Fueling our boat/re-routing vent hoses/fall project

[redbeard1]

Hello all,

as our season ends, I am thinking about one of our planned fall projects - rerouting the fuel vent hose.

It takes over a minute to add one gallon to our tank. If we exceed this rate, fuel begins to overflow. We have traced our problem to the fuel vent line (when I remove the fuel gauge on the tank to allow air to enter the tank, we can fill the tank at a normal rate).

The vent/hull fitting is clean. But there is a 2-3 inch vertical drop in the hose after the hose leaves our tank (see attachment 1). This drop in hose is consistently filling with fuel (maybe when the boat pitches). Once the drop in the hose is filled, we again have a problem with the rate of fuel fill.

We think we have a solution but I would appreciate a sanity check.

Please see attachment 2 & 3. We are planning to extend the vent hose forward, loop it 6-9 inches up into the aft end of the engine compartment, then loop it back down to enter its original exit hole in the starboard lazarette. We also plan to add an Atwood anti-surge fitting at point A to minimize the chance of any fuel entering the downward part of the tube.

Can anyone see an obvious problem with this arrangement? Any suggestions?

https://www.amazon.com/Attwood-Fuel-Vent-Surge-Protector/dp/B0000AZ7PE?SubscriptionId=AKIAJ7T5BOVUVRD2EFYQ&tag=camelhomerecent-20&linkCode=xm2&camp=2025&creative=165953&creativeASIN=B0000AZ7PE

 

[jarnold67]

Maybe I'm missing something...

On our boat, both the fill and vent to the (diesel) tank are located at the top of the tank. The vent line has a relatively straight run up to the vent hole (which is located on the transom, below the fill opening). I'm not quite sure how you are getting fuel in the vent line, but could you either modify the vent line run such that the initial portion is vertical? Or possibly shorten the length of the vent line to remove the drop? It seems to me that adding in a vent loop is only making your situation more difficult. Other point to consider is to look and see if the vent line is clear and unobstructed.

Best of luck,
John

 

[Christian Williams]

I see no problem removing the droop from the vent hose so it doesn't collect fuel. Hold it up with a string?

Air definitely needs to come out as the fuel is going in.

(The only way to fuel my boat to full 55-gallon capacity is to pump fuel slowly in (no foaming) until it comes out the air vent.

I don't know about anti-surge valves, but the reviews of the product you cited are not very encouraging.
I

 

[redbeard1]

Thanks for reply John,

I should have mentioned our boat is a 1993 34-200.

The fill and vent hoses attach to a recessed area on the side of the tank (there are a few posts on this website explaining why this was done, short answer is bigger advertised tank, more space in aft cabin) see attached picture 3. The vent hose then goes a little forward and begins to curve to starboard but dips 2-3 inches before entering the port side of the starboard lazarette (see picture 4). The vent hose then rises until it is near the inside part of starboard gunwale. It then heads aft and exits the boat through a fitting on the transom (see picture 1). From what we can tell, the problem is mostly due to the initial dip in the hose.

In order to have the vent hose rise continually from the tank, we would need to drill a new higher hole in the port side of the starboard lazarette (and that would still leave us with about two feet of relatively no-rise hose). Plus we're not sure if the area where we would drill the new hole is free on the other side (i think we might run into the water heater).

Our solution (see picture 2) is to extend the hose forward as it leaves the tank (section A), ensuring it only rises, then we run the hose vertical for 9 inches in the aft part of our engine compartment (section B). While the vent hose will dip as it returns to the port side of the starboard lazarette, we are hoping the almost 10 inches of vertical rise (plus the atwood fitting) will ensure no fuel ever makes it to the new dip in the hose.

I agree this may make things worse if fuel makes it to the new dip.

The fitting and hose are clean. Does anyone with this set-up take so long to fill tank?

 

[supersailor]

Check the screen on the vent thru hull on the stern. I had this problem but worse and it turned out to be the screen on the vent fitting on the stern was totally plugged. The temporary solution was to use s phillips head screwdriver to punch out the screen then to replace all the vent thru hulls. Haven't had a problem since.

 

[Loren Beach]

Probably 'thinking outside the box' a bit too much, and 'different boat and not really too applicable'....

But when I replaced our fuel tank a number of years ago and also replaced all (!) of the hoses, into and out of.......
I decided to go after a long-standing frustration with fuel emerging out of the vent on the top of the transom with a full tank and also when pounding into a head sea after a fill up.
Problem was that the top of the tank was not enough lower than the vent, and that the vent was after a looooooong hose run, from settee all the way to transom, with lots of loops in the hose run. EY had fastened it up under the side deck every couple feet or so.

I glassed in the hole in the stern. A new ss vent was installed near the top of an inside surface cockpit combing right aft of the point where it meets the cabin back. I routed the hose inside of there up a couple of inches and thence down and forward to the tank, with a slight down-hill slant all the way to the tank. It is still (sigh...) just a few inches above the deck fill level, so that I have to slow the fuel flow when adding from a commercial pump nozzle, or a tiny bit of fuel emerges from the vent. But it's a LOT easier to put a paper towel on the bridge deck than to try to catch a lot more fuel on the back of the hull.

Anyhow, the higher inboard location has 99% solved the problem.

We used to have to tape a piece of towing under that old transom vent when refueling.