Sputtering Carb

[Marlin275]

Stumped by my Holly?
350 Crate / Volvo 270

Had the carb rebuilt 3 months ago.
When the boat starts up it runs fine to 3000 RPM then sputters with slight
droplets of water in the carb.
After about 30 minutes it clears up and works flawlessly no water in fuel/water separator.
I sent it back to the carb rebuilders once but it still does the same thing.
Went on vacation and it did this everyday, once on warm up then ran rest of day with no problem?

Condensation?

Boatyard guy says need new carb?
Wouldn't rebuilt be as good?
How would new make a difference?

[MOP]

Is there a possiblilty that water is dripping from above, maybe a scoop or hatch seam. I have seen that cause the carbs to get wet.

Phil

[Dixie Doug]

Some times if you store the boat inside it can cause condensation.(cool outside,warm inside)Try fuel dry.

[Marlin275]

Is there a possiblilty that water is dripping from above, maybe a scoop or hatch seam. I have seen that cause the carbs to get wet.

Phil

Phil,

No scoop on X18,
hatch does leak down,
but not anywhere near carb?????????

[Rootsy]

OK, what are you calling water and where is it located, etc etc etc. i assume you are running a flame arrester.

youo don't need a new carburetor. just need to figure out what is wrong with yours... or with the engine...

is this half hour of running or half hour of idling?

[Marlin275]

OK, what are you calling water and where is it located, etc etc etc. i assume you are running a flame arrester.

youo don't need a new carburetor. just need to figure out what is wrong with yours... or with the engine...

is this half hour of running or half hour of idling?

Small droplets that I picked up with a Q-tip inside the top of carb.
Causes loud popping sounds when they pass through.
Half hour of idling or lots of throttle work.

[Rootsy]

Small droplets that I picked up with a Q-tip inside the top of carb.
Causes loud popping sounds when they pass through.
Half hour of idling or lots of throttle work.

this is very weird... small droplets of water should not make the motor pop like you describe...

are you sure this is water and not gasoline? can you see where the water is coming from? your fuel pump has a hose that should be running to the carb from it in case the diaphram leaks... that way the gas is poured down the carb instead of in the bilge or crank case... it's a yellowish transulcent hose.

the popping noise concerns me for that is more of a late timing or lean issue... or a leaking intake valve kind of issue... are you getting water in the oil at all? have you pulled the plugs to see if there is water on any one of them? if you have water ingestion for whatever reason it may be coughing back up through the intake and carb depositing the water....

if either end plug on either side of the motor is wet then you most likely have an intake leak...

as a "rough" adjustment your idle needles should be initially 1 1/4 - 1 1/2 turns OUT from lightly seated. your butterflies on the primary side should not be uncovering more than 20 - 30 thou of the transition slot... if so then crack the rear butterlfies (small setscrew in throttle plate beneath secondary vacuum diaphram assy on a vac sec carb).

on another NOTE... you have idle and high speed air bleeds in the carb. if you look at the carb from above... on either side there are very small (.030 inch dia kinda thing) holes.. 2 on either side of the accelerator discharge nozzle... if they get plugged then you'll draw a helluva lot of fuel into the carb due to an amplified signal to the idle circuit... the bleeds decrease the signal and imulsify the fuel with air prior to entry into the throttle plate / venturi's. get a can of carb cleaner and feed her some rpm and keep it steady state.. stick that plastic hose on the can and right on top of that bleed and give her a blast... sometimes tehy can get plugged with oil from the crank case vents and or debri or such...

had this happen on my demon this spring... wouldn't even idle.. it went extremely rich... little carb cleaner and whala all better...

lastly.. where is your float height set? if you remove the site plug from the side of the carb with the boat sitting in the water, running, at idle.. the fuel should JUST trickle out of the hole...

hope this helps a bit

[PaulO]

It is not uncommon to have small droplets of water form as condensation on the choke butterfly or high up in the throat of the carburetor in humid conditions. I have seen it many times at certain stages of warm-up. I don't think this is your popping problem. Probably caused by a temperature differential caused by the differing density/velocity of air as it enters the carb. Popping could be caused by choke not opening fully or as stated prior lean condition or leaky intake valve. Also possible spark cross-over onto wire causing spark to occur in cylinder with open intake valve. Start with the simple stuff first. Check the operation of the choke as the engine warms. Check the cap and wires for degredation and/or signs of spark bleeding.
PaulO