gas spilling from tanks while sailing heeled

[Trav White]

Finally took my Mac '02X out on Monday in some rough water and stiff winds with an experienced friend of mine. Heeling out to 15 degrees sure was nerve-racking, but he convinced me that the boat was not going to capsize. We even gusted a couple of times out to 25, definitely not comfortable. But, while doing this, the kids complained of smelling gas fumes. I have 2 12-gallon tanks that I had just filled on Saturday. It appears that gas was spilling out of the vent on the top. Is this common while heeled? Should I close the vents each time I sail? Does anyone have experience with this?

[Night Sailor]

Yes, especially in hot weather, full tanks will give off fumes when the boat is heeled and the tank vents are open. Close them because if you need to quickly start the engine in an emergency you can, and run for a minute or two, giving you time to open the vent on the correct tank.

[zuma hans 1]

Your tanks are too full. Unless you are immediately about to head out on a long cruise, and will need every possible drop of gas in the near future, there is no reason to have your tanks that full.

Leaking gas is unsafe. It is bad for the environment and the fumes are hazardous. There is a danger of fire.

My 6.6 gallon tanks can accomodate 7 gallons or more, but 6.6 is the most that -should- be loaded at risk of leaks.

[delevi]

I don't think you should have the vents open at all while operating the boat. Only vent them when at the dock or on the trailer. My tanks don't have vents at all. The dealer told me that this is how they're made now. I crack open the caps when the boat is on the trailer to let the fumes out, espcially when it's hot. When I am using the boat, the caps are cranked down tight. A few times, I had gas seep out of the valve when unplugging the intake hose to change tanks, probably due to pressure. Had to clean up in a hurry.

PS. Don't worry about heeling 15-25 degrees. This boat can be knocked down 90 degrees and will recover fully. Not a pleasant experience but comforting to know. I frequently sail in high winds, and actually look forward to only heeling 15-25. If I can keep it under 30, I'm doing well.

Fair Winds
Leon

[Beam's Reach]

Delevi wrote:

I don't think you should have the vents open at all while operating the boat. Only vent them when at the dock or on the trailer. My tanks don't have vents at all. The dealer told me that this is how they're made now.

I always thought the vents had to be open slightly to allow the gas to flow...sort of like punching the second hole in the top of the juice can.

[Chip Hindes]

I always thought the vents had to be open slightly to allow the gas to flow...sort of like punching the second hole in the top of the juice can.

There's no way a tank which is properly sealed in the first place will allow the motor to function without a makeup air vent of some type.

I have on more than one occasion stalled out the motor by forgetting to crack the cap vents. The only variable is how much gas is in the tank. The less gas, the longer it takes for the induced vacuum to starve the carburetors, and with less gas and a well sealed tank, the induced vacuum can actually collapse the tank inward as if it's going to implode. BTDT.

When it happens, it's just like running out of gas and my motor will not restart until the tank is vented and the fuel bulb pumped up to refill the carburetors. When you open the vent you can easily hear the air rushing in. Fortunately or unfortunately, depending on how you look at it, I've done it enough times that I usually know immediately what has happened, and sometimes I can detect it in time to get the vent open before the motor stalls.

The dealer who states some particular tank is not vented is mistaken. Tanks which lack the conventional cap vents are simply vented in a different, less visible fashion. Some of the newer, more expensive tanks have automatic, one way vents which allow air to enter but no fuel to escape.

[DLT]

Yeah, gas will leak out the vent when heeled over. Its common and easy to fix. Just close the vents. You really only need the vent open on the tank the motor is currently using. I just try to make it part of the switch over process (switch tank, open vent, close other vent).

[Jeff Drumm]

There's no way a tank which is properly sealed in the first place will allow the motor to function without a makeup air vent of some type.

My Honda BF50 will actually collapse the tank if the vent's not open. I guess your motor doesn't suck as much as mine

[Gemini]

Yes, I have experienced both. First I was smelling gas and asked the dealer about it. He said the vents were too opened but they need to be opened some or the tanks will collapse due to heat. He never mentioned the engine.

Then a few weeks later I was at the gas station filling up both tanks. I had messed with adjusting the valves, about half open, turned a few times but snug.

Then took the boat out and after about 10 min. or so of motoring the engine cut off. I pulled it up and there was some weeds around the prop, I thought it was that, cleaned it and the motor started (I assume the pressure had released while the engine wasnt running). I didn't have that problem the rest of the day but, I mostly sailed after that.

The next day that came to me: that I had adjusted the valves and that is what caused the motor to cut off. I hadnt had the motor cut off ever before, brand new engine, etc

I keep the vents pretty opened now but not all the way. My theory for now is if they are opened enough for slight pressure to allow air flow then with the motor running or heat building up, that should allow the air to flow. But not opened enough for the gas to just flow out when heeled.

I didn't have an issue with gas this last time out and I was at times at least 25 degree if not more with gusts. No motor cutting out. I think it is both, not opened all the way so it won't just spill out but will allow air to flow under some pressure.

I will let you know if I find this to not be the case since I have only had my boat for a month and a half.

I just love the boat. My son (17) love it as well, at least as much as I do. Best thing we ever bought. Big hit with the whole family, and sailing is just so relaxing!

[Don T]

Hello,
Also, be aware that the gas caps usually have a thin gasket that can tear or crack leting a small amount of fuel leak out when heeled over.

[delevi]

I guess I have the newer version of the tanks which self vent without caps. They were about $50 each (6 gal tanks) I have four. I didn't know that others needed vent caps to be open. The self venting ones are well worth the money, in my opionin. No spills.

Leon

[Mark Karagianis]

Gas tanks - another one of those annoying things that you have to remember about. If you forget to open the vents, your tanks can swell up and push up the seats to a 30 degree angle, and look like they are about to explode!

And yes, if you don't open the vents enough, the running motor (especially at WOT) will collapse the tank when near empty to a degree that you can't believe that it can bounce back from (mine did). And you wouldn't even know it- all of the sudden the engine just can't suck any harder and quits.

The Mac has other annoying things to remember about too (like ballast valves, centerboards, rudder bolts, and relieving pressure on the trailer winch before launch), but we love ours and it's versatility.

Mark

[Trav White]

Thanks for the help. It is my understanding that the tanks should be vented when connected to the motor. I did realize that my starboard tank is a new Tempo 12 gallon and did not leak. My port tank is older, I'll have to check the cap, it is probably 4 yrs old, like the boat. Just need to remember to close vents when sailing.

[craiglaforce]

I leave my vents open all of the time, unless they are being transported in a vehicle. nothing leaks out, but do not fill the tank above the fill line. SHould be a decent air space left for expansion. For sure they have to be open when running the motor.

I guess there are new tanks that are self venting. I guess I want the control.

[Idle Time]

I could be wrong...but isnt 15 deg about normal for the Mac when under sail? It always seemed to us that it kinda goes to 15 pretty fast but then it settles in there unless the wind picks up alot. I've had it to 45 ....Jim went below to clean up what I had just put all over the floor on a steady 35 deg....just as he was coming up and was eye level with the level it hit 45....I held it there as long as I could then the gust passed and we dropped back to about 30. .....fun ....fun....fun....but 15 seems like a lot when we first go out.....go figure.