32-3 fuel tank capacity - overfilling

[nquigley]

I’ve seen specs that the fuel tank should hold anywhere from 19 to 21 gallons. Let’s call it 20. I pulled into a marina on my way down the Tennessee river a couple days back with the fuel gauge at about 1/8 full. I don’t have 100% confidence and it’s accuracy, but let’s start there. The attendant pumped 21 gallons into the tank without fuel coming all the way up the delivery port!
The shoe gauge red full for the next 70 miles, so I figured it was stuck in the full position. Based on known fuel consumption, I decided to add 5 gallons from a jerrycan on deck. After another 10 or 15 miles, the gauge was still reading full, so I decided to visually inspect the level in the tank. I gingerly undid one of the 6 screws for the fuel gauge sender unit assembly and fuel started welling up out of the screw hole. So, my tank is still filled higher than the inset level of that sender mounting. The bad thing is, that ever since that Marina fell, I have had some diesel in my bilges. I would think that the system does not have any overflow vents and relies on the filler spout for that. Am I wrong?

 

[Christian Williams]

I don't know what your tank capacity really is, it might vary a bit by manufacturer. Sailboatdata says 22 gallons.

The issue here sounds like overfilling. A fuel gauge--I don't know what a shoe gauge is--can be eliminated from the troubleshooting, as they are generally relied on only for "more or less," i.e. gross estimates of full or half or getting near empty.

There must be a fuel air vent visible on the hull. On my 38 it's high on the transom. When overfilled, diesel flows out of the air vent, which is how you can tell when a tank is absolutely topped off. An air vent is present on every diesel tank to equalize pressure as the fuel pump draws fuel out.

Topping off, as we do with cars, is not recommended most of the time because it unnecessarily pressurizes all tank fittings, especially the fuel gauge sender unit and the fuel intake hose. It;s better to come close to full, not so full that diesel spurts out of the air vent.

Many of us have found fuel in the bilge after overfilling. It comes from the submerged sender port, which is otherwise never tested for perfect seal.

I would examine that port, and make sure the five screws have a good grip on the aluminum. If not, use larger screws. Change the gasket and reseal with Permatex.

Diesel is hard to get out of the TAFG. It may require using small diameter suction tubes and even drilling drain holes for them, to be resealed later. It can take months of repeated cleaning and detergent rinse to get the red out. I am reminded of this by my tattoo, which says "idiot."

Not a big deal. Tank size is hard to measure exactly, just don't overfill it. The M25 burns half a gallon an hour, 15 gallons is usually plenty.

Notion that tank must be kept filled to prevent water condensation or organism growth has been debunked by Maine Sail and others, and I am persuaded by their arguments. And by not carrying around unnecessary weight, which for the 55-gallon tank of an E381 is 400 pounds at $6 a gallon.

 

[bgary]

Diesel is hard to get out of the TAFG. It may require using small diameter suction tubes and even drilling drain holes for them, to be resealed later. It can take months of repeated cleaning and detergent rinse to get the red out.

When I overfilled my tank (haven't we all?) what worked for me was to line all the bilge-pockets with sorbent pads, put enough water in the bilge so it could slosh around through the limber holes, and then rock the boat a bit to, well, make it slosh. Enjoy all the people coming by stopping to ask what you're doing when you're aggressively rocking your boat at the dock. "I'm rinsing the bilge" seems to raise more questions than it answers <lol>

Over time a surprising amount of red fuel found its way to the pads. When it started to slow down I gradually added more and more water into the bilge with some Dawn liquid soap and let it slosh around, hoping (?) that the combination would rinse the areas under the TAFG that I couldn't get to any other way. Eventually got to the point where there was no more red finding its way to the pads

ObNote, remember to disable bilge pumps before each rinse-cycle, and re-enable them after, otherwise you run the risk of putting diesel through your pump/hoses and out into the water....

B

 

[nquigley]

bgary & Christian - thanks both for your great ideas. We didn’t see any fuel coming out of the air vent at the dock so I wonder how it got down into the bilges, but, anyway… it’s there now - I will stressfully mitigate.

 

[Frank Langer]

bgary & Christian - thanks both for your great ideas. We didn’t see any fuel coming out of the air vent at the dock so I wonder how it got down into the bilges, but, anyway… it’s there now - I will stressfully mitigate.

It's possible for the fuel vent to get clogged with insect nests, debris, etc. It can be removed from outside and cleaned with a wire brush or similar. You may want to check it.
Frank

 

[peaman]

bgary & Christian - thanks both for your great ideas. We didn’t see any fuel coming out of the air vent at the dock so I wonder how it got down into the bilges, but, anyway… it’s there now - I will stressfully mitigate.

There is very little vertical distance between the fill and the vent, and both are well above the top of the tank, so by the time fuel arrives at the vent, the tank is over-filled with no air space. So no surprise that you could run for hours without changing the gauge reading.

 

[Bolo]

As you know the E32-3 specs indicate a 22 gal tank but I think of it as a 20 gal tank to be on the safe side. I like nice round numbers, I guess. Just the other day I checked the tank gauge and it showed 1/2 full which is when I stop at the fuel dock and fill with 10 gallons. I either have my "first mate" call out the gallons as they progress on the pump or have the dock attendant do it. Plus I listen for the sound of the tank filling which does change as it reaches the top and I fill slowly. However, the other day when I was filling the tank there were a lots of swells coming into the harbor causing the boat to rock quite a bit so I asked for a 9 gallon count instead of 10. I've never overfilled or spilled fuel over the side using my methods.

 

[Kenneth K]

As I think you already know, the 32-3 fuel tank has the unfortunate design that the fuel pickup, return, and quantity sender sit in a "cutout" area that is about 1-1/2" below the top of the tank. It could be that the fuel sender senses only the fuel to the top of the "cutout", and no fuel above that level, unless it were specifically set and calibrated to do so.


So, while the tank is listed as 22 gal, filling the tank to capacity puts the "cutout" area "under-water" (and thus, pressurized), which will cause seepage from the fuel sender gasket. If you re-fuel all the way to the top of the fuel cap, you now have added pressure from that portion of the vertical fuel line that rises higher than the tank. Here's what my seepage looked like when overfilled.


As leaked fuel starts to pool along the hull, it first fills the lower inboard corner of the fuel tank cavity. If the level gets higher, it will flow forward under the battery box, then find it's way to the lower, forward areas under the TAFG until it gets to the bilges. So, if you have fuel in the bilges, you likely have at least an inch or more already pooled in the forward part of the fuel tank cavity (the blue circle below).

 

[peaman]

What sort of sender is that, @Kenneth K ? My 1987 Hull 737 only has a simple float gauge similar to this. And it is mounted not in the "cutout", but rather a foot or so aft of yours. It's a pain to check, so maybe I should upgrade to a sender.

 

[Bolo]

The fuel sensor in my E32-3 tank is an actual mechanical float gauge mounted in that notch in the tank. I have to lift the cushion at the Nav station to read it.

 

[Christian Williams]

I don't rely on fuel gauges, but (lately) I like having one in the cockpit. It's an easy install, you just obtain a sensor unit and a readout, the wiring from the fuel tank is easy. If the panel face doesn't offer a hole for a fuel gauge, we can just drill one in the bulkhead or coaming.

Some folks like the gauge at the nav station, but a cockpit mount is good to watch while fueling.

 

[Kenneth K]

What sort of sender is that, @Kenneth K ? My 1987 Hull 737 only has a simple float gauge similar to this. And it is mounted not in the "cutout", but rather a foot or so aft of yours. It's a pain to check, so maybe I should upgrade to a sender.

Just the basic Moeller swing-arm float sender (this particular one from Defender says it's for gas, not diesel). Mine came with the boat.