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Left Gas Cap Off in Rain

Old 12-24-2018, 08:51 PM
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Default Left Gas Cap Off in Rain

Somehow in a momentary lapse of consciousness I left my gas cap open on the boat. I found it today about a week after putting about 25 gallons in it (110 gallon tank).

of course it's been windy and rainy for the entire duration so no doubt quite a bit of water and possibly tree debris has gotten in there.

I'm thinking about hooking up a fuel polisher/water separator to it and cycling the gas through that. Sadly these are brand new tanks and the gas is fresh. Total about 30 gallons of fuel in there. Thoughts.
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Old 12-24-2018, 08:58 PM
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Heavy rain and no cap could equal 1 gallon of water. You got to get it out somehow. Can you take the feed line to the engine and pump it out?
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Old 12-24-2018, 09:19 PM
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Methylated spirits (metho) mixes with water and gets asborbed than runs thru the fuel system.
try a cup of gas(petrol) and metho and see what it does if you're sceptical.
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Old 12-24-2018, 09:23 PM
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Imagine a drinking glass left outside on your patio for that period.

How much water would have filled that glass? An inch? Two or three? It is the same amount that got into your fuel tank. I would surprised if was more then a few ounces. Let the water separator do its job is my vote.
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Old 12-24-2018, 09:42 PM
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Drain the gas, mix in some metho and run a gallon or two at a time in a car or truck.
If you have accessible tank sensors that can be removed or an access port, look in the tank for debris.
A cheap Lizard Cam or something similar will really help with the inspection.
Any remaining debris will be caught in the filters, change them frequently for 6 months or so.
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Old 12-24-2018, 09:52 PM
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Originally Posted by peter bear View Post
Methylated spirits (metho) mixes with water and gets asborbed than runs thru the fuel system.
try a cup of gas(petrol) and metho and see what it does if you're sceptical.
doesn't work unless you drain the tank and add a few gallons of metho, the second you tip metho in petrol (gas) it instantly mixes and does not reach the water in the bottom, you will need to get a syphon hose right to the bottom, maybe through the gauge sender? even using the fuel pick up will not get it all out because it is well short of the bottom by design, in short, nothing you can just pour in the tank will absorb a decent amount of water.
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Old 12-24-2018, 10:05 PM
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Run it slowly through your racor and it should seperate all but a few drops
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Old 12-24-2018, 10:10 PM
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Hopefully you have only straight gas in there so you can pull the tank level sender as suggested above and pump out from the tank bottom (ideally tipping the boat & tank for the hose to reach the lowest point to which the heavier water would gravitate ) until there is no evidence of water settling out in your samplings.

If you have any gasohol in the tank , don't bother with the above, it would all have to be removed and discarded ( rcycled) , not "polished" ot treated , as it would have phase-separated into just 2 layers of engine-damaging liquid. Good luck & Merry Christmas.
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Old 12-24-2018, 10:25 PM
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Mr common sense here with this post.
Completely agree.
There’s is no way I would be doing any draining or anything crazy on this situation.





Originally Posted by captbone View Post
Imagine a drinking glass left outside on your patio for that period.

How much water would have filled that glass? An inch? Two or three? It is the same amount that got into your fuel tank. I would surprised if was more then a few ounces. Let the water separator do its job is my vote.
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Old 12-24-2018, 10:34 PM
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Originally Posted by captbone View Post
Imagine a drinking glass left outside on your patio for that period.

How much water would have filled that glass? An inch? Two or three? It is the same amount that got into your fuel tank. I would surprised if was more then a few ounces. Let the water separator do its job is my vote.
Pi x radius (of the filler cap) squared x inches of rain = volume in cubic inches of water ....easy enough to estimate if you have an approximate rainfall.
However, some of that may have been absorbed if you are using E10, causing a slight octane drop.
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Old 12-24-2018, 10:52 PM
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Is it inboard or outboard?

First, you should already have a racor.

Second if its ob, just tilt boat/tank so pickup is at low pt (easy on trlr), squeeze bulb and catch in jar.

If you got ethanol gas, may have no free water anyway.

I pumped 10 gal of water out a tank before.
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Old 12-24-2018, 10:58 PM
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It is standard pump gas (ethanol). I typically go through gas fast enough not to worry about it.

it has been a solid downpour. Still pissed me off I did this. Guess I'll cycle it through a water separator.
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Old 12-24-2018, 11:08 PM
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Marina gas is reknowned for being contaminated with free water. This is why all boats need racor. You can see it in the clear bowl and drain it off. When you have to remove another type to dump it.....gas everywhere .
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Old 12-25-2018, 01:59 AM
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Yep, as stated above. E10 gasoline will absorb about 3-4 teaspoons of water per gallon. The water is already mixed with the gasoline. The best thing to do is use the fuel pronto to avoid phase separation. You may want to add some more alcohol to completely keep the water in suspension. Your Racor or separating filter will not catch the water when in suspension. Don't let it sit and separate. Use it up soon.
Side note: Polar solvent hydrocarbons, such as alcohol, ether, ketones, benzene, toluene, xylene and some others, are miscible in water and hydrocarbons. They are what allow water and fuel to mix. Even straight non-E10 gasoline has enough polar additives to absorb some water. The best gasoline is AVgas. Pure Alkane fuel.
....sorry, got sidetracked a bit.
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Old 12-25-2018, 03:43 AM
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Wouldn't all of these estimates of amounts of water depend on the orientation of the filler neck (vertical, horizontal), wind direction, rain amount, etc? Even if he got 6 inches of rain over the week (highly doubtful), how much water is that in a 1.25 inch opening? What is the capacity of a separator?

in any event, unless there is a water drain channel leading right to the filler neck, I highly doubt that any draining or significant issue exists here. I would run it and enjoy.

EDIT: ..and Happy Festivus to all.
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Old 12-25-2018, 03:52 AM
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Originally Posted by SeaPro48 View Post
Pi x radius (of the filler cap) squared x inches of rain = volume in cubic inches of water ....easy enough to estimate if you have an approximate rainfall.
However, some of that may have been absorbed if you are using E10, causing a slight octane drop.

SeaPro nailed it. Unless there is some feature on the boat that acts like a funnel and directs water toward the filler cap (which would be a terrible design), the only water getting through the cap would be the amount of rain that actually fell on the opening. I'm betting teaspoons or less. Run it!
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Old 12-25-2018, 05:48 AM
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You can get a paste for determining the extent of water in fuel. Smear on a thin metal rod and run down through the pickup tube. See what you read to determine water content. If significant, I would try to tilt the boat so fuel accumulates toward rear of tank and use a pump to remove all of it. Then add some fresh fuel (10 gallons) with a water absorber and run that through your racor filter to remove anything left behind. Good luck!
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Old 12-25-2018, 05:54 AM
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There was also an old test of separators (both the standard kind and Racors) that listed how many oz of water these can hold. I think it was on the Whaler site....
I would not worry about this either, given how much could have gotten in. Most I might do is remove the sending unit and pump out like a gallon from the bottom, put some of that in a mason jar and let it sit...
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Old 12-25-2018, 05:56 AM
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I’d just pump the tank dry dispose of the fuel and call it a lesson learned. Figure 250 bucks. I’ve had my fair share of water in fuel and it won’t usually show its ugly face until you are 6 miles offshore.
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Old 12-25-2018, 05:59 AM
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I would pump the fuel through a fuel-water separator and put it in my car that gets a lot of use, so it gets burned up quickly.
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