Carb Gasket

[Jimmy]

Finished rebuilding fuel pump and carb.
Benefits noticed include being able to adjust carb so lowest throttle position will allow me to creep forward, instead of always sliding into neutral. Also, when I removed the fuel pump I thought I had good action, as it was, but with the new springs, wow! Stiff priming lever, and it delivers 4.75 psi on gage. Very happy with it all.

One question- the gasket supplied to seal upper/lower section has a bit of overhang, and is weeping/soaked in fuel. Just leave it, or best to trim off excessive? I am quite certain I have a good seal between the two pieces, and what I am seeing externally is from a "wicking" effect.

Admittedly I may be hyper sensitive to this now, but I would prefer to error on the side of caution.

Cheers
Jimmy

[roadnsky]

Jimmy-
In my experience (IME) that dark area is normal. (See pic)
The pic is a rebuild after 2 years. If you look closely, you'll see the "darker" area on the excess gasket.
I'm not sure why it shows as a darker area.
Note that the "inside" area is lighter in color.

[JOHN COOKSON]

One question- the gasket supplied to seal upper/lower section has a bit of overhang, and is weeping/soaked in fuel. Just leave it, or best to trim off excessive? I am quite certain I have a good seal between the two pieces, and what I am seeing externally is from a "wicking" effect.
Admittedly I may be hyper sensitive to this now, but I would prefer to error on the side of caution.
Jimmy

Did you get the gasket from Moyer? Unless the gasket is made from the correct material it will wick fuel as you observed.
The only way to tell for sure is to take the two halves apart and see if there is a seal all around like in Jerry's picture.
IMO you are not being hyper sensitive. Don't blow the boat up.

TRUE GRIT

[Jimmy]

Gasket was included in rebuild kit from MM. Will return tomorrow to check and snap photo

Worth noting that the MM manual is one of the best written collection of instructions I've ever used. Most valuable tool on board!

Cheers
Jimmy

[capnward]

4.75 on the gauge seems more than usual or necessary. I doubt you would get that reading when running, only when priming with the pump lever. This may be forcing fuel past the gasket, with or without an overhang. Even so, this is a serious situation. A gasket should not wick fuel. If the seal is indeed good, it will not leak, even at 4.75 psi. If this persists, try seeing if you can tighten any of the bolts around the gasket. If they are all tight,you may have an irregularity in the surfaces of the carb.

[hanleyclifford]

4.75 on the gauge seems more than usual or necessary. I doubt you would get that reading when running, only when priming with the pump lever. This may be forcing fuel past the gasket, with or without an overhang. Even so, this is a serious situation. A gasket should not wick fuel. If the seal is indeed good, it will not leak, even at 4.75 psi. If this persists, try seeing if you can tighten any of the bolts around the gasket. If they are all tight,you may have an irregularity in the surfaces of the carb.

I agree. A less than perfect mating between the two halves of the carb body coupled with a float set too high could mean trouble. Does your carb have 4 or five machine screws holding the two haves together?

[Al Schober]

That gasket shouldn't wick, even with the overhang.
First thought is that something is hanging up and not letting the two halves come together. Perhaps the venture tube isn't fully seated? I'd try putting it together without the gasket to make sure everything comes metal to metal.
I've seen gaskets wick. We had oil wicking with Navy specified gasket material - 1/8" thick neoprene with canvas reinforcement. Oil was following the threads in the canvas. Navy wouldn't believe us - tied up our lab for a month proving what we knew.

[Jimmy]

OK- mea culpa.....
I had to remove the fuel strainer bowel to access the second/rear bolt on the pump. When I put it back together, didn't realize the rubber seal slipped out. Subsequently couldn't get engine to fire up. I primed repetitively, but no fuel flow ( yea- massive air leak will do that). After diagnosing the issue( and retrieving/installing the lost seal from the bowels of the boat), the carb/ fuel system primed quickly
Some observations..........

Carb has 4 screws to mate the 2 halves
I traditionally over tighten- snapping and striping bolts as I go thru life. Aware of the warnings about soft alloys involved, I didn't this time, however confident I tightened enough.
Float was exactly parallel with mating surface, when held upside down.
Initial prime pressure = 7psi
During running/tuning = 4.75 psi
After shutdown, pressure stayed above 4 psi for at least 30 min.Wasnt taking exact notice of reading, but thought that is was great that the system was staying pressurized for so long......

Is it possible at 7 psi (even temporarily)I have "overloaded" the gasket?

Thoughts?

Fume detector w/ blower relay has been ordered. Hopefully delivered tomorrow

Cheers
Jimmy

[hanleyclifford]

If your needle and seat are holding 4 psi for 30 minutes after shutdown, they are at the head of the class. When the fuel chambers of the carb are full and the needle and set have stopped the inflow of fuel, the gasket should not be exposed to fuel at all. Does your leak/wicking persist after shutdown or does it occur only when the engine is running?

[Al Schober]

To clarify hanley's post, the gasket will be exposed to fuel as the boat rocks and plunges through the waves but the pressure stops at the float valve. The float bowl, gasket, and the carb internals are all basically at atmospheric pressure. With the engine running, there's airflow through the venturi which changes things (and moves the fuel), but that's all low pressure stuff. I saw a document somewhere (Moyer Manual??) that described flows and pressures in the carb at wide open throttle. Kinda went over my head. In my book, it the carb don't work, clean it out (done it a lot lately).

[hanleyclifford]

To clarify hanley's post, the gasket will be exposed to fuel as the boat rocks and plunges through the waves but the pressure stops at the float valve. The float bowl, gasket, and the carb internals are all basically at atmospheric pressure. With the engine running, there's airflow through the venturi which changes things (and moves the fuel), but that's all low pressure stuff. I saw a document somewhere (Moyer Manual??) that described flows and pressures in the carb at wide open throttle. Kinda went over my head. In my book, it the carb don't work, clean it out (done it a lot lately).

Thanks for that Al. Yes, the gasket will get wet with the "rocking" but should not be under pressure. I wonder if that chamber is venting correctly?

[hanleyclifford]

http://www.moyermarine.com/forums/showthread.php?t=242 This is a great reference.

[Jimmy]

Hanley/Al - thanks for the link.
As I have only run the the engine Sat/Sun, I can't say with certainty that the problem is persistent. Proof will come with tomorrow's inspection.
With the info you have added, I will check for a gap at the front of carb.
I'll post a picture of my findings. Extra eyes can't hurt!

Cheers
Jimmy

[Dave Neptune]

Hanley, the carb has an internal vent that feed to the throat chamber under/behind the venturi. I doubt it could get plugged.

I have "sealed" the ends of more than a few 4-screw carbs by running a bead of "hi temp orange or red" silicone around the end of the carb AFTER TESTING!!!! DO NOT USE THE PERMATEX SILICONE WHEN ASSEMBLING!! After the carb has been confirmed good remove and apply the bead on the outside. The one on my carb stays sealed and has for 4 years now others longer.

Worry more about sealing the emulsion well in the center first with a distorted "top half". They can be "flat honed" to reseal if you are careful. Done so many times out here for friends.

Dave Neptune

[Jimmy]

OK- installed new water/fuel separator, than ran engine.
- before starting, checked gasket and gap. Gasket appeared to dry out, but still double checked front all 4 screws. Got a third of a turn. Attached picture is a 0.002 feeler gauge inserted. I am border line forcing it at this point.

Second pic is of fuel pressure gauge, with engine shut of for more than 15 min past.

Third pic is where gasket had become some what saturated, after engine ran 15 min. Not sure if you can make out the detail, but when I compress the external flange of gasket with fingernail, a slight sheen appears

PO had a little something added, that I cleaned up prior to resembling. It came clean using carb cleaner and a rag.

At this point, I am prepared to remove carb, redo with a little sealant, and go again.
Can I reuse the soaked gasket? Dry it out?
Agree?