Fuel Separation

Donald Tyson · Joined: 24 Jul 2023 Posts: 621 Photos: Thistle

Thank goodness My boat is fitted with a Racor fuel filter with a visible separator. Last weekend was only the third time I have used the boat and each time I use it I check the separation bowl for water. This past time, after fueling and boating for a couple of days, I noticed a quarter of an inch of black looking grunk in the separator. So I don't know if the new gas is scrubbing the tanks and loosening up more grunk or if the gas I bought was full of water. The gas came from an otherwise respected provider, Wawa Convenience Stores, which supplies half the trailer boats with gas for the whole east coast. Wawa's are everywhere here.

I have not run the gas out of either tank while in use. In fact I have not run either tank halfway. I simply haven't gone that far. So this gas may be up to two yrs old or more.

At the ratio that came out of the separator there could potentially be many many ounces of separated fuel in each tank. I was figuring to use Star Tron or Sta-Bil fuel treatment therapeutically going forward, as well as keeping a sharp eye on the separator.

How would you handle this situation?

Pretty independent article:
https://www.practical-sailor.com/boat-maintenance/best-ethanol-fuel-treatment-for-boat-engines

Flashyfish · Posted: Sun Aug 03, 2025 10:29 am Post subject:

Drain the black gunk out of the filter and leave it in a jar for a day or so and see if it separates. That might tell you if it is water or something else mixed in.
Run the boat some more and if the black gunk returns, pull and clean both tanks. Replace all fuel hoses between the tank and outboard.

Going forward every fill up should include stabil or other fuel stabilizer.
Alternate tank use to ensure fuel stays as fresh as possible.

Donald Tyson · Joined: 24 Jul 2023 Posts: 621 Photos: Thistle

That sounds like solid advice. I'll have to see about the removal process.

Schuster · Posted: Sun Aug 03, 2025 2:54 pm Post subject:

When I purchased my boat in 2021 it had been sitting for a couple of years. It had the Honda BF150 engine and was the fuel injected model. One of the problems that I immediately encountered was bad fuel, about 50 gallons of it. It apparently was a not treated. It caused the high pressure fuel pump to seize up from rust. Well I learned way more than I really wanted to in the repair of that but was happy to have learned more about the engine.
In the process of getting rid of the bad gasoline I purchased a fuel transfer pump from the local NAPA parts store. They work great and are safe to operate. They are not terribly expensive ($35ish) and I have now used it several times as a refueling device for riding lawnmower to prevent spills.
As far as the hose replacement goes I recently saw that the fuel hoses on the boat should be changed every couple of years. I haven't replaced mine but this makes me think more about it as hoses deteriorate from the inside and you can't see it until it's too late. Probably an inexpensive preventative maintenance item.
If it were me, I would remove the fuel and replace it with fresh NON-Ethanol fuel. I would put the recommended amount of SEAFOAM additive in the fuel and run that thru the motor to clean out the engine of any contaminants that may have entered from bad gas. There are plenty of articles on the comparisons between SEAFOAM and STAYBIL if you do a google search.
I hope that you get your issues corrected and have no damage. It sounds like you're on top of it. Good luck.

Donald Tyson · Joined: 24 Jul 2023 Posts: 621 Photos: Thistle

Schuster,
If I am on top of it it is because of this group. Thanks for the testimonial. Did you remove your tanks to empty them?

-Waypoint- · Posted: Mon Aug 04, 2025 8:21 am Post subject:

After getting the fuel cleaned up. You have to prevent water from continuing entering the tanks. Replace your fuel tank vents with a P-Trap style vent.

https://www.amazon.com/Attwood-Corporation-66419-3-Degree-P-Trap/dp/B001YXO148/ref=sr_1_3?dib=eyJ2IjoiMSJ9.b5b3OBbLDH9NfyyjdmJLClB98VE7HyqX00ePrY8Do5EMfSz6u2gITAYPki36eUVArW21S9Xu24iGTniMBAZeGEgcL7hPRFjMCGhk5iJcE4lSPB8pgQ7dHSI1vfEjCYEcDLYNhOT4i-O5JYIXp5YcSxziKM1zzwoelFmghm--YhXaKHDeMaZ7qr5VQ-fLulG2ZVGNPgFc-l7GT_ToO25zA_NiubM4fYbc8BxCMm1fJGQ.4fEJP_Al5sr0pliaeUSc67vitvCkftvgwmJHJO9JCPE&dib_tag=se&keywords=tank+vent+ptrap&qid=1754309374&sr=8-3[url]

This prevents rain water from being sucked into the fuel tanks by sloshing fuel piston effect by boat movement.

I had this problem with my fuel a year ago. No more water in fuel.

Add dielectric grease to the o rings on the gas tank fill caps.

Donald Tyson · Joined: 24 Jul 2023 Posts: 621 Photos: Thistle

Thanks Mark, easily done. I'm hoping to lear more on this piston effect.
I use the Grease on many electrical fittings already.

Schuster · Posted: Mon Aug 04, 2025 10:44 am Post subject:

Donald wrote:

"Schuster,
If I am on top of it it is because of this group. Thanks for the testimonial. Did you remove your tanks to empty them?'

My tank is a 100 gal tank under the cockpit floor , so no I did not have to remove it. I entered the tank via the fuel sending unit. Remove three screws and lift the float out. When ready just lower the fuel transfer pump suction hose down into the bottom of the tank, fix the other end to a portable gas can and turn it on. It's got an automatic shut off when the portable tank is full. Battery operated. There are several on Amazon.com. Just search for "fuel transfer pump".

Donald Tyson · Joined: 24 Jul 2023 Posts: 621 Photos: Thistle

Schuster and Mark,
Since you both have had issues in this area, and have successfully worked your way through them, I humbly ask if keep an eye on the glass of the separator, and empty it when water shows up, can I safely pull off the ten or twelve days left on my vacation? Since both engines are running fine, and as long as I check the bowl regularly might I finish out the rest of the vacation?

Schuster,
If I feed a siphon hose down into the tank and suck it dry can I assume that I'll get enough of the Grunky water out or must I remove the tanks. I'd like not to have to remove the tanks/clean/replace all valves and hoses until I return in September.

-Waypoint- · Posted: Mon Aug 04, 2025 5:17 pm Post subject:

Absolutely. If you add a can of Seafoam to each of your fuel tanks it will actually separate out the water from your fuel. Water will be at the bottom of the tank where your pickup is. In the morning before you get underway pump the fuel primer bulb. This will be the best time to catch some of the water that has had time to settle overnight. Drain out the water from the filter and repeat until it is clean fuel. If water makes it to one engine it will start running rough. Drain out each carberator bowl. Repeat as needed.

Donald Tyson · Joined: 24 Jul 2023 Posts: 621 Photos: Thistle

Mark, Sounds great then. I'll do it. but I'll be using Startron by Starbrite. I own it as of yesterday (amazon) and is rated very highly for fuel issues. I'll let ya know how it works.
I wonder how much water, in ounces, is in there. Could it be several pints or is is likely just a few ounces. It will be rewarding to take it all apart and repace all the hoses and valves later in yr.
Don

colbysmith · Posted: Tue Aug 05, 2025 12:25 am Post subject:

In regards to pumping fuel out of your tanks. My main fuel filter has two "out" ports. One goes to my main outboard, while the other has a connector fitting for the line to my kicker. I have a small electric pump I purchased from Amazon, that I placed a fuel hose on with a female connector on the "in" side of the pump that connects to that kicker fitting on my fuel filter, and then a small shut off valve on the "out" side of the pump. I use that small electric pump line to drain the fuel left in my tank at the end of the season. (I also use it to attach to a small 3 gal fuel tank I keep in my bilge with pure, or non-ethanol, gas that I can fill my generator from.) The little electric pump isn't real fast, but much easier than removing the gauge sender. Usually takes maybe 15 minutes or so to pump out 5 gallons Colby

robhwa · Posted: Tue Aug 05, 2025 10:53 am Post subject:

I have two steps I go through when I take my CD22 out of the water, for a few weeks or for the season. I have detachable fittings to the Honda 100 which can supply fuel from the main tanks, each about 24 gallons, the middle portable tank, 12 gallons, or the long trip tanks, an extra 38 gallons total. I have a small tank that I "finish" running the Honda on synthetic, alcohol-free fuel. After 10 minutes I detach this and let the motor run out of fuel. To drain the main tanks I use a long hose and a vacuum pump and put the long hose below the lower level of the tanks into a container. The CD22 is on the trailer so it sits high and drains by gravity siphon. I then use the extra fuel in a vehicle. I always run ALL of the fuel out of gasoline motors when stored even for a week or more. This has done well, as I have generators and chain saws that still start effortlessly after many years.

Donald Tyson · Joined: 24 Jul 2023 Posts: 621 Photos: Thistle

Looks like I'll be pumping gas soon.

Schuster · Posted: Tue Aug 05, 2025 4:35 pm Post subject:

Donald, I don't think you'll have to remove the tanks. That fuel transfer pump will almost suck it dry. It's a lot like a bilge pump whereas the spinning impeller is right at the end of the run of the tubing its mounted on. Just lower it into the tank like you would a siphon hose, hit the on button and sit back. Good luck.