it would keep leaking even with the engine off until the pressure drops to within specs of 5 to 6.5 psi. So I'll check the pressure first before trying the phenolic spacer.

Re: Hard start warm, pic of carburetor (leaking?)

Hooked up a pressure gauge and it's within specs at 5.5 psi. So that rules out the fuel pump, correct? I also noticed within 5 minutes of shutting the engine off, the pressure dropped to 2 psi. So I'm back to the question about the carb leaking as seen in the pic. Is it time for a new carburetor?

Re: Hard start warm, pic of carburetor (leaking?)

Just wanted to bump this up to see if anyone can tell me with the correct fuel pump pressure I found with the pressure test, should the carb be wet as shown at the start of this thread? Is that a "definite" sign I need a new carb?

Re: Hard start warm, pic of carburetor (leaking?)

I wiped the fuel off the screw then checked again after 30 minutes and the venturi cluster and screw are still wet, and looking down through the throttle body I can see a mist which I assume is vaporized fuel.

Click to expand...

Just curious, did you reinstall the flame arrestor for that 30 minutes or was the carb left to open air?

Re: Hard start warm, pic of carburetor (leaking?)

Yes, I reinstalled the flame arrestor after every instance of checking the carb.

Re: Hard start warm, pic of carburetor (leaking?)

from s/m #2.
"carb. floods

needle and seat worn, damaged or dirty
float adj. incorrect
leaky float
carb gaskets leaking (borken or brittle material, loose screws)
cracked carb body
auto choke defective or out of adj. (flooding on hot starting)
excessive fuel pump pressure
clogged flame arrestor"

Re: Hard start warm, pic of carburetor (leaking?)

kaliona, I had a similar problem last season. Here's an excerpt from that discussion.
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#4 August 24th, 2009, 10:21 AM
EddiePetty
Petty Officer 1st Class
Join Date: Aug 2008
Location: Courtland, Virginia
Posts: 266

Re: Mercruiser 470 - Stalling

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Hey Al !!
I have the exact same boat, just a year newer. I also had the same problem last year.
Run the 470 until it warms enough to pull the choke off (on muffs will suffice). Shut her down, remove the flame arrester and verify that the choke is open. Peer into the throat of the carb, blow out any remaining fuel vapor (a single breath will do) and look for LIQUID fuel either puddled around the throttle plate or dripping from the boosters.....either case is a sign of a leaking needle valve, too high a float or excessive fuel pressure (It could also be a loose carb horn).
A carb re-build, with particular attention to float height solved my problems.
As a foot note: I used a NAPA kit (be carefull, there are two sizes of the two barrel kit at NAPA). The replacement needle body was a 1/32" shorter than the original. The only way I ever got the float height correct was to shim the needle body by a 1/32".

FWIW.....Ed in 'ol Virginny
Hope this helps ya'.

Re: Hard start warm, pic of carburetor (leaking?)

kaliona said:

Just wanted to bump this up to see if anyone can tell me with the correct fuel pump pressure I found with the pressure test, should the carb be wet as shown at the start of this thread? Is that a "definite" sign I need a new carb?

Click to expand...

Missed the earlier post. Fuel pressure is fine. Did you try the cold wet towel as I suggested?

Re: Hard start warm, pic of carburetor (leaking?)

Tried the cold towel but still see fuel in the carb. I think I'll give the float adjustment one more look. Maybe get a rebuild kit. I can make it through the summer season with the boat acting up the way it is. It has always "eventually" started after removing the flame arrestor and letting it dry out. It's an annoyance I wish I didn't have to deal with.

Re: Hard start warm, pic of carburetor (leaking?)

A few years ago working on cars and rebuilding those 2bbl, the brand of needle and seat made dramatic differences. Some would never seat and leak. Just because it's new, dosen't make it right. Do a 3rd carb overhaul and be clean!