How do I safely remove anti-siphon and intake line?

[TXGlastron]

Once again, I feel stupid. I’m certain I should replace my anti siphon valve. It’s original on this boat I bought. I can’t figure out how to access it.

The gas line into the fuel/water separator is obvious. Tracing back from this filter, the line goes from the engine bay forward into the subfloor area. I don’t see any access panels to get to that area. Is there something under the carpet I’m missing?

I have gone from boating amateur numbskull to just amateur over the last few years. But maybe I’m back to numbskull based on whatever the answer is to this.

Thank you

 

[Lou C]

There has to be access to the fuel tank connections and fuel gauge wiring. Sometimes it’s a round cover screwed into the deck, about 5-6” in diameter. My boat has a rectangular panel that can be removed…the anti siphon valve is screwed onto the fuel pick up tube. The fuel line from the pump/filter connects to it….

 

[TXGlastron]

I finally found it and I feel stupid. For anyone that has this question in the future, it is directly in front of the engine, underneath the floor boards. They are easily removed once you reveal the screws that hold down the cover.

 

[Lou C]

It will always be right where the fuel hose from the pump hooks up to the fuel pick up tube. Excuse the dirty fuel tank my boat is 38 years old and the tank is original. On this boat the whole fuel tank compartment hatch just comes up. Be careful with this valve, it is either brass or aluminum screwed into the aluminum fuel pick up tube. Use a 6 pt socket and hold the square top of the pick up tube steady with an adjustable wrench.
I had to get into mine because I was having a performance problem all of last year. Finally narrowed it down by running the boat on a separate outboard tank with fresh fuel. At the same time, I had to check the original anti siphon and pick up tube just to make sure they were OK. Old, but still working, but I replaced with new because I was in there. Lucky for me it all came apart. The anti siphon I know was last changed in 2004, and the pick up tube I bet was original. The metal ball in the valve can stick from corrosion or debris, and on the pick up tubes, some have a screen on the end that is in the tank, these can clog. Mine were fine, I actually tested them with a vacuum gauge, so I could have just re-used them.
My performance problem was simply fuel had gone bad, never had that before that's why I wasn't expecting it.

 

[TXGlastron]

It will always be right where the fuel hose from the pump hooks up to the fuel pick up tube. Excuse the dirty fuel tank my boat is 38 years old and the tank is original. On this boat the whole fuel tank compartment hatch just comes up. Be careful with this valve, it is either brass or aluminum screwed into the aluminum fuel pick up tube. Use a 6 pt socket and hold the square top of the pick up tube steady with an adjustable wrench.
I had to get into mine because I was having a performance problem all of last year. Finally narrowed it down by running the boat on a separate outboard tank with fresh fuel. At the same time, I had to check the original anti siphon and pick up tube just to make sure they were OK. Old, but still working, but I replaced with new because I was in there. Lucky for me it all came apart. The anti siphon I know was last changed in 2004, and the pick up tube I bet was original. The metal ball in the valve can stick from corrosion or debris, and on the pick up tubes, some have a screen on the end that is in the tank, these can clog. Mine were fine, I actually tested them with a vacuum gauge, so I could have just re-used them.
My performance problem was simply fuel had gone bad, never had that before that's why I wasn't expecting it.
View attachment 415892View attachment 415893

Lou, your post is actually extremely helpful to me! I got the anti-siphon valve off like you. But I wasn't able to get the square head part of it to turn. You are saying I should be able to safely break this free with a 6-pt or box wrench, correct? I have not checked the fuel line and pickup in the tank yet. I would love to do that and make sure all is well on that end.

 

[TXGlastron]

I have circled the part I’m wondering about. I have unscrewed without issue the brass fitting. However, the square aluminum looking block seems stuck. I’m afraid to wrench on it too hard and ruin things. Can you offer advice on how I should break this free? I feel like I really need to look at the fuel pickup line and make certain it is all well, with a clean filter on the end. I’ve been reading this could be my issue as well since I have ethanol fuel. I have winterized the fuel with Seafoam Marine each year.

 

[TXGlastron]

Hi all. I have been able to remove the fuel line clamp, pull the old fuel line off, and even unscrew the anti-siphon valve. But this square head is my nemesis right now. I want to get it off and check my intake line and filter for clogging. How do I safely remove this? Is it just muscle, or is there a thread seal on this as well? This part is new to me. Thank you.

 

[bajaman123]

Terrible picture...
So are you saying you have removed the hose and hose barb and now are just trying to get the 90 degree fitting (the "square head") off? Typically these are brass, and will have some sort of thread sealer on them. Liberal application of Break Free, PB Blaster, Kroil, etc is indicated. Then find an open end wrench that fits the square tightly. After letting the penetrating oil work, rock the fitting back and forth with the wrench...should free up pretty easily.

 

[TXGlastron]

Agreed, terrible picture. But you are correct on your assumption. I have removed the fuel line from the barbed anti-siphon. The square head is what is left right now. I didn’t want to just start cranking on it and break something. After I break it free, is it best to purchase a new one? I.e. are these crush threads on the brass? Really appreciate any hints before I start muscling it and ruin the tank.

 

[alldodge]

The antisiphone valves are cheap, and just replace it
Normally made of aluminum so next to no chance of sparks with tools on the hex head.

 

[TXGlastron]

Here is the non-zoomed in version of the picture.

 

[TXGlastron]

The antisiphone valves are cheap, and just replace it
Normally made of aluminum so next to no chance of sparks with tools on the hex head.

Perfect, thank you! I’m perfectly capable of dumb choices. I don’t mind asking before leaping now.

 

[TXGlastron]

Terrible picture...
So are you saying you have removed the hose and hose barb and now are just trying to get the 90 degree fitting (the "square head") off? Typically these are brass, and will have some sort of thread sealer on them. Liberal application of Break Free, PB Blaster, Kroil, etc is indicated. Then find an open end wrench that fits the square tightly. After letting the penetrating oil work, rock the fitting back and forth with the wrench...should free up pretty easily.

Perfect, thank you. I’ve proven myself to be fully capable of poor decisions. I’m now much more cautious as I learn about boat maintenance.

 

[Lou C]

You want to put a thin wrench on that hex fitting that’s on top of the tank to hold it steady when removing the pick up tube. I was able to get mine out & it was in a 38 year old aluminum tank. Go easy on it, take your time..IIRC they are NPT threads.

 

[Lou C]

This can be a tough job, due to corrosion and even overtightening in the initial installation. I would make sure I ruled out other causes before trying to get the fuel pick up tube out....Mine did come out but not right away, I had to gently move it back and forth after soaking in penetrating oil for a few days. The threads in the tank and on the fitting are NPT threads. After removing both the anti-siphon valve and fuel pick up tube, I realized that I assumed those were causing my "apparent" fuel starvation problem but upon inspection, they were both fine! It was 30 gallons of E10 fuel that went bad, even though stabilized and was less than a year old (maybe 7/8 months). I replaced the old parts with new anyway. Neither pick up tube had a screen on the end. I ran the boat on a separate outboard fuel tank with fresh fuel and it ran great. I assumed that the cause was the anti siphon valve and pick up tube, but inspection revealed that was not the cause! Leaving the gas as the culprit. First time that ever happened in 23 years with the same boat.


testing the old anti siphon valve and pick up tube. anti siphon opened as it is supposed to and the assembly held vacuum as well. So never assume anything lol.

 

[Bt Doctur]

when/if you manage to remove it ,remove the pickup tube from the fitting.It just unscrews the same way. look inside the tube and you may see a SS stent inside the tube, It simply pull out

 

[Lou C]

I searched around on other boating websites as well (esp The Hull Truth) and the consensus is to get rid of that screen. My original pick-up tube and the one I replaced it with didn't have screens. The only drawback to this (as long as you have a proper water separating fuel filter) is that your anti siphon valve could get clogged by debris due to having no screen. But typically, those are easier to replace than the pick-up tube.
BTW, all anti siphon valves are not created equal, one style is for engines under 200 hp the other is for those over 200 hp according to Moeller. The problems you can have with them are clogging and also the cheap ones can rust up and stick. The OEM OMC Evinrude/Johnson ones I have used are of good quality.

 

[Scott Danforth]

Being a plastic tank, make sure you have a backup wrench on the hex insert if you try unscrewing the pickup tube

 

[Lou C]

Yep look for a thin hex wrench for that. You don't want to strip that out in the plastic tank.

 

[TXGlastron]

As an update, I finally got back to the boat again. The hex shaped part actually unscrewed very easy, and appears to be doing nothing. The Square head still needs to be unscrewed from the tank. I have not applied pressure to it yet, hoping to hear advice from this forum before I go an He-Man it off and ruin my tank. Any last thoughts? Anti-siphon unscrewed easily and I have that for replacement. I will definitely check that I am getting the right size for my Mercruiser 5.7L.

Thank you!