Anti-siphon valve...friend or foe?

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Halfhitch

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I had an anti-siphon valve stick closed on a previous boat so I replaced it with a regular barbed fitting. The day it happened I was taking some family members for a look-see cruise out of Olympia, Washington in Puget Sound. After launching the boat and starting the engine while tied to the dock, I left everyone there and went to park the truck. When I came back the engine was off. I asked why they had turned off the engine and they said.. "it just died". It was a 4 year old Yamaha F150 and it never died before that. I tried restarting and no luck. It took me the best part of an hour at the dock to figure it out and get it going. Needless to say the enthusiasm for the trip had waned but we were off. Me smelling like gasoline and the women cold and shivery from standing around. We all know that's not good. I never put that ASV back in and the engine never stumbled again.

Now here I am with a new to me 2004 Grady. My first Grady, and yes, now I see there is "a difference". The boat is in exceptional condition and when checking out the aluminum tank...."lo' and behold"... the enemy!...an ASV. I see that it is constucted of different material. The one that caused me grief was made of aluminum. This one appears to be brass or bronze. I haven't scratched through the patina to see.

I am wondering if the Grady owners have experienced a downside to the ASV installed in their boats. Have you ever had trouble with it? Have you removed it altogether? Have you replaced a bad one with a new one? Whats your opinion of the necessity of haveing one? I would like to hear any views/opinions for or against these little wonders.

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The ASV is DEFINITELY your friend. DO NOT remove it. This is used on ALL boats, not just Grady's. It's sole purpose is to keep your bilge from filling up with fuel if a hose should spring a leak. Bad things can happen, both to you/family and the environment, if the valve is removed. If you want, just remove it and clean it out every few years with Brakleen. I believe it's also a CG requirement - so IF there should ever be an insurance claim centering around fuel leakage and the ASV was removed... good luck getting a payment.
 
I personally know two people who had problems with them (at a bad time).
I have heard many times on other forums to remove them because they are a problem waiting to happen.

I did not have one on my last boat. When I replaced the fuel tank, the tank shop did not put one on, they put on a new straight thru barbed fitting.
I researched it 10 years ago and seem to remember that the requirement was for inboard motors and where the tank is higher than the motor (or the fuel line dips below the tank height).
My line went up to a filter.
I put on a fuel shut off valve instead.That way, if I had to remove the fuel line in an emergency or had a leak in a line, I could shut it off at the tank.

I have not checked my new-to-me Grady tanks for them yet. Tanks were replaced by PO last year.
 
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That's what I have understood is that their function is to prevent fuel from getting into the bilge due to the siphon effect but if the fuel line and engine are above the top of the tank they are not required and really have no use. The thought that they are to prevent drain-back from the engine I believe is in error. The first line of defense for that occurrence would be the fuel line bulb it would seem to me.

I will probably leave the ASV on my tank but carry a straight through barb fitting in my kit, should it ever act up.
 
All boats do not have them. Remove it if you have an outboard.
 
I looked up the CG requirement and, Skunk, you are correct from what you researched years ago. As long as the fuel line stays completely above the tank the ENTIRE time to the engine (whether OB or sterndrive) - no dips, or possible dips - then it is not required. But, you'd have to physically check the fuel line along it's entire path. Simply "removing it because the boat has an OB" would not be good advice. The law has nothing to do with OB or Inboard - it seems entirely dependent only on tank height vs fuel line height.

For what it's worth, I've worked in the marine business for 30 years and I can probably count on one hand the amount of times that a failed AS valve has come up. Sure, it happens, but it is pretty rare. But maybe that's also because the places I have worked at are inland and subsequently get better fuel quality (on-road gas stations) on average? We have also been big on recommending fuel additives and I think it's very reasonable to assume that since the additives help to prevent fuel from gumming up, the additives help keep the AS from clogging up, too. They are VERY simple thing - a spring and ball. If the fuel passing through it is clean, it's nearly impossible for it to fail.
 
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Lol, I have a buddy that had an old Grady and the anti siphon problem was intermittent- drove him crazy, rebuilt carb, changed filters, coils, wires etc. then by the end of his season he found the anti siphon.

I had one with the problem in the past too... but I figured it out by running on aux tank.
 
I’m experiencing a block of some sort, with the aux tank running descent and the main tank not so good ( hard starts, won’t get on plane etc etc. (383 mag bravo Stroker reman.)

I’m going to try and pull the dip tube and check for a clog and I figured change the ASV on both tanks.

Anyone have any recommendations on a brand and size? Thanks
 
ASV's can be cleaned, in most cases.

Have you checked your vent system on the main tank?

How's the fuel quality in the main tank?

What happens if you switch the lines on your fuel selector valve?
 
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DennisG01 said:
ASV's can be cleaned, I mist cases.

Have you checked your vent system on the main tank?

How's the fuel quality in the main tank?

What happens if you switch the lines on your fuel selector valve?
Click to expand...
Haven’t checked the vent system yet. When I filled the tank fuel came out of the vent.

Fuel quality is 50/50.


I haven’t switched the lines on the selector yet.
 
DennisG01 said:
ASV's can be cleaned, I mist cases.

Have you checked your vent system on the main tank?

How's the fuel quality in the main tank?

What happens if you switch the lines on your fuel selector valve?
Click to expand...
What solvent do you use to clean the asv?
 
50/50 - based on that comment, it sounds like that's a possibility. Siphon some out from the bottom of the tank after it's been sitting still for a few hours.

Brakleen is easy.

Still check the vent system - even low spots in the vent line could cause a plug. Opening the fill deck plate vents the tank.
 
DennisG01 said:
50/50 - based on that comment, it sounds like that's a possibility. Siphon some out from the bottom of the tank after it's been sitting still for a few hours.

Brakleen is easy.

Still check the vent system - even low spots in the vent line could cause a plug. Opening the fill deck plate vents the tank.
Click to expand...
I’ll definitely check the vent for sure.
I’m also going to pull the dip tube to check the screen in the pickup.
I have a new asv on Thursday and will try and get it all done on Friday.

I’ll let you know how I make out
 
To check the vent, just open the gas cap, go for a run and see if the problem goes away
 
24.17.11 Fuel distribution systems shall be provided with antisiphon protection by keeping all parts of fuel distribution
and return lines above the level of the tank top from the tank to the carburetor inlet or its equivalent (e.g., throttle body,
port fuel injection, or a location where fuel leakage cannot enter the boat when the boat is in its static floating position); or
if the fuel tank top is located below the level of the carburetor inlet or its equivalent, and the fuel line is
rigid metal or USCG Type A1-15 hose, by installing a manual shutoff valve directly at the fuel tank connection, arranged
to be readily accessible for operation from outside the compartment.

This is from the ABYC H-24 GASOLINE (PETROL) FUEL SYSTEMS which meets or exceeds USCG requirements.

Anti-Syphon valves are installed in every production built boat that is ABYC and NMMA certified. They are not required in all gas powered installations. They are a problem in many Outboard powered boat installations and are not needed in most installations. The requirement is the fuel line must stay above the top of the tank heading to the carburetor of fuel system used by the motor. In outboard applications this is normally achieved if the gas tank is installed below the deck. Having worked on outboards professionally for 30 plus years and troubleshooting many fuel systems one of the biggest failure components of the fuel system is a failed stuck partially open anti syphon valve. Motor starts ok idles ok but fails to operate at higher rpm and load conditions. Basically starving from fuel running lean. I never trusted anti-syphon valve to do what they are intended to. In all the boats that I worked on that were outboard powered, stern drive or inboard powered if the fuel lines were or could be installed to run above the tank to the engines fuel system the anti syphon valve was removed from the tank outlet and a manual fuel valve was installed. The first thing I did when I purchased my 208 Grady was inspect the fuel system. This was from the gas tank outlets Fill, vent and motor feed to onboard fuel filter to the change over from the USCG Type A1-15 hose to the outboard engine manufacturer-supplied hose and primer bulb to engine fuel filter to the diaphragm lift pumps. All clamps and hoses inspected for good condition. The next thing I did was replace the anti-Syphon valve with a marine grade fuel ball valve On/off at the tank outlet. The ASV that was installed in the 208's polymer gas tank was an aluminum 3/8" fitting with a stainless steel ball and spring that is calibrated for engines/motors of 200 hp or less. My 208 is rated for 230 hp and has a 225Hp Yamaha Motor. (1) It did not need an anti syphon valve installed and (2) It was the wrong valve. It should have been a brass ASV. Brass ASV’s calibrated for 200 hp and above. Aluminum ASV calibrated for 200 HP and below.
Brian
 
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