Fuel fill venting issue

[h2omansd]

I have a 25 C-Hawk with the Perko fuel fill/vent combo and everytime I gas up at a marina pump, the vent spits out after a few gallons, then settles down for the balance of the fill-up. But, the kicker is that it will never allow me to get to within 7 gallons of the full 110 gallon tank. I can see the fuel in the fill line looking full to the top, yet I know there are 7 gallons remaining. If I don't use a gas dock and use 5 gallon cans instead, let's say when I'm down 20 gallons, I can get all 20 gallons in. I've tried just barely pressing the handle at the gas dock, cannot seem to get around the issue. Is it purely a breathing/vent issue when the vent is part of that combo fuel fill/vent perko unit? would it be better to have a traditional vent line to the side of the boat, separate form the fuel fill cap?

 

[seabob4]

Re: Fuel fill venting issue

First, you want to check that vent line, make sure it doesn't have a "belly" in it. Second, keep in mind that the fuel nozzle at the station or marina pumps at a lot more pressure than you can muster pouring a 5 gallon container in.

But I'm with you, I hate those "combo" gas fills. Cheap little pieces of crap. I'd get a separate hullside vent, and make sure to run a loop in the vent hose that comes back down to the vent...

 

[rwidman]

Re: Fuel fill venting issue

........... I can see the fuel in the fill line looking full to the top, yet I know there are 7 gallons remaining. .........

How do you know there are 7 gallons remaining?

Often, fuel systems are designed to allow an air space for expansion. The fill fitting is not in the top of the tank, but on the side near the top. I suspect your fuel sytem is designed this way with the 7 gallon air space.

The combination filler and vent system is fine. As posted above, make sure there is no dip in your vent hose and that is is a short as possible and runs uphill all the way.

 

[h2omansd]

Re: Fuel fill venting issue

thx. by loop in the vent hose, what exactly do you mean? Right now, the vent hose runs parallel on top of the tank for about 2 feet to the inner side of the boat, then elbows and up about 18 inches into the nipple on the fill cap/vent port. Would it basically run the same, only connect to the hull-side adaptor that I would install? thx again. sd

 

[h2omansd]

Re: Fuel fill venting issue

thx Ron. I know the 7 gallon thing since I have an accurate fuel management system. So, I burn about 7.5/hour. I ran for 4 hours, knew I'd be in the 30-32 gallon range. Gas dock enabled me to put in about 24 gallons. The, went right to my house/lift, burning nothing really. Could then take 7 gallons from 2 cans and filled it up. I did this twice over a 2 - weekend period. I emailed previous owner who said he had same issue for the 6 yrs he had it and lived with the situation. Said at a regular gas station (on land), he usually did not have this issue, but always seemed to have it on the water stations. vent line runs parallel/horizontal across top of tank for a few feet, then 90 bend/elbow straight up 18 inches to the bib on the fill cap assembly.

 

[xeddog]

Re: Fuel fill venting issue

My question is, since you are lifting the boat, are you sure that your lift is not tilting the boat at all? Even an inch could make a diff.

Wayne

 

[h2omansd]

Re: Fuel fill venting issue

Actually, that's a real good point I had not considered. Next time, I'll try the 5 gallon fill up method at my slip, but floating, not on the lift. Thx for the advice. sd

 

[rwidman]

Re: Fuel fill venting issue

thx Ron. I know the 7 gallon thing since I have an accurate fuel management system. So, I burn about 7.5/hour. I ran for 4 hours, knew I'd be in the 30-32 gallon range. Gas dock enabled me to put in about 24 gallons. The, went right to my house/lift, burning nothing really. Could then take 7 gallons from 2 cans and filled it up. I did this twice over a 2 - weekend period. I emailed previous owner who said he had same issue for the 6 yrs he had it and lived with the situation. Said at a regular gas station (on land), he usually did not have this issue, but always seemed to have it on the water stations. vent line runs parallel/horizontal across top of tank for a few feet, then 90 bend/elbow straight up 18 inches to the bib on the fill cap assembly.

My previous boat had the combination filler/vent and I was able to fill it at roadside stations with no problem.

I will say though, some of the pumps at roadside stations make it very difficult to "top off" a tank on a boat or on a car. Others are pretty easy.

If there's any way to route that vent line so it's uphill all the way rather than flat on top of the tank, that might help. As someone else pointed out, if the boat is not level, that could be downhill and cause a problem.

The poster who suggested a seperate vent on the hull with a vertical loop was suggesting the loop so water wouldn't enter the fuel tank via the vent and hose. Running the vent hose upward and then back down to the tank would allow water to run back out the vent, not into the tank.

I think you'll be fine with the vent you have.

 

[Captain Caveman]

Re: Fuel fill venting issue

Try pulling the gas nozzle out every once in a while when you first begin fueling. That allows more air to escape and possibly will allow you to fill more and avoid the gas spit.

 

[dingbat]

Re: Fuel fill venting issue

Where is your fill and vent entry to the fuel tank? Lots of complaints about boats that have the fill and vents on the transom end of the tank. The boat fills OK on the trailer when the boat is level, but they don't fill worth a darn when the boat is in the water with the transom lower than the bow. Fuel piles up on the end of the tank and blocks the vent fill.

I have the vent and fill in one but my fill hose is on the bow end of the tank. No problems at all.

 

[h2omansd]

Re: Fuel fill venting issue

thx folks, including the last few entries. combo vent is on right side of boat, about midship, just to the right of the outside steering station wheel. Really no way for a straight uphill shot on the vent hose, as it comes into the tank at the midway point and has to feed under the floor, across the tank a 2 feet to the right before it has anyplace to run up where the line is hidden behind a bulkhead. On the note about lifting the nozzle higher up, I do that as well, to the point where the bottom of the nozzle is practically at the top of the fill hole, with plenty of clearance all around it. The only thing I can think of, in terms of a slight improvement in the running of the horizontal part of the vent hose is that there's a notched area in the wooden rib under the fiberglass floor, just above the tank, through which the hose runs. I could possibly get a drill in there and try to notch it up just a little, as there's still another inch or so of clearance before the top of the stringer/bottom of fiberglass floor. Do u think it's worth wrestling in that small space to notch it up just one inch? Your thoughts? Or, just live with the situation?

 

[rwidman]

Re: Fuel fill venting issue

thx folks, including the last few entries. combo vent is on right side of boat, about midship, just to the right of the outside steering station wheel. Really no way for a straight uphill shot on the vent hose, as it comes into the tank at the midway point and has to feed under the floor, across the tank a 2 feet to the right before it has anyplace to run up where the line is hidden behind a bulkhead. On the note about lifting the nozzle higher up, I do that as well, to the point where the bottom of the nozzle is practically at the top of the fill hole, with plenty of clearance all around it. The only thing I can think of, in terms of a slight improvement in the running of the horizontal part of the vent hose is that there's a notched area in the wooden rib under the fiberglass floor, just above the tank, through which the hose runs. I could possibly get a drill in there and try to notch it up just a little, as there's still another inch or so of clearance before the top of the stringer/bottom of fiberglass floor. Do u think it's worth wrestling in that small space to notch it up just one inch? Your thoughts? Or, just live with the situation?

I don't think that will do much to help. I would just "live with it".

You might want to make sure there's no blockage in the vent. Run compressed air through it from the hose fitting.