FWIW

Ed Schenck · Mar 4, 2011

There might be an advantage to keeping it around twenty gallons. If it is full or near full the diesel will run into the vent hose. Unless you have rerouted the hose the fuel will sit in a low spot and block the vent. On our cruise I had to loosen the gauge and pull it part way out to let air escape. Otherwise it would take about five minutes for every gallon we pumped in. I have not found a way to route the vent hose to eliminate the low spot.

sandpiper10471 · Mar 4, 2011

Good info Bill 1565. This gives me a good baseline even if my gauge doesn't read just the same as yours.
Ed - ditto on the vent hose. This has caused me great aggravation. Hope to solve it this season. If you do it first, let us know please. Sounds like you have already been at the boat. I am still on the ski hill raising money for the summer.

Johnb · Mar 4, 2011

Thaks for sharing - that is helpful information, as was your other post.

malyea · Mar 4, 2011

Not to hijack the thread...

My new to me (can I still say that after 12 months) '82 H30 will burp diesel out the vent if I fill it too fast - anything more than a slight trickle and ... whoops (I pour out of a can 'cause no diesel pumps on my lake...)

I've read two advice items that come to mind and am asking for clarification -

- Always keep the fuel tank full to prevent condensation and water contamination, and

- something about a "vent valve/backflow preventer" that you install in the vent line that allows the venting function but prevents the fuel from burping over the side into the water...

Thoughts?

Ed Schenck · Mar 4, 2011

Over twelve years now and I have never had a full tank(45+) except for one cruise. It sits every winter with whatever, half or third or ??? Maybe I am too trusting of the Racor filter/water separator. The old 2QM20 never quit and neither has the new 3YM30.

When I first came on this board back in 1998 I read all these horror stories about fuel contamination and gunk in the tank. So I cut two big cleanout ports to find an almost spotless 1979 aluminum fuel tank. That was the only time I ever changed out the diesel. Gave it to the marina to run the yard tractor.

Dalliance · Mar 4, 2011

Bill1565 said:
When I boated on Lake Michigan in the '80s all the marinas gave away whistles to install in the vent. You could hear the pitch rise as the tank filled.

Don't know anything about "backflow preventer" are you sure it's a fuel thing, not a holding tank odor filter?

I put a fuel vent whistle on and find it very helpful when I fuel up at the pump. It does not work so well when using a gerry can and filter funnel though.
Also re-routed the vent hose to eliminate a low spot that could fill with fuel and to create a high point above the vent thru hull so water can't run down into the tank.

Johnb · Mar 5, 2011

If you spill fuel in San Francisco Bay you risk crucifiction or worse. I fill slowly from a can with a built in valve and have someone hold a rag or container over the vent.

Blaise · Mar 6, 2011

I too have cut inspection holes in my fuel tank. Unlike Ed, what I found was ugly. I can only assume that what I found was the result of enough fuel being run through it for 10,000 engine hours and thirty years of warm weather condensation. I had gotten to the point that I could not keep my engine running for more that an hour without clogging up $50 worth of fuel filters. What I found when I cut the two six inch holes was almost an inch thick layer of what looked like black course sand. I couldn't even see the fuel pick-up that runs down the deepest part of the tank. After scraping the bottom of the tank, (one of the dirtiest jobs I have ever done) I realized that I couldn't reach all of the tank because of the baffles. I contimplated cutting the top off the tank and putting a flexible tank in it. Instead, I got serious and fired up my pressure washer. If you try this, here's a tip for you. Don't use Dawn dish soap. Use laundry detergent instead. It is inconcievable and indescribable how many billions of bubbles you make with 2400lbs of water pressure. I ended up getting a bucket full of the black crap out of the tank. I think it was algae based. After hours of rinses to get the soap out I let it dry for a couple of days, changed all the fuel hoses and filters and refilled it. So far, lno more problems.

One great thing about this forum is finding out that I am not the only person that suffers with the few design flaw that exist in out boats. If anyone solves the tank vent issue, please let me know. I have always hated that it takes me an hour to take on thirty gallons of diesel fuel.

Jim Legere · Mar 7, 2011

Like Blaise, I discovered "black stuff" in my diesel tank when I cut an access hatch in the top (near the fuel gauge). Unlike Blaise, I had only a couple of coffee cups full to deal with. A few years back I replaced the large fuel filler hose and the vent hose, on recommendation of the surveyor. I replaced them exactly as original. Like other H37C sailors, I have occaisionally had vent burps and slow filling. I am sure the problem is that the vent line goes DOWN from the tank into the bilge, under the hot water heater, before it goes UP to the transom. Fuel collects down there (when heeling to starboard) and either burps out the vent or prevents air from escaping the tank during filling. I think I am going to re-route the vent hose so that it runs without a low point to the transom vent. If I can find one of those whistles, I'll put that on too. Seems like a simple enough solution.

Mathurin · Mar 7, 2011

When we bought the boat, we took the tank out, I would not recommand that ton anyone, we had to remove the bulkhead where the chart table is. But in the end it was worth it, there was some 'varnish' all over the tank plus half a inch of goo down the bottom. So far, we've put 500+ hours on the engine this year without any clog filter issue (and must admit we are still postponing changing it). But we never ever fill the tank from the pump. Whe have 4 gerry cans that we fill, but some biocide then let them sit for at least one day before we feed them (through a filter funel) down the tank. Also we never empty the gerry cans, there are always some deposit down the bottom. A racor fuel filter with a clear bowl is also one on the best investment we made. And by the way, the dirtiest fuel we bought so far was in the states, it seems they made some huge progress in the Bahamas to improve fuel quality. We will see tomorrow if we can say the same thing about the fuel quality in the Turks & Caicos

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