Fuel Tank Algae

Oct 4, 2008
147
Hunter 36 Mulberry Cove Marina
I have a 2004 H36 and since I bought it I have had recurring fuel problems. Every year I have to get my fuel polished because of excessive algae growth. My neighboring boats (Catalina and Beneteau) are rarely experiencing fuel issues. I’m wondering if this a common problem with the Hunter tanks. Before you ask or recommend I keep my tank topped off.
 
Jan 11, 2014
12,957
Sabre 362 113 Fair Haven, NY
The problem is bacteria, not algae. Algae is a plant that requires sunlight, I doubt sunlight reaches your fuel tank. Bacteria consume diesel forum colonies which is what causes the problem.

Has your fuel tank been cleaned, not the fuel, the tank itself?
 
Jan 7, 2011
5,592
Oday 322 East Chicago, IN
I had a Hunter 280 for about 5 years, and never had a problem. I did add some fuel treatment (biobor IIRC) every winter at haulout when I filled the tank).

Nothing particularly unique about a Hunter tank. My current O’Day 322 also has a poly fuel tank, and I do the same treatment in it…no issues going on 10 years now.

Have you checked the ring on your fuel cap? Keeping water out of the tank is important.

It may be time to have the tank cleaned.


Greg
 
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Mar 19, 2014
3
hunter 426DS Northport
Good Day to you.
I will try to be brief about your question BUT it will be worth it.
I have a 2003 42DS. When first bought me and 6 members at our club collectivly had our fuel polished.
The result was out of the 6 mine was the most dirty. Gave us the additive to use ongoing and you should have no problems.
Three years later, and a starved fuel line shut down we were Sea Towed back to mooring and I had enough.
I do everthing else on the boat why not this. My new racor was loaded with the brown gunk.
I had to see inside my tank to get to the root. If i cut a hole into the tank was there a bonified access device. Yes. Pics below. Pics below will show what the tank looked like and what i have to get rid of. End result cut the 8 inch hole, phsically cleaned tank by hand, intalled the acces port, and no problems for the past 6 years.
Can now examine my tank each season and have peace of mind that this won t happen again.
In closing pics below show bank of tank which is where it fills from and front of tank where it sucks from. You will see the sludge and the pick up sticks just waiting to suck up that gunk. There are three. Engine Generator and spare. I don t have a pic of the additve that i still use but i will send when I get back to the boat.
Hope this helps
Happy TrailZ
 

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Jan 11, 2014
12,957
Sabre 362 113 Fair Haven, NY
Good Day to you.
I will try to be brief about your question BUT it will be worth it.
I have a 2003 42DS. When first bought me and 6 members at our club collectivly had our fuel polished.
The result was out of the 6 mine was the most dirty. Gave us the additive to use ongoing and you should have no problems.
Three years later, and a starved fuel line shut down we were Sea Towed back to mooring and I had enough.
I do everthing else on the boat why not this. My new racor was loaded with the brown gunk.
I had to see inside my tank to get to the root. If i cut a hole into the tank was there a bonified access device. Yes. Pics below. Pics below will show what the tank looked like and what i have to get rid of. End result cut the 8 inch hole, phsically cleaned tank by hand, intalled the acces port, and no problems for the past 6 years.
Can now examine my tank each season and have peace of mind that this won t happen again.
In closing pics below show bank of tank which is where it fills from and front of tank where it sucks from. You will see the sludge and the pick up sticks just waiting to suck up that gunk. There are three. Engine Generator and spare. I don t have a pic of the additve that i still use but i will send when I get back to the boat.
Hope this helps
Happy TrailZ
This is the answer. There is gunk in the bottom of the tank.

The photos show what I assume to be 2 supply and 1 return line terminating very close to the bottom of the tank, this will compound problem. With the return line at the bottom, it will stir up any sludge making it easier for the pick up line to pick up the sludge. Making it a few inches shorter will reduce the turbulence it causes. The pick up lines should be a little shorter, about an inch above the bottom of the tank, this will cause some capacity loss but will also reduce the chance of the fuel line sucking up the gunk.
 

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
23,143
CAL 35 Cruiser #21 moored EVERETT WA
I have had recurring fuel problems. Every year I have to get my fuel polished because of excessive algae growth.
My neighboring boats (Catalina and Beneteau) are rarely experiencing fuel issues.

I’m wondering if this a common problem with the Hunter tanks.
No, it is not a boat tank problem but a fuel management problem.
Algae happens when you get water into the fuel system. Water gets in from the place you purchase the fuel or from leaks (like the "O" ring on the fuel fill inlet). Check out Practical Sailor Magazine. They have a fresh article about the fuel problem.

Annual Fuel polishing is expensive. Maybe once, after that, it is all about management. Fuel additives are helpful.

A fuel system like the Keenan system can pay for itself.
 
Sep 11, 2011
426
Hunter 41AC Bayfield WI, Lake Superior
One thing to check are the fuel vents. On our boat, there was No top loop on the vent fitting so, rain and deck washing had the potential to get into the tank. It came from the factory that way.
 
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Jan 11, 2014
12,957
Sabre 362 113 Fair Haven, NY
Algae happens when you get water into the fuel system.
Some bad information just refuses to die. Algae is a plant. Like all plants it needs sunlight to grow, it can not grow in side a fuel tank.

What does grow is bacteria and other microbes. These critters live in the interface between water and fuel. They grow from colonies and die leaving sludge. One particular group of microbes feed on sulfur in diesel fuel and then excrete a sulfur based acid. This acid gets trapped beneath the colony and against the metal fuel tank causing the tank to corrode in a process known as MIC, microbiologically induced corrosion.

Water can get into the fuel tank through contaminated fuel, rotted or missing O-rings on the fuel cap, or through the vent line.

The use of BioBar JF with every tank will keep the microbes at bay.

Raising the fuel supply lines above the bottom of the tank will help prevent the sludge from being sucked up into the fuel system.
 
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wpatch

.
Apr 8, 2022
19
Hunter Hunter 36 Baltimore
Hello,

I also have a 2004 Hunter 36. We fouled our filters our first day coming to home dock. I can give a pretty fast/easy fix that has lasted for four years.

1) Unload fuel tank. (Pull sender unit out of tank and you can get a fuel transfer pump into the hole.) We were full so 35 gallons.
You could have that fuel polished, but we just donated it to the fire department. You get access by removing the bed, and the hatches in the floor of your rear birth.
2) Remove subfloor (It's a lot of screws, but doesn't take a ton of time.) Once completed you need to disconnect the tank and vent on the stern side, and the fuel hose to the engine. (Good time to replace fuel lines while doing this).
3) Take the tank out and clean it out. I used a hose to get the gunk out. I then coated the entire inside of the tank with anti-foul stuff.
4) Replace both fuel filters. (I toyed with putting a electric fuel pump here...didn't do it yet).
5) Getting the tank back in takes a bit of muscle. I found stern and vent + filler hose first, then muscle in the fuel line.
6) Once everything is reconnected you now have air in your lines. Bleed from the injectors.
7) We now only fuel up from busy truck stops/gas stations, never fuel docks. We also strain the fuel on the way in, then use fuel transfer pumps to fuel. I am consistently surprised how much gunk is in the bottom of the fuel cans. Diesel isn't the same as it used to be.

Feel free to reach out. Happy to help. (We ended up having to replace our starter also after this) It sounds like a lot but its a pretty easy job.

wp
 
Jan 11, 2014
12,957
Sabre 362 113 Fair Haven, NY
Take the tank out and clean it out. I used a hose to get the gunk out. I then coated the entire inside of the tank with anti-foul stuff.
What kind of "anti-foul stuff" did you use?
 
Jan 11, 2014
12,957
Sabre 362 113 Fair Haven, NY
STAR BRITE Star Tron® Gasoline Additive, 16 oz. | West Marine is the stuff I use. I used an entire bottle dry coating the inside of the tank. Then ratioed on refill. Finally when I add fuel I ratio it in each top off.

wp
The link you sent was for the gasoline version, I hope you used the diesel version.

The Starbrite product does not prevent microbe growth. For that you need a biocide, like BioBar JF. While there is often some particulates in diesel, the big culprits for sludge are is water microbes.
 

wpatch

.
Apr 8, 2022
19
Hunter Hunter 36 Baltimore
yeh I may have overkilled:p The having to dock without engine our first-time coming home was traumatic. (I even regularly carry a 5 gallon so I can re-route and use it as a temp fuel tank) Also why I want to add in a electric fuel pump to make bleeding faster and easier.
 

JamesG161

SBO Weather and Forecasting Forum Jim & John
Feb 14, 2014
7,770
Hunter 430 Waveland, MS
Find a reputable Marine Diesel Filler, which normally put Biocide in their Fuel

Jim...
 
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Oct 4, 2008
147
Hunter 36 Mulberry Cove Marina
Thanks everyone for your replies. I had my fuel polished, replaced both fuel lines, replaced both filters, and I have installed a clam shell cover over my vent to prevent water ingress.
 
Sep 25, 2008
7,435
Alden 50 Sarasota, Florida
Thanks everyone for your replies. I had my fuel polished, replaced both fuel lines, replaced both filters, and I have installed a clam shell cover over my vent to prevent water ingress.
Didn’t clean the tank walls?