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View Full Version : Anti-siphon needed?

chrisrub
05-03-2009, 05:43 PM
85 V20 with an OMC Sea Drive 1.6 liter. Having a running problem. I isolated the problem down to the main fuel tank. Runs fine on a separate 6 gallon.

I've replaced the fuel lines, filters, primer bulb, fuel pickup and a new anti-siphon fitting. Then I took all the old gas out of the tank that I could and added fresh new gas with some startron.

The 6 gallon doesn't have an anti-siphon fitting on it. Thats the only difference between the two set ups.

Would it be a bad idea to take out the anti-siphon valve on the main tank and just run a straight fitting?
cterrebonne
05-03-2009, 07:53 PM
US coast guard requires boat builders to install an AS vavle or an accesable valve that can be closed comming off the pick up in case of fire/fuel hose leak. i run a straight barb. but if you still want to be able to close off your fuel supply you can install a valve that screws into the fuel pick up. if the straight barb doesnt fix it, you might want to pull your fuel pick up out the tank.
Steplift 72'
05-04-2009, 08:45 AM
US coast guard requires boat builders to install an AS vavle or an accesable valve that can be closed comming off the pick up in case of fire/fuel hose leak. i run a straight barb. but if you still want to be able to close off your fuel supply you can install a valve that screws into the fuel pick up. if the straight barb doesnt fix it, you might want to pull your fuel pick up out the tank.
I've ran into trouble with an anti-siphon valve where the motor would intermittently lose rpm and would shut down if the throttle wasn't pulled back. The motor was vapor locking apparently because the AS valve spring was too stiff. I believe this problem is more common during months where "winter gas" formulation is used by the refiners, especially in spring when the weather begins to warm up a little. That can be really dangerous to the powerhead to lean out at cruise speed.
cterrebonne
05-04-2009, 08:48 AM
I've ran into trouble with an anti-siphon valve where the motor would intermittently lose rpm and would shut down if the throttle wasn't pulled back. The motor was vapor locking apparently because the AS valve spring was too stiff. I believe this problem is more common during months where "winter gas" formulation is used by the refiners, especially in spring when the weather begins to warm up a little. That can be really dangerous to the powerhead to lean out at cruise speed.

thats why i dont run an A/S valve.
Skools Out
05-04-2009, 08:51 AM
i removed it from all mine so far too many issues with them. run a straight barb.
reelapeelin
05-04-2009, 10:09 AM
Never had one on mine...:sleep:
chrisrub
05-04-2009, 04:15 PM
It's coming right off then. Thanks guys.
nymack66
05-04-2009, 04:38 PM
I removed mine also, it was restricting my fuel flow
Steplift 72'
05-07-2009, 03:42 PM
i removed it from all mine so far too many issues with them. run a straight barb.
Agreed. I removed mine also but I tend not to make that recommendation when flammables are involved. UL apparently believes they serve a purpose, but their manufacturing tolerances aren't tight enough. What I did at the same time was support the fuel line where it never dropped below the level of the top of the tank so siphoning shouldn't be an issue. I'm sure there are many boats where that isn't possible.