maybe its a pickup issue in the tank, collapsing fuel line to the filter head ?? can you switch this engine to the other tank, my dad had a Caddy with a 500 in it and it would do the same thing, turned out to be debris surrounding the sock on the pickup in the tank........I know most boat pickups don't have this sock

Yup, or a sticking anti-siphon valve.

I have removed a few...the damn aluminum housings used by many anti-siphon valve companies + water/ethanol/etc presents some issues...not too mention aluminum tanks that corrode from this and guess what is the first (if no sock) item this passes thru.

Have also dealt with a few cracked pick-up tubes. Fuel level just above crack...all works fine...fuel level get's just below it...it stalls/dies.

This is why BUP always tells people to try running from a separate fuel tank for testing purposes. Also fuel psi just after mechanical pump. If your fuel psi set-up shos vac also, placing this just before mechanical pump can show if there is too much restriction before pump.

so if filled the tank full and it stopped it could very likely be a cracked tube that is something to test for sure. i can also swap hoses coming off the pickups and going to the engines to see if it changes sides if it does then i know its in the tank. if it doesnt then i would try replacing the hoses on that side as it would be cheap thing to do to anyway.

is there anti siphon valve on the pickups?

if none of thst works i wanted to try swapping ecm side to side and map sensors after that if problem doesnt move try a pressure regulator on the fuel rail. beyond that i will need to get a computer on it and th a t might not tell me anything either. they want 120. an hr the min they step on boat and the way i see it bare minimum 3 hrs testing.

Another thing I was thinking about are there any engine sensors that directly make the ecm shut down the fuel pump. Fact is it's a fuel pressure issue without question pressure starts diving after 3500 rpm needle on fuel pressure gauge bounces up and down engine goes to like 1600 rpm fuel pressure will not stabilize and goes to like 20 and lower just thought maybe a sensor is acting up elsewhere and kicking the pump off in vst I am gonna check the other stuff first though from prior post.

Oil psi switch will turn off fuel pump. This is so if oil psi falls under a certain psi (usually low like 10psi) he motor ill stop running.

The antisiphon valve will be the straight barbed fitting screwedd into the 90 deg fitting on your tank. IE: what your rubber fuel line clamps to at the tank.

Some are brass, most I've seen are aluminum. There is a spring and checkball inside of them.

http://www.iboats.com/mall/image/view/3/9/moeller_0.jpghttp://www.louisianasportsman.com/pics/p1206462441.jpg

After looking at the check valve ^^^ set up its amazing any fuel at all will flow through there.

well i finally isolated the issue, I swapped fuel lines from side to side off the fuel tank and boom the problem switched sides. so we are going to pull the pickup off and replace what ever needs to be replaced in there along with the check valves. his does not have barbed fittings its all threaded connections with these bigger brass bulb looking things that i assume are the check valves but not sure i have to pull it all apart and see what the deal is.

it was the check valve all gummed up with crap in it cleaned it out checked the other one and boat ran strong

Check vent line before going back to the water , and the fuel line that connects to pump inlet for small cracks .

SB.... nailed that one, well done Sir

Does the USCG require these as oem on all boats? I wonder how many engines have been yanked and rebuilt because of these little buggers. :p

Just pulled a stuck anti-siphon valve about an hr ago. 1988 Wellcraft with single small block. Complained of running fine sometimes and not others. Had to check fuel sender anyway (gauge sometimes reads) and figured what the hell, old boat, and it's right next to the sender on this boat. Ball was stuck a c-hair (yes, a measurement here :) ) open and wouldn't open further nor close shut. Rubber fuel line is in horrible shape too, so good thing boat came in now vs later.

This one has the typical aluminum bodied (as I showed photo earlier) .

I have to pull the pickups it's has more crap in it so I will probably suck the tank out clean everything replace intake hoses and screens

How do you know the pick up's have crap in them ? Do they have screen filters attached ? I would doubt most boats have them, but I have only pulled several and they didn't have'm.

As far as Baja Rooster and the valves....how about drilling them out so spring and ball come out....and then re-install. This makes them look like they are present :)

Cause last week when I took the check valve off it had a bunch of crap in it. I blew it out checked the actuation of it very smooth I put a small hand air pump on tank pick up blew some air into it and reassembled it all ran fine for about a week last night started acting up again pulled valve off again little crap in it cleaned it blew back in tank again runs fine again. So I am assuming crap in tank is clogging up pick up screen and back blowing it is cleaning it up a bit till it gets crudy again. I figured the only way **** like little flies getting into tank is through tank vent.

$10 you don't have the screen and should drill out threaded side of valve fitting so ball/spring come out and reinstall empt fitting. Or just install normal fitting. Water separator/filter will trap the smegma.

PS: maybe you should take that bet. :)

This is a 100 % prime example why you test with a remote outboard fuel tank and primer bulb in line with fresh gas and new fuel line hook at the remote fuel tank side to the first fuel inlet engine side. Been posting this test for years up here. It will tell you if the issues are on the boat side or the engine. Working on boats a lot of times testing is for ruling out what the problem is NOT. Process of elimination. Total cost for this set up is 100 bucks and you use this same set up when winterizing your boat for proper fuel systems lay up using the soup mix.

All boaters should buy this outboard remote tank / fuel line set up and store it in a clean dry place when not in use. Do not keep fuel in it - use that for you lawn mower or whatever. Always use fresh gas that day when you are ready to test with the remote fuel tank set up. RVP plays a huge part in fuel and how well your engine runs depending on the season. Fuel RVP at the gas pumps can change up to 7 times per year depending on your location.

My check valve went missing and I replaced it with a 1/2" barb and fresh line. ;)

NCD, I've got this exact same problem and it sounds like I need to pull my pickups and check the valve and if there is a clogged sock on the end of the pick ups. My question is, what all is involved in pulling the pickups? Is it difficult? Do I need to have any new seals or gaskets ready to reinstall or does it pretty much go back together without any of that? any advice you can provide of what I'm going to see or get into would be appreciated. I'm headed to the marina to check it out tomorrow morning. oh, 1998 Fountain with carb hp 500s. thx, Jay.

Every boat is different I would bring some quality rtv that's chemical resistant at the very least. That way if you need to reseal it temporary you can. the boat i was working on didn't have a screen on the one side pick up and that was the side I was having issues. I had to fabricate new screens for both sides and clean out the tank.

Got it. How do the pick ups remove from the top of the tank? Are there just a few screws or whatever and it just pulls right out/straight up?

Not sure on the fountains and i own a fountain, but never looked at mine I know my sending unit screws into the top of the tank because mine doesn't work anymore. I installed a fuel monitoring system with is way more accurate 99.5 percent to be exact and the system tells me way more info gph, total fuel used , has a reset for current fuel used. My tank is a 120 gallon tank and I know not to burn more than 80 gallons before refueling because fountains tend to not run well at a quarter tank or less. Mine anyway lol.

They are usually threaded in, so make sure you have a tube of Permatex teflon thread sealant or equivalent for when you reinstall.