anti siphon valve or not

[MBAKER]

I have read many posts about the ASV causing issues of fuel starvation and wonder if I should just change this to a brass nipple?

I have noticed on line there are 2 different ones noted sometimes, one for 200HP and less and one for 200HP and up. The one I have is aluminum which seems like it is for th e200HP and under, but yet it was factory installed on a 225HP mercruiser?

If I remove it are there issues with fuel siphoning back out of the filter into the tank causing startup issues?

If I read the USCG regs correct it says you need to run a anti-siphon valve or ensure the fuel line never drops below the level of the tank. On my sterndrive setup there is a short piece of fuel line that runs from top of the tank, gets tied down at basically the top level of the tank then continues to the engine. It woudl seem like I woudl not be required to have the ASV in this case?

It seems like this could cause quite a restriction as it seems like with the pump running it would pull fuel through and suck the ball with it partially closing off fuel flow to the engine under high flow conditions. I recently removed it while installing new hoses to make sure it was free and clean but now started 2nd guessing if it would be smarter to remove it and prevent a starvation issue.

 

[HT32BSX115]

Howdy,

It's only there to prevent siphoning fuel out of the tank in the event of a leak in the fuel supply line.

If your fuel line never goes below the fuel level, it's not required. An anti-siphon check valve for "200hp" would work fine for 225hp.....

If you have one in the tank, I would keep it. Also, make sure your fuel pick-up screen is clean and clear of debris and the tank is clean.


Regards,

Rick

 

[MBAKER]

What makes me question the HP rating is because last year we swapped out the 225HP 5.0liter, for a 300HP 5.7 liter. It ran fine and never had any issues, but I never knew there was a difference in the valve ratings.

 

[Maclin]

Safety items like an ASV are not so much for normal running as they are there for EXTREME events, like the boat is now upside down on land or dock due to some catastrophe. Many safety items like an ASV are to keep an already catastrophic event from escalating.

 

[Bondo]

I have read many posts about the ASV causing issues of fuel starvation and wonder if I should just change this to a brass nipple?

I have noticed on line there are 2 different ones noted sometimes, one for 200HP and less and one for 200HP and up. The one I have is aluminum which seems like it is for th e200HP and under, but yet it was factory installed on a 225HP mercruiser?

If I remove it are there issues with fuel siphoning back out of the filter into the tank causing startup issues?

If I read the USCG regs correct it says you need to run a anti-siphon valve or ensure the fuel line never drops below the level of the tank. On my sterndrive setup there is a short piece of fuel line that runs from top of the tank, gets tied down at basically the top level of the tank then continues to the engine. It woudl seem like I woudl not be required to have the ASV in this case?

It seems like this could cause quite a restriction as it seems like with the pump running it would pull fuel through and suck the ball with it partially closing off fuel flow to the engine under high flow conditions. I recently removed it while installing new hoses to make sure it was free and clean but now started 2nd guessing if it would be smarter to remove it and prevent a starvation issue.

Ayuh,..... In a boat, at most boats normal Attitude, whether sittin', or runnin',...
Usually puts most of the Motor, below the fuel tank's Top,...
A leakin' fuel line can empty the tank, at the dock,...
That's why ya do a Sniff Test, before ya light her up for the day,....

Fuel pumps run 'bout 5 psi on a carbed motor, it only takes a pound of pull to open the valve,...
I took mine out along time ago,... after givin' it some thought, I put 'em back in, after I fixed the Crud in the tank issue,....

 

[MBAKER]

I was more concerned with the check valve shutting off or restricting fuel flow under normal WOT conditions. I guess as long as it keeps operating fine its nothing to worry about. I found the valve I have on Moeller website and it doesnt have any mention of HP so I am assuming that its a non-issue with their product anyway. Maybe some others are made differently.

If it ever starts acting up its easy enough to pull the valve and check it or replace with an open barb for testing.

 

[Silvertip]

It's been awhile since I read the regulations for ASV installation but I believe it is required on any fuel tank installed below deck. Yes - fuel can't siphon if the line is always above the fuel level in the tank. But -- bow high getting on and off plane changes the fuel level vs engine attitude thus making the chance of siphoning very possible if there is a line leak or rupture. The ball cannot get out of the ASV since it is installed from the tank side of the ASV, not the nipple side. If you are worried about ASV failure, take a spare one with you. They are not budget busters.