Diesel leak when filling

[megamarine41]

I have a small amount of diesel fuel on top of my port side fuel tank whenever I refuel. There is absolutely no spillage up top and I have replaced the hose clamps attaching the fuel line to tank with stainless contoured clamps. Is there any other possibilities?

Kent megamarine. PDQ 41

[duetto]

hi kent,

don't know 41 but based on 34 there are: 1) vent with overflow preventer. fuel will froth in here even when not a complete refill 2) fuel guage sender 3) fuel transfer pump (not sure 41 has this).

[billp]

Not sure I know the answer just yet, but the local Yanmar expert is coming tomorrow to look at my port engine space and fuel system. On our trip up from Florida (on our new-to-us 41) was all about dealing with water in the fuel tank. Water somehow gets past our dual Racor 500s and fills up the on-engine filter on the port engine which sets off the "Check Engine" alarm. I had to drain water out of the Racor bowls and on-engine filter several times a day during the trip, more when it was rough.

While the above is a separate issue from the one you post, the Yanmar fellow specifically wants to look at the vent, hoses, and the overall fuel system to see where water is getting into the tank, again only on the port side. Maybe our issues are related...water in, diesel out. An installation issue???

Will let you know what we find out.
BillP on Spitfire, PDQ 41

[billp]

Kent,
We went through the fuel system on the port side and it is so straightforward that it has to be a leaking from the hose. It is a vertical run from the combined fuel fill/vent and the two hoses down to the fiberglass tank and there is simply no other way for fuel to pool on top of the tank.

We also determined that any water in the tank got in from someone's error rather than a fault of the boat's builder. Whatever water I found in the port tank (at least several gallons) must have been put in the tank at some point during construction or during previous ownership.

Maybe one of the hose fittings has a burr or other obstruction on it, and the clamps are sealing completely.
BillP

[SecondWind]

Water condenses in the tank out of the air (It is vented), due to temperature changes (cooling at night) after a humid day. you will find some amount of water in all fuel tanks, hence the use of fuel water separators (Racor's). There are water removing additives (alcohols) but I don't recommend them. Every once in a while the tanks just need to be completely drained and cleaned out. Bill, if your boat sits in very humid conditions, I would expect a large amounts of water to condense during that time period, especially if the tanks were not kept full. The greatest precaution is to keep your fuel tanks full, thus allowing no room for air which contains moisture. It is highly unlikely that anyone put water in your tanks.

[billp]

Terry,
Our local engine guys (Bayshore Marine, the top Yanmar dealer on Chesapeake Bay) said people mistakenly put water in fuel tanks all the time, and their techs have to run contaminated fuel through a portable heavy-duty polishing system regularly to remove both water and the microbial junk that collects.

They also told me that fiberglass tanks in fiberglass hulls create a nicely insulated situation that makes condensation much less of an issue than with other boats. As the water was only in the port side tank, it also is highly unlikely it was put in at a fuel dock, as both tanks are used by the engines and filled at the same time.

We will never know where the water came from unless it occurs again, which I will be watching very closely. And as the on-engine filter/separator on the Yanmar BY260 is where the water collected to set off an alarm ("water in fuel") we will upgrade the Racor 500 filters. They catch water but still pass on quite a bit (about two cups per day on our trip north), apparently overwhelmed by the draw of the engine's fuel pump.
BillP

[SecondWind]

Bill, Good place to go, I trust Bayshore Marine and dealt with them exclusively when we had our Yanmars. We used a commercial fuel polisher twice, before I removed the tank and cleaned it (ours was aluminum). I finally built my own fuel polisher using a fuel pump and a large Racor filter and ran it weekly and prior to every sail. We now have a fiberglass tank in our keel which also makes condensation less likely since the water temperature is nearly constant, however I still get some in the Racors.

Possible sources on any boat are leaky fuel cap seal (contaminate water will be fresh), backflow from the vent (Water could be fresh or salt depending on the boat location), condensation (still a factor in humid climates), contaminated fuel (we use a water separating funnel in areas where fuel is suspect, especially if it is drawn from barrels), cracks in the top of the fuel tank or hoses (highly unlikely), and accidentally putting a water hose in the fuel filler. We never allow someone to fuel our boat without watching the operation and making sure that only diesel goes in the tanks.

In addition to your existing filters, I recommend that you build and install an on-board fuel polishing system and use it to remove any water before you run the engines. It sure made life easier for us.

[duetto]

"I had to drain water out of the Racor bowls and on-engine filter several times a day during the trip, more when it was rough."

this strikes me as a LOT of water that probably didn't come from condensation. if it were condensation alone, then many pdq's would be having major water problems and i'm not hearing they are. hopefully it was a one time mistake. if it wasn't, you'll know soon enough.

[billp]

Thanks for your comments, Terry. I had a fuel polishing system on our previous boat (a Zimmerman 36 and the system barely fit) and we never had any fuel problems. It was a quality ESI system. I may consider installing one as we get the rest of the boat figured out, but hopefully the bulk of the water is gone. We ran the big polisher for six hours on each of the two tanks.

You are right, John, this may just have been a one-time mistake, and I will know for sure if it never happens again.

Unfortunately, we didn't solve Kent's original question in this thread.
BillP