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Sending Unit Leaking

Aug 23, 2020
5
Catalina 310 Mamaroneck
Hi -- I've discovered that the flange attaching the sending unit into the tank is slowly leaking diesel. I overfilled my tank (drastically overestimated my fuel consumption) and now that flange is leaking diesel into the aft bilge. I filled it so much, diesel came out the vent line.

I've tightened down the screws holding the flange in place and it seems to have stopped, but I'll know for sure tomorrow when I go back to the boat (she's on the hard and has been winterized).

I intend on siphoning / pumping some diesel out of the tank to lower the level below the top of the sending unit before doing a full scrub of the boat. A few questions:

1) I've ordered a replacement gasket from Catalina Direct but it will take a few days to get here. Is there a faster place to order from? Catalina Direct doesn't list the manufacturer

2) I plan on pumping diesel out using a small tube down the main fueling line. Does anyone know if there's anything in the line to prevent siphoning? Will this work?

3) A friend suggested using Depends (adult diapers) to soak up any spillage. Any other ideas?

4) What should I use to get rid of the smell, as I'd like my wife to return to the boat next Spring? :)
 
Oct 22, 2014
13,362
CAL 35 Cruiser moored EVERETT WA
2) I plan on pumping diesel out using a small tube down the main fueling line. Does anyone know if there's anything in the line to prevent siphoning? Will this work?
You really do not need to insert anything. Just take the fuel line off near the filter. Attach your pump to the end of the fuel line. Run a hose from the pump to your container and pump away. You may find that the fuel is under pressure and it will start coming out of the hose all by itself. In that case just put the hose to the container and let the fuel flow no pump needed.
 
Jan 4, 2006
3,136
Hunter 310 West Vancouver, B.C.
1) I've ordered a replacement gasket from Catalina Direct but it will take a few days to get here.
Do yourself a huge favor and DO NOT use a gasket under the flange. The last one developed a leak and you can be sure this one will soon have a leak as well. Nothing leaks like petroleum fuels.

Instead use Permatex #2 as a sealant WITHOUT a gasket. Ensure both faces (either plastic or metal) are as clean as possible before proceeding. Guaranteed for life.

Fuel Tank Pump Out Fitting.JPG
 

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Dec 28, 2015
920
Laser, Hunter H30 Cherubini Tacoma
The only way to get rid if the diesel smell is by getting rid of the diesel. A heavy duty degreaser and a stiff brush. Vacuum out with a wet/dry vac.
 
Aug 23, 2020
5
Catalina 310 Mamaroneck
Thanks for the feedback everyone - I'm hoping to attach the manual pump directly to the fuel line near the filter as @jssailem suggested and I've ordered Permatex #2 as @Ralph Johnstone advised. I'm bringing both auto-absorbent pads and some of those adult diapers my friend told me about, along with some industrial bio-cleaner from home depot to be sure all the diesel is gone. Replacement parts (the gasket and teh permatex) don't arrive until later this week, so I'm hoping the current gasket works once I lower the amount of diesel in the tank.

As this is my first boat (just boat her in August), any advice on opening the flange today and re-using the existing gasket? I'm reluctant to do that and, as long as there's no leaking, just leave it until the replacement arrives.
 
Oct 22, 2014
13,362
CAL 35 Cruiser moored EVERETT WA
I would just pump the extra fuel out.
Save it to pour back in to the tank later when you have room in the tank.

Soak up any in the bilge with the absorbent pads and dispose of the pads. Use the Oil Eater to clean the surfaces of the bilge. Then PurAyer to deal with the smell of diesel in the boat.


Going forward better math regarding fuel consumption and perhaps leave a little extra room in the tank rather than filling it like a car might be advised.
 
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Likes: Alansails
Jul 27, 2011
4,139
Bavaria 38E Alamitos Bay
As John described, I could also empty my fuel tank by removing the primary fuel filter. I have a fuel cock just up stream. Close the cock, remove the filter, open the cock and diesel flows out by gravity. Of course, you need some way to collect the fuel. Not much room in there so a pathway out might be needed..
 
Last edited:
Apr 10, 2010
14
catalina 30 Dartmouth, nova scotia
Here in Nova Scotia, fuel oil furnace service techs use a powder to cover a fuel oil spill when working on your furnace. It absorbs the liquid as well as the odour. Presently unable to get a product name but it sure does work and clean up with a vacuum cleaner. A call call to an oil burner service company or tech should prOvid an answer.
 
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Likes: Kings Gambit
Dec 28, 2015
920
Laser, Hunter H30 Cherubini Tacoma
A couple years ago my tank developed a leak that put about 8 gallons of diesel into the bilge. Most marinas will furnish white poly pads for spills free. Once I got the fuel out I degreased then used a small electric power washer on it. The key is removing the fuel and it’s traces or it will stink forever. That includes impregnated wood. My leak had been going on for years unknowingly soaking into the 1” plywood platform the tank was on a turn it let loose. It all had to come out. No more smell. I’ve use PureAir a lot and I don’t believe it will touch any of it if there is any fuel residue left.
 
Jan 4, 2006
3,136
Hunter 310 West Vancouver, B.C.
Replacement parts (the gasket and teh permatex) don't arrive until later this week,
Any big box hardware stores near you ? Permatex is pretty common stuff.
any advice on opening the flange today and re-using the existing gasket?
Not a whole lot of confidence there. The gasket may come off in little pieces depending on what it's made from.

Once the fuel level is reduced, maybe try positioning (and holding in place) rags around the flange to catch the occassional leakage. If you can get the level down to less than 1/2 tank, the slopping shouldn't be too bad.
 
Jan 17, 2013
365
Catalina 310 St. Simons Island, GA
Been there, done that. My fuel tank sprang a leak during our cruise last March. Lots of diesel in the bilge. Then we had the fuel tank replaced in the summer when we got back and the new fuel guage sender leaked like crazy when I overfilled the tank. Literally pouring out of the tank and into the bilge. We used some kind of liquid sealant and I again accidentally overfill the tank and the leakage was very minimal. The lesson I learned is to not overfill however I did this repeatedly with the old fuel tank for the past 7 years and never had a leak.

Regarding your question, don't try to remove the smell until all of the diesel has made its way into the bilge. Otherwise you will be doing it again. From my experience it takes a long time for all the diesel to eventually flow into the bilge. I am talking about a week at least. I used bilge cleaner, a brush and lots of fresh water. Also put absorbent pads under the fuel tank and in the forward part of the bilge to catch any residual diesel before it gets into the bilge. A couple of cleanings followed by completely drying out the bilge followed by adding more thecleaner and the smell is gone. My bilge fills up when it rains so I poured cleaner into the dry bilge so that when rainwater came in it washed it out. Worked and don't have to do that anymore. I dry out the bilge after every rain event to try and keep the bilge dry.

The new sender on the new tank was very inaccurate and when I told the person who installed the new tank he said it must be the gage. So I replaced the guage with the OEM version from Catalina Direct and it is no better! Full tank reads just over half. Worthless fuel guage system so I continue to use engine hours which is very accurate. My experience with the guages is that the OEM versions are very good and better than some other brands but for fuel with a 310 it doesn't seem to matter.
 

Tom J

.
Sep 30, 2008
1,691
Catalina 310 Quincy, MA
Thanks for the feedback everyone - I'm hoping to attach the manual pump directly to the fuel line near the filter as @jssailem suggested and I've ordered Permatex #2 as @Ralph Johnstone advised. I'm bringing both auto-absorbent pads and some of those adult diapers my friend told me about, along with some industrial bio-cleaner from home depot to be sure all the diesel is gone. Replacement parts (the gasket and teh permatex) don't arrive until later this week, so I'm hoping the current gasket works once I lower the amount of diesel in the tank.

As this is my first boat (just boat her in August), any advice on opening the flange today and re-using the existing gasket? I'm reluctant to do that and, as long as there's no leaking, just leave it until the replacement arrives.
Your fuel tank is above the level of the Racor filter, so fuel should flow when the hose is removed. Remember to close the fuel line valves at the tank before removing the inlet hose to the filter. I don't see any need to remove the flange until the new gasket arrives.
 
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