fume tube

[4604me]

I want to change my flame arrester to a larger one. I'm now running a fume tube on my old arrester, do I need it, the motor's not covered, and it seem most boats with a scoop dont have them. if I don't need it can I just plug it off at the fuel pump, or is that a no no. thanks

[SmokinLowriderSS]

It's not really a "fume" tube. It's where the weep hole is on the fuel pump so if your diaphram starts to leak, the liquid gasoline pumps into the carb and not into the bilge. On an uncovered engine, it might be OK to just leave open, but here's what I did when I went to a K&N filter setup on a covered engine.
One of the diffs on a marine carb is a tube on 1 side of the top plate for this very line to hook up to. On my automotive 4150 Holley (orriginal to the boat) there is no tube, but a circular impression in the casting on the left side of the top plate, left of the L/H Primary venturi.
I drilled this out, and permenantly epoxied a piece of 1/4" copper tubing into it (JB Weld). I had already bent the tube into a sorta bent "S" shape so it reached fwd & slightly outboard for the tube, and dumped directly over the split between the venturis. Now, if my fuel pump starts leaking, it pumps into the carb still, and I can run whatever (USCG legal required as I have a hood) air cleaner setup I want.
Sorry, no pix of it to post or send ya, but if you have a holley, it's pretty obvious, and really easy. The hardest part is the 1/4" soft copper (air conditioning) tubing is not usually available in small pieces. I have quite a few feet of extra still here.

[4604me]

thanks for the info smokinlowrider SS, I go out to the garage today to play with the boat and I'm looking at the carb. and low and behold there it is right in front of my face. A vent tube with a plug on it, just where you said it would be, I've seen it there before but it just did't click. thanks again.

[SmokinLowriderSS]

No prob, glad to help. :boxed: