Anti-siphon valve removed??

[fishweed]

I have a 1993 Johnson 200hp running off a built in 40 gallon tank. The anti-siphon valve on the tank was removed sometime during this boats life for who knows what reason. A side from the fact that the USCG requires one on this boat, should I install a new valve? I was thinking maybe one of the many owners removed it to fix a fuel restriction problem some time ago.
Just out of curiosity, which way does the fuel tend to siphon when the valve is not present?

Thanks in advance for your input.

 

[WillyBWright]

Re: Anti-siphon valve removed??

Only sterndrives and inboards are "required" to have them. Outboard boats are equipped with them for liability reasons. Many are rigged somewhat haphazardly with little attention paid to how the fuel line is installed. Too many riggers just connect the outboard fuel line and let the thing lay wherever gravity will take it. If it develops a leak from rubbing on some sharp edge below the fuel level, gas could leak into the bilge and BOOM.

The antisyphon valve is a weakly loaded check valve that prevents gas from syphoning out of the tank and into the bilge should such a leak occur. If your hose is installed haphazardly where that could happen, put one in there! If the hose is carefully installed and appropriately anchored so that it cannot be below the gas level, you don't have to. It has to run uphill all the way from the tank and never be below the top of the tank...anyplace...anytime.

The only outboards that should have a problem with antisyphon valves are little ones run at idle speed all the time. One big benefit is that gas in the line shouldn't run back into the tank as the motor sits, making priming the gas a whole lot faster.