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Fuel in Bilge Issue

Old 05-09-2019, 03:52 PM
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Default Fuel in Bilge Issue

Well, finally going to start a thread on this to see if anyone has any suggestions on how to troubleshoot.

Boat is in my sig, 2006 Bull Dolphin 22 Tournament.

Has two 50 gallon tanks, one in front of console and one behind. Both have access panels above them, boat are lightly foamed in additional to the bulkhead screws.

Boat deck drains to bilge and pumps out due to deck height, so it's it's effectively a wet bilge, of course it is "rinsed" out from washing boat down and rain. In any case.

About 18 months ago, I began having an intermittent issue.

Would get fuel fumes in the console, air it out, and all is well. Would not come back for a month or more of regular use, have gone 6 months and 75 hours without issue resurfacing, including full tanks, hard running in seas, etc.

After having the issue twice in as many weeks, pulled both hatches above both tanks, checked all hoses and clamps, re-bedded both sender plates, replaced all feed lines going to racor in the bilge, all new clamps, etc. Currently still has original fill and vent hoses.

The tanks both hold pressure with vent fittings sealed, they both vent with the vents open.

I can threaten to pull the boat and throw it on the trailer, pull the tanks and all hoses, and the problem then resides for months.

What I am relatively certain is:
1. Fuel is coming from forward of the rear bilge bulkhead
2. Fuel vapors and extremely light sheen will appear generally while the boat sits in the water overnight, while tanks are mostly full
3. I have run off of one tank or the other for a couple of months and thought I had isolated the issue to the unused tank, only to shortly after have the issue randomly appear again. This has happened running off both front and rear tank exclusively for a few weeks or months of use.
4. Immediately upon smelling fumes, have run my hand along the underside of all feed lines in the rear bilge access, both going to the tanks, going to outboard, and under the racor canister itself as well as re-bedded the threaded fittings in the racor housing itself. Nearly certain it's not in that area.

What I am curious of:
1. Can fuel tanks hold pressure yet still have a seam crack that opens under random conditions?
2. Is there any scenario where even a half full tank can burp fuel while boat is resting at dock in the water overnight in a totally still canal?
3. Can anyone suggest anything short of ripping out both tanks and all lines at this point?
​​​​​
I am a methodical problem solver, and have been trying to isolate variables on this issue with literally no progress at all. It does seem to happen more often after filling from a pump (as opposed to cans), but it's always the next day or next week, and never immediately after filling or immediately after running in hard seas etc.

Spells, incantations? Anything?

Thanks for sticking with me through the long read.
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Old 05-09-2019, 05:53 PM
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Pressure testing is usually a good test. Where did you block off the vents? At the tank or at the hull side? Any chance that you have a leak(S) at the hose to vent connection at the hull side and expansion etc is letting fuel drip back down? Only other thing I can think of would be to vacuum test the tanks as well in case there is a crack etc that holds under pressure because of how that distorts the tank.
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Old 05-09-2019, 06:05 PM
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Originally Posted by Aliboy View Post
Pressure testing is usually a good test. Where did you block off the vents? At the tank or at the hull side? Any chance that you have a leak(S) at the hose to vent connection at the hull side and expansion etc is letting fuel drip back down? Only other thing I can think of would be to vacuum test the tanks as well in case there is a crack etc that holds under pressure because of how that distorts the tank.
Good thought on the vacuum testing. What is a safe way to vacuum test? Hand pump only I assume, or maybe vacuum pump from air compressor?

As for blocking vents, I blocked at hull side. I have this style vent:
https://www.westmarine.com/buy/white...9?recordNum=53

And used some Wikki Stix from my kids to lay in the circle opening to seal it. Actually worked extremely well if anyone else is looking for a way to block off a similar vent.
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Old 05-09-2019, 06:37 PM
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Normally when pressure testing tanks we use a clear pipe full of water connected to the breather so you can measure the inches of water displaced rather than relying on a pressure gauge. That way you can't over pressurize the tank and it is very accurate even at low pressures.. I haven't tried, but I imagine you can do the same thing with a water pipe but having it lifting the water rather than pushing it to vacuum test? I normally adapt a tyre valve or similar so that I can use a hand pump to pressure test, but if using the water method you can safely use a small electric pump. To pull a vacuum, one of those hand pressure/vacuum testers that they use for outboard and stern drive gear cases would probably be a good choice.
You are doing all the right things, just ave to keep at it. Any noticeable pattern of leak vs fill level on the tank? How long did you hold the pressure test for?
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Old 05-10-2019, 06:32 AM
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It seems to be more common at higher fill levels, but I have now seen it at 1/2 tank or less. Right now both tanks are a little under 1/4 full so if I wanted to work off one or the other for awhile it would be a good time.

I just repeated the pressure test to be sure, both tanks hold 2 psi with no drop in pressure over 5-10 minutes. Had to repeat on the rear tank as it had a slight pressure drop due to one of my fittings leaking in my ghetto pressure test device. Held pressure fine after that.

Each feed line going to the racor has a small ball valve, I'm wondering if keeping them both open would allow them to bleed any pressure from a momentary restriction in venting etc over to the other tank? I've always run one open at a time... The vent fittings are tough to get to inside the gunnels, I suppose pulling those hoses and clearing them along with the fittings couldn't hurt.

I've considered emptying one completely as a next step short of pulling them. The vacuum test sounds nice though, will see if I can give that a shot, though probably not until next week.

Was hoping to run the boat down to the Keys along the Gulf coast in July, so if it needs a tank replaced the clock is ticking...
​​​
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Old 05-10-2019, 06:37 AM
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Have you noticed a difference if the tanks are half full, near empty or full?

I had a leak from the sending unit gasket and the tank was full.
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Old 05-10-2019, 08:14 AM
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Have you checked the gasket around the fuel sender?
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Old 05-10-2019, 08:25 AM
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Hello, before pulling the tanks etc. You send you bedded the sender plates, you mean the base of the sender unit to the tank, what did you use, replacement gaskets are available. Having gone through a similar problem on a diesel boat, after much searching with torches etc, the deck was pulled up above the tanks (this boat had a large removable section above the tanks if they ever needed pulling), the tanks had more than one fixing for a sender unit and another fitting on the other tank for a tap off for a generator (not fitted), turned out the genset fitting was loose, when filling to the top and navigating the diesel spilled and stank up the engine room and left a sheen. Im wondering if you have tanks that might other fittings, maybe for other fuel fill hoses. Now its happening when the tanks not full, how hot is it where you are, any condensation? Hope this helps.
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Old 05-10-2019, 12:42 PM
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I used the blue Permatex fuel resistant gasket dressing compound and re-used cork gaskets.

May go ahead and put new cork gaskets in since I haven't re-bedded the deck plates over the tanks yet.

I really should go around with a bright light and mirror and make sure there aren't any capped off bosses or fittings on the tanks I'm unaware of, that would be a really logical and satisfying fix for this thing if something was a little loose

It seems to be more prevalent in winter months with big temp swings, and usually happens overnight, where you go from blazing hot to cool... So maybe contracting fuel pulls in on something that causes it to weep?
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Old 05-10-2019, 01:33 PM
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If the tanks are plastic you will get fumes.
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Old 05-15-2019, 12:07 PM
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Unfortunately they are both aluminum tanks, would be great if it was just some weeping plastic.

Last time we saw issues, scenario was as follows (this was about a month ago):

Fished all day Friday (bait fished before tournament), probably 10 engine hours, left St Pete with both tanks around 3/4 full, ran them both down to about 1/3 full, then put about 30 gallons into the front tank and a little extra into the rear tank, off of a pump at a marina (this around 9PM). Ran about 15 minutes from there to my buddy's house where the boat was to stay docked overnight. Moving around the boat cleaning up and rigging/organizing for a few hours after we got back, all is well, penned the bait off the side cleat of the boat so checked on it around 2-3AM, all is well. Neither tank was topped off, but front tank nearly full.

Go down to the boat for final prep and to move baits back into the well around 445AM or so, and overwhelming fumes in the console. Air it out and they become weaker, but still present. Small sheen in the bilge, let it all evaporate and go on with the day, and all is well. Fish in some pretty rough stuff, and no further issues. Fished all day, probably 12 engine hours by the time we arrive back at my dock, and all is well.

So in this scenario, the issue surfaced in a dead glass calm tiny canal, while sitting, after it had been sitting already for probably 5 hours. What gives? There's a temp swing involved there, probably 80+ degrees to 70ish, but where could fuel sit that wouldn't be vented and contract to where it would allow fuel to escape into the bilge?

Currently, I plan to run off the rear tank only for a few weeks, and top it off almost completely, leaving front tank nearly empty... See what happens. Any thoughts on methodically isolating variables would be welcome.
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Old 05-20-2019, 06:23 PM
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Well, during the time I pumped out the front tank into the rear tank, I saw a short section of feed line that I didn't replace last time (only replaced the clamp on the end that goes to the ball valve, this line runs from rear tank pickup to the ball valve.)

I didn't think a whole lot about it at the time, and actually today had Absolute come out and test both tanks. Both tanks tested good by their methodology, and so I was back to square one.

Fiddling around on the work bench today, I saw a pinhole wearing into the little old section of hose from the outside, which somehow I hadn't noticed when replacing it? Maybe caked with dirt? Anyhow it was just sitting randomly there on the bench.

Sprayed it down with some soap and water, and sure as shit it bubbled from that tiny spot with some pressure.

I need to double check to see if there is a screw point pushing through where the hose runs, or what did it.

But right now, I think I have a smoking gun. Will follow through on previously planned methodology of topping rear tank off and leaving front empty for a bit, then top off front tank and see if we are all good to go.

Thanks all for your input, it has been helpful and has been appreciated. Will update with an all clear if this is all it was.
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Old 07-03-2019, 08:09 AM
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Well just to further update this, I had realized the hose in question had a fuel tank deck plate screw that was pushing into it. Problem solved, right?

However, it seems that was not all.

I lost the lower unit on the boat (water intrusion into gear oil), and it has been set up on the trailer for awhile. Finally put it back into commission this past weekend, and took the opportunity to top up the front tank and re-connect it while it was on the trailer. While running with front tank empty and rear tank topped off all the way for a few weeks time and 20ish hours since that last post, never had even the slightest sniff of fuel fumes.

After splashing it following the fuel stop, we ran it the rest of the day without issue (Sunday), and found fuel fumes in console and droplets in the bilge water Monday AM. I have the hatch off of the front tank, and there is no evidence of fuel anywhere on the top. Totally dry on the fill/vent hoses and fittings, totally dry on feed fitting, totally dry around the sender. I thought maybe it had pushed out the sender gasket and since evaporated... So let it all air out and evaporate, was good to go by the afternoon sitting there. Tuesday morning, same thing. Checked earlier in the morning this time, and it's apparent that none of the fittings/hoses are leaking.

At this point, it has to be the tank itself.

The front tank cannot come out of the boat without cutting. I'm thinking of taking the route of cutting the tank. Will suck if I find that it is intact upon removal, but would rather do that than cut any glass in the boat at this point.

Anyway, what a shit show. Leaving the boat at home for our week in the Keys that I've been trying to plan for a few years now. Will get front tank pumped out before we leave. We will see if a final kick in the nuts awaits me during that process.
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Old 07-03-2019, 08:45 AM
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Boats suck.

Enjoy your Keys trip and forget about that thing for a few days.
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Old 07-03-2019, 08:52 AM
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EricF,
I had a similar issue with my Pathfinder 23DV. the issue was with the fill hose.
The fuel fill hose had a pin hole and every time I refuel, gas ended up in the bilge. After pulling out the fill hose, the only way I notice the hole was by plugging 1 end of the hose and putting water on the other end of the hose.
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Old 07-03-2019, 09:14 AM
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Pressurize the Tank,then spray everything down with a Dish Detergent water mix.You may get lucky,the Soap solution will make bubbles even at the smallest leak..Naturally,You may not be able to check the bottom or sides. But give it a shot.
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Old 07-03-2019, 08:18 PM
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Thanks guys. Will pull the vent and fill hoses before cutting the tank, I think that is a fair thing to do.

​​​​​​Lone Ranger, when the tank company did the pressure tests, we sprayed everything we could reach/see with a soap/water mixture. No bubbles on anything.

We did cap at that time at the fill and vent fittings on the hull, so it included the fill/vent hoses. But obviously something is leaking that held 3 psi or whatever they pressurize to. Maybe a hose? My guess is a crack, but won't find out right this minute.

Will try to bail some dolphin and yellowtails and have a nice cold beer or seven in the pool while pondering in the Keys

Thanks!
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Old 07-03-2019, 09:06 PM
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Just FYI I had a very similar issue with a previous boat and ended up damn near blowing myself up... seriously.

Occasional smell of gas, no gas in the bilge, checked all hoses, fittings, tank, etc and everything checked out.

Was a couple miles offshore with it one day and shut off the motor to fish a pggy pod, after about ten min I hit the ignition to move on and every door blew open, every latch broke and all my leg hair was burnt off.

Turned out out there was a few small pinholes in the top of the tank. Quit running that thing until you get it fixed.
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