#1
IP: 108.88.37.1
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Scavenger tube loose
Hello!
I've recently purchased a Catalina 27 with an A4 and am attempting to isolate the source of a gasoline odor. While poking around I noticed there appears to be some fluid on the scavenger tube fitting, and I am starting to think this is a source. It may also just be Permatex but the odor says gas. While reaching in there (it's a tough reach) I found the scavenge tube elbow fitting on the carb is not tight. Given where it is, I'm not actually sure it can be tighetned with the carb on. So the questions are: Should it be tight? If so, is it possible to tighten with the carb attached? Also, it appears that the elbow must be parallel to the engine which may account for it having not being tight. Not sure how to address that. At this point I'm having trouble even getting in a position to work on it, so up front advice would be appreciated before I contort myself into the lower reaches of the port locker. Also, fwiw I realize there shouldn't really be much fuel getting picked up by the tube and wouldn't be surprised if I've over used the choke and caused more gas than usual to be getting in there. The engine was somewhat difficult to start when I bought the boat but new plugs, gapped correctly last week has it running smooth and starting with a lot less choke. |
#2
IP: 73.213.34.83
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The A4 uses an updraft carb, and this design is inheritly hard to start. A cold A4 should require full choke and 2-3 tries to start if properly tuned. If your A4 starts without full choke or on the first try, it is probably tuned too rich.
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@(^.^)@ Ed 1977 Pearson P-323 "Dolce Vita" with rebuilt Atomic-4 |
#3
IP: 65.110.214.40
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Handy tidbit -- I was wondering since mine almost doesn't like the choke at all. Crank it over on the first try and slap the choke closed as soon as its at idle is my experience. Guess I should read up on carb adjustments.... I'm sure there's a guide around here somewhere.
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yKnot 28' Newport C&C @ PWM |
#4
IP: 108.88.37.1
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Quote:
I'm really more concerned about the scavenge tube, whether I can get to it and tighten while the carb is attached, or even whether its worth being worried about. Last edited by Stiva; 09-05-2019 at 08:53 PM. |
#5
IP: 97.93.70.7
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Safety
The scavenge tube is a SAFETY devise!!! It takes the raw fuel that drips down the updraft carb and routes it to the manifold. This way the fuel does not accumulate and drip out of the carb~boom.
The tube is just a piece of 1/8 copper tubing usually with compression fittings on both ends. The nuts are 3/8 as I remember and should be snug so they don't leak fuel or air. The extra air is especially bothersome for the carb at low speeds. Dave Neptune |
#6
IP: 207.118.20.35
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important stuff
This is a common source of gasoline odor. If you can smell it without putting your nose on the carb air intake, you have a problem. If you can reach in there far enough to know that it's loose, you can reach it to tighten it. A 4 + 1/2 " long, 3/8" open end wrench should do it. That's the only thing I use that wrench for. The previous owner was seriously remiss in not doing that. If the elbow is not pointing forward, turn it so that it is. If you have to remove the carb, do it. You don't want that to drip into the bilge. Then try to get any gas out of the bilge.
On the subject of using choke to start, you should need full choke to start if engine is cold. After running for a few seconds, the choke can open. With mine, once the engine is warmed up it doesn't need a choke to start. I may have it tuned a little rich, but I like to be able to start quickly by just turning the key and pushing the button. I do a lot of 'motor for bit, sail for a bit', and repeat, because I navigate around small islands in a light wind area. |
The Following User Says Thank You to capnward For This Useful Post: | ||
Stiva (09-06-2019) |
#7
IP: 100.36.65.17
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Quote:
The stiffness of the copper tube can make it difficult to align and start the threads grabbing. I've had success by undoing the manifold end and threading the carb end first. The manifold end is much more accessible and I can then get it aligned and threaded.
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@(^.^)@ Ed 1977 Pearson P-323 "Dolce Vita" with rebuilt Atomic-4 |
#8
IP: 207.118.20.35
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I have found that making sure the tube is straight as it nears the fitting helps with getting the threads started. Get it started with your fingers. If you can't do that, don't put the wrench on it.
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#9
IP: 108.88.37.1
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Quote:
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#10
IP: 32.211.28.40
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Just to muddy the waters...
Most of the scavenge tubes I've seen use flare fittings. The nut is slipped onto the tube and then the end of the tube is enlarged with a special tool to make a small cone. This female cone fits over a male cone on the fitting then the nut tightens it all up. No reason a compression fitting can't be used, but that requires a compression ring (I wouldn't use plastic), a different nut, and a different fitting. |
#11
IP: 108.88.37.1
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I was able to get one more full turn on the carb side elbow of the scavenger tube. It seems to be ok now, but should i be concerned about the flare fitting. A!so, would the scavenger tube ordinarily be installed dry or with some kind of sealer goop?
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#12
IP: 24.152.132.140
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Pipe threads take sealant, flares do not.
__________________
Neil 1977 Catalina 30 San Pedro, California prior boats 1987 Westsail 32, 1970 Catalina 22 Had my hands in a few others |
The Following User Says Thank You to ndutton For This Useful Post: | ||
Stiva (09-15-2019) |
#13
IP: 32.211.28.40
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The male half of the flare is machine made and should be good. The female flare in the tube is made on site by the local mechanic using whatever tool he has - and with whatever skill he has.
So, you might need a little permatex (the brown stuff) - I'd put it on the male flare, keeping it out of the hole. |
The Following User Says Thank You to Al Schober For This Useful Post: | ||
Stiva (09-15-2019) |
#14
IP: 64.62.192.42
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The first time that I addressed it, (out of sight, out of mind) I found that the scavenger tube fitting was quite loose. Tightening it up didn’t make any obvious difference. Since it’s a vacuum fitting, rather than a pressure fitting, it ought to be self-sealing to some extent.
Earlier this summer, I took the carb off for cleaning and darn if that fitting wasn’t loose again! But I have had a vacuum gauge installed for a couple of summers now and it had been reading normal vacuum. Which reinforces my opinion. Still, maybe a little permatex would help the nut stay in place. BTW, I’ve hardly used the engine this summer, but it has been starting with no choke. However, I changed three variables: Cleaned the carb, installed adjustable main jet, and installed electronic ignition. Guess I’ll have time for adjustments now that the rains are coming in. |
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