How Is Water Getting In My Gas Tank?

[Noob2U]

We have a 16' aluminum Monark fishing boat and just got it home from the shop for the second time this year. 2 different boat shops. Both found an exhorbitant amount of water in our gas tank and neither could figure anything with the design that was causing it. Both honestly seem to believe someone is adding water to our tank. I find it hard to believe because:
1. We have no enemies that we know of
2. Someone would have to enter my yard without waking my dog and causing him to bark
3. They would have to be willing to remove the cover to get to the fuel filler door...AT LEAST TWICE

Is anyone familiar enough with this type of boat that can figure another reason we're getting water in the tank? The latest mechanic told us we had about 4 gallons of water in our full tank.

The mechs could not find any other way water is getting in. The obvious pooling water in the transom, hoses/lines, have been checked out.

We've spent over $1000 in repairs this year and I've been laid off...so I have time to camp out in the back yard overnight with the shotgun if I have to.:mad: but want to research all possiblities first. Will be hitting the police station tomorrow.

[Jimbo1490]

Condensation.

[Noob2U]

4 gallons of water accumulating in a 13 gallon tank over a period of 2 months cannot possibly be condensation.

[Jimbo1490]

Maybe it was pumped in at the gas station. Happened to me at least twice.

Jimbo

[mydauphin]

Happen to me last week in a diesel truck. I went to complain and apparently alot of others did to, they gave me $20 off next fill up.

[Noob2U]

Thanks. I'm not too sure about that since we don't always fill up at the same station and we fill up at the same gas stations we fill our cars at with no problems. Plus, here is a sequence of events:

April: Boat died on the river. Took in for service. They said over a gallon or two of water was in there and the only sense they could make of it was that someone added it. They drained it and added 5 gallons of gas.

May: Boat taken out a few times, no more gas added after the service on it because the motor wasn't used much. Most of the use was at idle and no wake speeds, though. Ran fine.

June: Stopped at a gas station on the way to a fishing trip. After 5 gallons, it registered full. Boat died at full throttle on Lake Huron. Ran OK at idle and no wake speeds on the way out of the harbor. Ended up being towed by some nice guys with an even smaller boat than ours.

Now: Took it to a 2nd mechanic referred by some serious boater friends, figuring the 1st was incompetent; hoping the 2nd guy will find the REAL problem. The 2nd mechanic says someone must be adding water to the tank, there was 4 gallons of water in our full tank. It's only a 13 gallon tank!

After doing the math, we're more convinced that someone is messing with us.
5 gallons of gas at 1st shop
-1 gallon burned on a couple short trips
+4 gallons of water added by some jerk
+5 gallons of gas added by us
= 13 gallons

We're baffled. We have no known enemies. It's definitely not a boat to be jealous of. We're fairly quiet and keep to ourselves. We're wondering if some animal rights or environmental activist thinks they're doing the world a favor by sabotaging boats. We live in a fairly liberal town. Will be filing a police report tomorrow and hooking up a trail cam in the back yard. I plan to catch the bastard.

The only other option is that somehow 4 gallons of water seeped into the tank while on the water...but then you'd think I'd have a gas leak.

Thanks for putting thought into this, guys. It's driving me crazy.

The boat will be at a relative's until we are ready to snag the little punk.

[CDK]

If the filler cap has a damaged O-ring, dew and rain may enter there. A little bit each days amounts to quite an amount after a month.
The tank ventilation should have a provision to keep water out, a small rubber flap or a plastic ball. But I've also seen vents without any valve, allowing water to enter the tank on choppy water.

These are the most obvious culprits.

I once had my 90 gallon tank filled very early in the morning because we had a long trip ahead. One engine died 5 minutes later, so we returned to the nearest shore to drop the anchor but never made it because the other engine also stopped. Carbs, filters and water separators contained only water, I had to pump out a bucket full.
If you are the first customer of the day, you get all the condensation of that night. Gas stations also have water separators and the attendants could prevent this from happening. But some don't care.

[Stumble]

Noob2u,

While possible I just can't see anyone doing this on purpose. It sounds to me like either condensation or that their is a leak in the gass line allowing rain water to get into your tank somehow. To reduce condensation just keep the fuel tank filled all the time, this should reduce the amount of air available to wick moisture out of. The next step would be to check the fuel fill cap and ensure it is getting well sealed, and that when the boat is on the trailor that water isn't collecting or running over the fill cap.

[kenJ]

If you are running the standard 10% ethanol mix, it loves to suck moisture out of the air. A good fuel supplement like StarTron will help keep the fuel fresh. But I agree with the others, there must be something the mechanics missed for that amount of water to get in there.

[apex1]

Before you shoot a neighbour bringing back the borrowed drill: does your tank probably have a separate ventilation (not the filler cap labyrinth)? And if so, where does it end?

Regards
Richard

[marshmat]

I have to concur with everyone who's said it's unlikely someone is intentionally watering down your gas. Doing so would be a lot of effort (and there's a dog in the way) for no real purpose. Much easier for a random miscreant to sabotage some piece of construction equipment, or maybe a fire hydrant, or some other easy target.

Because of the condensation issue, it's always good to keep the tank full. But even a 1/4 full tank can't hold enough moist air to produce the amount of water you're talking about. If it were just a condensation-in-the-tank issue, you'd be looking at a cup of water, not a few gallons. And many, many people in northern Ontario cottage country leave half-full tanks in the shed for our entire 8-month winter, with ethanol-blended gas and no stabilizer, usually without any issues.

No, this has to be liquid water finding its way in from somewhere. The filler cap, filler neck and vent line would be the first place I'd look- is water ponding at the filler or vent? (They're usually designed to shed water when the boat's floating, but on the trailer, she'll be down 5 degrees by the bow- possibly enough to trap water where it shouldn't be.) Use a watering can or garden hose to check, while the boat's sitting in its storage position. Don't count on a cover to keep her dry.

If you were ingesting bilge water through a leak in the tank, you'd expect fuel to be leaking out as well- your bilges would stink of gas, and something would probably have exploded by now.

If you just have a tiny crack somewhere in the tank or the line, though, it may not appear to leak. But when the fuel pump starts up, the tank is under negative gauge pressure. If the vent line is clogged, every tiny crack or pinhole- even those too small to leak on their own under the relatively minuscule hydrostatic pressures generated within the tank- will start sucking in whatever's on the other side (read: bilge water). You may have a few of these tiny pinholes and cracks, small enough that surface tension stops them from leaking, but large enough to admit water given a sufficient pressure differential. Pressure testing the fuel tank (with no fuel in it!) might reveal such minor leaks. If present, the tank and/or line would have to be replaced.

Best of luck.

[Noob2U]

Wow, Thanks for all the input. My God I'm waffling back and forth on this one and late last night was back to "no way someone is doing this". It would be SO much easier to mess with our cars or house. Easier to scratch or spray paint or throw eggs.

I'm going do a little more investigation on the boat. This is the first year this has happened, and it's happened twice already. It's just too weird.

[mongo75]

you can always drip some candle wax on the tank cap, so that way if someone opens it to sabotage you, you can tell.

[marshmat]

(Lit candle) + (Gas tank of unknown integrity) = ?

[apex1]

you can always drip some candle wax on the tank cap, so that way if someone opens it to sabotage you, you can tell.

Well, that solves the problem quite immediately!

(Lit candle) + (Gas tank of unknown integrity) = ?

Matt mathematically its = solution.............
well, practically too.

[Noob2U]

OK so I allow gas to pool around the fuel fill door then take a candle to it...right? check!

(just kidding)

We have a list of ideas to catch the culprits and determine tampering but, I'm finding it so hard to believe.

This is what I know. Water Wins. The boat is about 8 years old and I'm afraid something has dried out/rotted/eroded over time and it's probably something that would cost more to get to than the boat is worth.

[FAST FRED]

If the tanks are below deck , folks from the BRONX would use crazy glue to install a few double edged razor blades in the area of the fuel cap.

EZ to check at the local emergency room to see who came in with GUSHERS!

FF

[mongo75]

YES, a lit candle is safe around a gas cap. Jeez, as smart as most of you guys are I sometimes wonder- here's why. (1) the cap is sealed, so no vapors escape (2) gasoline vapors are heavier than air, so therefore they do not go up to the lit candle, but away from it. So before y'all go running around yelling the sky is falling, remeber your science class.

[apex1]

(1) the cap is sealed, so no vapors escape (2) gasoline vapors are heavier than air, so therefore they do not go up to the lit candle, but away from it. So before y'all go running around yelling the sky is falling, remeber your science class.

To your (1): it is not! usually the cap has to act as a tank vent, through a labyrinth!

to (2):
read:
OK so I allow gas to pool around the fuel fill door then take a candle to it...right? check!.

A gas pool of course will ignite immediately.
so far to the being smart comment.......................

[mark775]

He's already done the most obvious - greasing new O-rings and installing caps tight. Maybe it's the bug/flame screen in the vents. Is the water in both tanks? Does the engine have a fuel cooler? That's a likely culprit if so...and they aren't even needed in temperate or cool climes.

[ancient kayaker]

If vandalism is not the cause, with two mechanics not able to figure it out the real cause is an obscure one. Try to find out when it happens -this may enable the mech to diagnose the problem correctly next time.

Water is either getting in during a trip or while it's sitting on the trailer, and it's either a background activity or a sudden event that can be linked to an external cause.

If you can get a dip tube or other device that will detect water down to the bottom of the tank a regular intervals and before and after a trip, you may get the vital clue. At the least you should monitor the indicated level regularly and especially after rain for unexplained increases and to estabilish if it is gradual or sudden. The amounts of water you have experienced should show up clearly.

[FAST FRED]

Not all boats will vent with the tank cap, most with fixed tanks will have a vent line that goes overboard.

Could this outside vent be installed upside down and work as a rain catcher?

FF

[apex1]

Well thats why I asked:
Before you shoot a neighbour bringing back the borrowed drill: does your tank probably have a separate ventilation (not the filler cap labyrinth)? And if so, where does it end?
Regards
Richard

[mongo75]

To your (1): it is not! usually the cap has to act as a tank vent, through a labyrinth!

I don't know if gas caps are made different in Germany, but I have NEVER seen a cap in the US that has given me any kind of impression that it will not seal 100%- no vent what so ever. Hence every tank having an overboard drain.

[pistnbroke]

water in tank easy ......stop pissing about ....

[apex1]

I don't know if gas caps are made different in Germany, but I have NEVER seen a cap in the US that has given me any kind of impression that it will not seal 100%- no vent what so ever. Hence every tank having an overboard drain.

You should look in boats, not helicopters! Others have seen that..........

Not all boats will vent with the tank cap, most with fixed tanks will have a vent line that goes overboard.
Could this outside vent be installed upside down and work as a rain catcher?
FF

[naturewaterboy]

My 2 cents worth is that your tank vent is letting water in if the water gets in while using the boat. But I'd check both the fuel fill hose and the vent hose, and check the tank. Another likely location is the fuel level sender assembly - it mounts in a big hole that is screwed onto the tank with a gasket. With the amount of water you are getting, sounds like maybe the gasket is bad or missing a screw, and the tank top holds water, funneling it into your tank.

[Luckless]

Rather than going back and forth on the issue of a candle flame near a gas tank, why not try an option that doesn't involve a candle? A small dab of caulking, or a tiny strip of red construction tape will do just as well.

[naturewaterboy]

What would a strip of tape do, and what is chalking? :confused: I like the suspense of candles near gasoline - you live life to the fullest when your close to death!:D

[powerabout]

fill the tank right up to just below the filler cap and then wait to see what happens

[Luckless]

What would a strip of tape do, and what is chalking? :confused: I like the suspense of candles near gasoline - you live life to the fullest when your close to death!:D

Chalking is what you get when you write stuff when you're tired and talking to someone about an art project.

But either way they're options for detecting tampering with equipment. And actually chalk would be another good option to use.

[FAST FRED]

"And actually chalk would be another good option to use."


But not as satisfying as razor blades and crazy glue!

FF

[Luckless]

"And actually chalk would be another good option to use."


But not as satisfying as razor blades and crazy glue!

FF

I prefer tamper detection devices that don't send me to the ER if I forget about them. Maybe that's just me however.

[ancient kayaker]

So Noob, what has been happening lately?