Fuel Tank Size Discrepancy

[wingtime]

You should be able to syphon fuel out of the tank even thru the fuel filter. You have a restriction. My bet is on the antisyphon valve on the fuel tank. It is a check valve built  into what looks like a hose barb where the fuel line attaches to the tank. Take that sucker off and toss it. Replace it with a standard nipple.

The Harbor Freight syphon kit and the red hand pump kits work good.

[Capt. Bob]

Just curious really since you were having trouble siphoning the fuel. Primer bulb location (fore or aft of the filter/water separator) is in the same league as battery type and conductor sizing. Many opinions.

I drain my tank every winter and use the gas in my son's truck or my motorcycle. I have a dedicated pickup for this but still use a primer bulb to start the siphon. Following on Wing's advice, I would too drain the tank and confirm that it is drained since you may be experiencing a fuel issue but....

Your issues with the bulb may indicate some underlying problem with the pickup or possibly a stuck/clogged anti-siphon valve (if equipped) on the pickup itself. Bad bulb too. You may wish to also confirm an unobstructed vent hose.

In any case, again draining the tank removes the "bad fuel" from the poor running equation and helps determine the tank size if you can't find a sticker or get actual measurements of same.

If you decide to drain, I would suggest that you remove your fuel line before the filter/separator and place the primer bulb at that spot. Then purchase clear vinyl hose of the correct size from Lowes/HD that will reach from the bulb to the ground (over the transom is how I run mine). The clear hose is sacrificial (although it lasts a couple of times before yellowing/hardening) and allows you to see the fuel flow. You can start with a small gas can but depending on the amount, as Wing stated, you'll need a drum of sorts. I have two 30 gal. drums (plastic) that I use.

Never hurts to replace the fuel if suspect.

Good luck.

[Capt. Bob]

Oops, 
Wing beat me to it.

[wingtime]

I drained over 30 gallons out of my tank using the method Bob mentioned by attaching a clear tube to the end of my primer bulb.  Of course since you have a restriction that probably won't work.

I will say that a fuel supply restriction can be a big problem.  Besides poor performance it can cause a lean running condition that can destroy an outboard in short order.

I also agree that if the fuel is suspect I'd drain it. 

I feel your tank is holding the full capacity of fuel.  You just can't get it out.  My bet is when your mechanic drained it, he just drained it until it stopped thinking it was empty.  When in reality the restriction stopped the flow.

[daniel123]

Thanks, Guys. This is just the type of information I have counted on this site to provide over the years -- and is very much appreciated. 

I have confirmed that the tank is a 50 after locating the stamp saying so.

It seems to me I checked that barb for an anti siphon feature and found it was not fitted with such, but I'll check again. I'll look in my records, but believe I actually purchased a replacement at WM with the pickup attached, and saw that the original was not an anti-siphon type, and if I replaced it, I would have used a non-anti siphon model.

The primer bulb is new and seemed to be sucking ok. I will go get the clear hose and drain the tank pre-filter.

My mechanic said he drained the tank via the fuel sender port, not the fuel line, but I'll confirm that.

Questions:

If he did go straight into the tank from that port, and didn't use the fuel delivery system to drain it, where does that leave me? Using that method, he should have been able to see/know when it was completely empty, and not be fooled by a clogged fuel delivery line, right?

If he did use the fuel delivery line to drain the 50 gallon tank, what are the odds that both times the restriction would kick in to leave 24 gallons in the tank? Both times I refilled it, it took 26 gallons to top off. 

If not the barb, what could cause the restriction? I see no kinks and the hose is new 'tween the tank and the filter, after being replaced when we found the interior lining had deteriorated in an (Attwood EPA Compliant Cephline890 USCG Type B1-15 SAEJ1527 attwood 89-06 CANADA) line that was only one year old. (I've replaced that tank-to-engine line twice now). 

[daniel123]

Looks like I did confirm that I did not have an anti siphon valve in my original barb and replaced it anyway in 2012 with a new no-siphon barb and pick-up.   

[daniel123]

I just had a thought. My shop just confirmed that they drained the tank via the sending unit to be able to get all the gas out, so that eliminates any fuel line/pick-up position variables. Both times that I refilled the empty tank the Osprey was on a trailer. I stopped filling it when I could hear gurgling (and yes, gas spitting...but I was on asphalt, not Pine Island Sound) out the vent. I always figure that means the tank is full and stopped pumping, and noted it took 28 gallons but it didn't really register at the time that it should have been closer to 50. The first time it happened, year before last, I did note it, but didn't push the point with the shop as it was drained by a new guy (who has since been fired) and there were larger issues with the repair (like replacing a BRAND NEW, top of the line Moeller water separator/filter with a cheap Sierra one that stripped free of the housing the first time I checked it and screwed it back on).

Anyway, based on the trailer angle, vent issues, etc., could I have actually not completely filled the tank when I thought I had topped it off? I know better than to count 100% on the fuel gauge (which is new and appears to be  working ok) but it showed full when we launched. If I actually had only pumped the tank half full I think it would have shown that, but maybe not. It's just weird that both times it took exactly the same amount of fuel to top it off, and I'm thinking that's no coincidence. Could that be it? Pilot error at the fuel pump?

[wingtime]

That all depends on where the vent fitting on your tank is located (aft vs FWD etc). Even so if it is aft it would take a heck of an angle for 26 gallons to co e up hugh enough for fuel to spit out the vent. What did the gauge read?

[daniel123]

Vent is FWD and gauge read full after I pumped 26 gallons into the supposedly drained/empty 50 gallon tank. But like I said, I've learned not to trust those fuel gauges -- although mine is new and has a new WIMA sender so I have little reason not to.

[arndtb33]

did we get this figured out My problem sure sounds identical

thanks