fuel system gremlin

JaCrispy

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I keep having issues with my fuel system, 1988 5.7 Alpha One I/O. No fuel to the carb. I thought I had it narrowed down to the pump then it stalled again over the weekend. I opened up the line at the carb, cranked the engine, no fuel. I replaced the water separator/filter (heard a small hiss) and it ran fine after that.

Backing up a little...I thought I was having fuel gauge issues and maybe water issues and pumped all the fuel out of my tank. Out of a full tank, 45 gal, I got about 1 gallon of water.

Also, A few weeks ago I couldn't fuel up and found the vent line had a bunch of water in it.

1) If the separator gets water in it, does it completely clog starving the engine of fuel?

2) Are there any vent options so I can move the vent from the side of the boat out of the way of any water spray?

Right now, I'm looking into one of those separators where the bottom half is a clear cup so I can monitor any contamination. Fuel would go through that, then the current filter and up to the carb.

Work done: new fuel pump, new separator, rebuilt carb, checked fuel pickup tube, good o-ring on tank fill cap.
 

JaCrispy

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Also, this boat is new to me, only had it out 3 other times. And one of them I broke down. ha
 

Fleetwin

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The "hiss" is indicative of a fuel starvation issue, as you figured.

1. Your vent line may have a bow in it. It must run straight from your tank to the outside vent. No DIPS. A dip is a place for water to collect and stop venting much like a "p" trap under a sink.
2. To check for venting issues, run the boat with your fuel cap loose.

About the only other possibility is your anti siphon valve on your tank outlet. Those can stick but it is rare.
 

JaCrispy

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I did open the fuel fill cap but heard the 'hiss' noise after when I swapped filters. I think both the fill and vent do somewhat bow down after the tank then go up to the transom area. I'll try to reroute the vent first.

I actually snapped the anti-siphon valve removing the fuel pickup tube last week. I temporarily replaced it with a regular brass fitting (new anti siphon in mailbox today).

Is there a fuel pressure gauge I can mount between the carb and line?
 

airshot

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Your tank vent line needs to have an uphill loop in it, that uphill loop raises above the vent opening and this is what keeps water from entering vent line. Had the same problem a few years back with water in the fuel. Discovered the vent line was full of water and it was running into the tank. I picked up an extra long tube for new vent line and created an uphill loop and problem solved. Just recently had an issue with excess water in bilge, looking all over for leaks only to find water backing in thru bilge pump outlet. Again an uphill loop in the discharge line stopped water entry and that problem was solved.
 

JaCrispy

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Took it out again last night and I think I figured out the problem.

Just cruising, 1/2 throttle or so, it runs fine. If I hammer down, it will stall after 10 seconds or so. I can blow into the vent on the side of the hull, air goes in and air comes out. I can also open the gas cap and nothing changes. But when I crack the fuel filter I hear a "hiss", which makes me to believe the rubber fuel line between the tank and filter is collapsing. I'm going to swap it out over the weekend and (weather permitting) do some testing.
 

NHGuy

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You are right, got to be. There's a blockage creating a vacuum in the line which dissipates with time. It's more of a problem when the motor wants more fuel.
ps. awesome screenname!
 
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JaCrispy

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After replacing the rubber line I was able to run WOT normally....for the first hour or so. Then it started the same scenario. WOT, boat stalls, crack the fuel filter loose, hear a small "hiss", boat starts and runs fine 3/4 throttle and under.

The rubber line has a slight curve in it, like the letter J. Not a tight bend at all, more like extra slack, but it does curve. I was going to try to reconfigure it to get a straight shot from the filter to tank. If that doesn't work out I'm going to make up a steel line, flare the filter end and have only 3-4" rubber line to connect to the tank.
 

Bondo

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After replacing the rubber line I was able to run WOT normally....for the first hour or so. Then it started the same scenario. WOT, boat stalls, crack the fuel filter loose, hear a small "hiss", boat starts and runs fine 3/4 throttle and under.

The rubber line has a slight curve in it, like the letter J. Not a tight bend at all, more like extra slack, but it does curve. I was going to try to reconfigure it to get a straight shot from the filter to tank. If that doesn't work out I'm going to make up a steel line, flare the filter end and have only 3-4" rubber line to connect to the tank.

Ayuh,.... See if it'll run right, on a remote tank, plumbed to the filter,..... Eliminate yer tank, completely,...
 

Fastatv

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Your tank vent line needs to have an uphill loop in it, that uphill loop raises above the vent opening and this is what keeps water from entering vent line. Had the same problem a few years back with water in the fuel. Discovered the vent line was full of water and it was running into the tank. I picked up an extra long tube for new vent line and created an uphill loop and problem solved. Just recently had an issue with excess water in bilge, looking all over for leaks only to find water backing in thru bilge pump outlet. Again an uphill loop in the discharge line stopped water entry and that problem was solved.
I would also do what this man suggests^^^^^^^^^^^^^^. Until I did this on two of the I/O's that I have owned, I had continuous water in fuel issues.....
 

NHGuy

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When it gives you the problem try loosening an end of the line between the separator/filter and the pump, or the line between the pump and the carb. If one of those gives you the hiss you might isolate the vacuuming section that way...Have you dumped the separator contents into a glass container? I'd do that each time now. I don't know if those filters stop flowing when they contain too much h2o. It wouldn't surprise me though. Maybe your fuel separator is holding things up.
 

JaCrispy

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Thanks for the replies.

I emptied my fuel tank a few weeks ago and removed about 1 gallon of water. That's when I checked the pickup tube, replaced the anti-siphon valve. I've replaced the separator 3 times and only ran approx 55 gallons of fuel through since I've owned the boat.

The current vent line runs under the deck in the engine compartment and up to the thru hull vent. I was able to bring the hose up a little but there's not enough slack so instead of opening Pandoras Box pulling the hose out I just ordered a new hose. When it comes in I'll route it properly.

I tried cracking the fuel line on the carb when it stalls but nothing happens. Only when I crack the filter loose I hear the hiss and it fixes itself. I bought an inline pressure gauge but the vac gauge is a good idea too. Didn't think of that.
 

JaCrispy

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just wanted to update this thread, as I found the problem with my fuel system was the Wix/Napa fuel filter I was using. I have a business account with my local Napa and have just been using their stuff (when possible).

I installed a Merc filter and the boat runs perfect, no stalling out. I contacted Wix to see if there was something inside these filters like a valve or something but there is not. So I chalked it up as the Wix/Napa filter just does not provide the fuel capacity for the engine.
 

Bondo

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just wanted to update this thread, as I found the problem with my fuel system was the Wix/Napa fuel filter I was using. I have a business account with my local Napa and have just been using their stuff (when possible).

I installed a Merc filter and the boat runs perfect, no stalling out. I contacted Wix to see if there was something inside these filters like a valve or something but there is not. So I chalked it up as the Wix/Napa filter just does not provide the fuel capacity for the engine.

Ayuh,.... I'm findin' that hard to believe,....

I run Napa/ Wix filters in a fleet of boats, 'n a fleet of dumptrucks, 'n a fleet of heavy equipment,....
Wix filters are some of the Best I've found,.....

I know Napa has a few numbers for the Merc replacement filters,...
Some of the different numbers are for different length filters,...

I buy the #3225s, 'n run 'em on the entire fleet of boats,...
I just found it's rated at 10gph,....

Did ya inspect the Contents of the filter ya took off,..??
 

JaCrispy

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Yeah, I've never had problems with their filters either. I think that's the number I was using, but even with a brand new filter it still stalled. I've replaced it about 6 times thinking it was from junk in the tank. Today was my second time out with the Merc filter and still no issues.
 

achris

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...

I buy the #3225s, 'n run 'em on the entire fleet of boats,...
I just found it's rated at 10gph....

And there's the problem right there. 10 gallons is 38 litres. My engine (4.3MPI) at full noise is sucking 62 litres per hour! (I have a flow gauge). That's 16.4gph.....A 350 is probably going to pull a few more than that.... 'Nough said...
 
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Bondo

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And there's the problem right there. 10 gallons is 38 litres. My engine (4.3MPI) at full noise is sucking 62 litres per hour! (I have a flow gauge). That's 16.4gph.....A 350 is probably going to pull a few more than that.... 'Nough said...

Ayuh,.... I guess I'll have to google it again, maybe the "h" is an "m",..??

It'll take all the fuel a 3/8" line can run at fuel pump pressures,....
 

JaCrispy

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Yeah, prob 10gpm. Either way, the filter doesnt work. I still have one brand new Napa filter left over. I can try that one, now, after the merc filter. If I get the same situation its definitely the filter. Like I said, I never had problems with Napa stuff, but the Merc stuff is marketed as high flow. Whatever that means.
 
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