I have a Yamaha 90hp 2 stroke outboard on my skiff and a 22 gal tank in the hull. The fuel exit and level sender are in the front of the tank. I have a hosebarb coming out of the tank with the checkball in it. Next in line is the fuel seperator and then the the fuel bulb. After 12 feet of hose is the connection to the engine.
My question is, Do I need the barbed fitting with the checkball in it(anti-siphon?)? Can this restrict gas flow enough to starve the engine if ran at WOT for 3-5 minutes? Thanks
I may be wrong, but I believe a manual shut off valve is legal for a replacement of an anti siphon valve, I’ve seen a number of outboard powered Sea Rays over the years with an on off valve rather than an anti siphon valve, don’t know if its just for outboards or not
an anti siphon valve can and will cause fuel restriction issues
im pretty sure spareparts is corect, but i also belive the anti siphon valve, if you read the boat builder regs from the coast guard, is only required if you have an ignition source(engine, generator, etc) and or the fuel line drops below the tank, allowing the possibility for a cut fuel line to siphon fuel from tank and fill bilge, then when engine starts (below deck) the boat explodes. this isnt an issue with most outboards,
I went round and round on this when I was working on my fuel system, and from what I could interpret from the Coast Guard regs, for most outboard powered boats it’s not required, and they definitely cause problems.
Turns out when I pulled the barb on my tank it didn’t even have a check valve in it. I’m pretty sure based on the condition of the boat when I got it nobody had done much of anything to it so I have to assume it was built without a check valve (in 2006.) Not a guarantee I guess, but the builder didn’t use one and I didn’t feel the need to add one.
from what i remember, there is no req’t for a shut off valve either, but probably a good idea. keep in mind it doesn’t really protect your bilge from the possibility of a cut line siphoning gas unless it’s right at the tank outlet.
I’m not a mechanic or a lawyer though, so use my input at your own risk!
Each fuel line from the fuel tank to the fuel inlet connection on the carburetor must:
(a) Be above the level of the tank top; or
(b) Have an anti-siphon device or an electrically operated fuel stop valve:
(1) At the tank withdrawal fitting; or
(2) Installed so the line from the fuel tank is above the top of the tank; or
(c) Provided that the fuel tank top is below the level of the carburetor inlet, be metallic fuel lines meeting the construction requirements of Sec. 183.538 or “USCG Type A1” hose, with one or two manual shutoff valves installed as follows:
(1) Directly at the fuel tank connection arranged to be readily accessible for operation from outside the compartment, and
(2) If the length of fuel line from the tank outlet to the engine inlet is greater than 12 feet, a manual shutoff valve shall be installed at the fuel inlet connection to the engine.
“Anti-siphon protection” is a term applied to the means of preventing the siphon action of permitting fuel to continue to flow out of the fuel tank in the event there is a break or rupture in a fuel distribution line, or if a fitting in the fuel line loosens, creating a leak.
“Anti-siphon protection” may be accomplished by one or more of the following methods:
(a) Keep all parts of the fuel line from the fuel tank to the fuel line connection at the carburetor above the level of the top of the fuel tank. The tank top level is determined with the boat in its "static floating position." Practically, the fuel pump and fuel filter(s) must also be above the tank top.
(b) Install an anti-siphon device at the tank withdrawal fitting. The fuel distribution line may then run below the level o
well I pulled it and replaced with a hose barb without the check ball. I also moved my primer bulb with the arrow pointing up(and at the engine) so the checkball in it actually functioned properly. Boat ran like a scalded ape and didnt starve the engine at top speed for several minutes. Thanks for the help.
