Fuel Breather Position Stinks

[SunnyCoastrunner]

The position of my fuel breathers are on the transom towards the centre of my side of the boat when standing in back corner fishing and when the ocean becomes choppy the fuel sloshes around in the tank causing alot of fumes to come from the breather where im standing.The Hardtop on the boat causes turbulence and sometimes you can smell it in forward cabin if breeze is strong enough 15kts+ Sometimes this is unbearable causing me to be sick. The easiest solution to this is to swap sides but my mate doesn't catch any fish on that side of boat. I could put a couple of valves on there but that would be a pain does anyone have any ideas to solve this problem!

[death_ship]

buy an ETEC, they dont use any fuel

[robothefisho]

Apart from moving the breathers, I'm thinking about the only way is to get some baffles put in the fuel tank to stop sloshing. No idea if it'd work though.

[marto78]

You could try lengthening the breather hoses.

[Daisy Burnett]

buy an ETEC, they dont use any fuel

Now thats funny.

[oldboot]

Think about moving the breather/s onto the side of the boat below the gunwal.

being on the square stern will place them in a turbulent area..the bow will always be into the wind..so the stern will have this backdraft thing happening like the exhaust commong in the back window of a station waggon.

if the breether is well up the side of the boat the wind should carry the fumes away.

BUT

I am wondering why you are getting so many fumes in the first place.

the breethers should be as high as possiblecheck the routing of bothe your breethers and fillers.

the breether should have no low points or high points between the nipple on the tank and the outlet...continuoulsy going up.

If there is a low point...if you overfill it can hold fuel..and it can tend to splutter fuel instead of just air & fumes up the breether resulting in excess fumes.

cheers

[cormorant]

I'm the opposite of oldboot but different boats need different set ups . If it is a recent boat or under warranty get the dealer to sort it and have a look at how it is done on new boats.

I am not a fan of why tehy put it on the transom. Side is better in my mind but on smallerboats it may take water?

I'd be checking if that is really where it is coming from for a start. Check there is no holes and no fuel leaks,weeps at tank , hoses or motor,

Put a couple of loops in the breather hose 6 inches under the gunwale and put in the loop some really light oil. Air goes past but loop of oil will stop most fume and stop a lot of tank condensation.

On the plus side you are obviously buying good fuel wih lots of araomatics and light volatiles in it. The stuff I have got has no smell and barely catches on fire.

[Boat Hog]

On the plus side you are obviously buying good fuel wih lots of araomatics and light volatiles in it. The stuff I have got has no smell and barely catches on fire.

Not everyone was able to stock pile fuel when it was 60c a litre Cormorant!

You could try an in line breather filter Whitworths have one for $59.95. They write it up as an "activated carbon filter will keep your boat smelling clean and pleasant. Fits inline in your breather hose. Connections suitable for 19mm or 20mm breather tube. This filter is clear at one end allowing you to see if the filter needs to be replaced. Mounting brackets included."

Link; https://www.whitworths.com.au/main_i...AbsolutePage=5

[SunnyCoastrunner]

Thanks but tank has baffles

[Fed]

That's a dunny filter Boat Hog and would probably clog up in no time.

I think you have a leak somewhere SunnyCoastrunner.

[oldboot]

UM not Keen on the filling the loop with oil.....if I did that on mine, it would get spewed out every time I filled the tank...and there is a posibilty that it could get sucked into the tank contaminating the fuel.

Some systems, people report finding a loop helpfull....but I stand by my assertion that the rest of the breather path should be uphill

Remember that one of the rolls of the breather is a filling air relief, to let the air out of the tank as the fuel enters.

one other thing to check is that the breather tube is of adequate size.....mine had a way too small tube ( 8mm fuel hose) on it when I got it and on filling the breather would splutter wet fuel.

The aim is to keep the air speed reasonably low in the breather tube..it should be something like 12-16mm ID all the way to the tank......the volume of air that needs to come in and out of the tube remains the same..there is very little you can do about that.

If however the tube is too small, as fuel gets up into the lower part of the tube, the air velocity is such that it can be propelled all the way up the tube and out the vent...particularly on filling.

A larger tube will allow the air to pass up and the fuel to flow back to the tank, double the ID of the breather and you reduce the air velocity by much more than half.

If your breather is too small, and there is a loop....on filling anything in the loop will be ejected
and there is a real good chance that a quantity of liquid fuel will remain in the loop.

After filling the air velocity in the breather remains quite low so this fuel may never get sucked back into the tank or ejected in volume, but with heat and rocking, it may provide a constant flow of fumes out the breather.

Like most thing on boats fuel tank plumbing is a pretty hit and miss affair with what you find.......but start looking at automotive fuel tanks and it is all pretty consistent...big filing breathers and all uphill...just dont look at holden and ford fuel tanks...the fillers on those work poorly at the best of times.

cheers

[cormorant]

The other way is to have the smaller breather hose from the tank go into a larger barb and 15cm of larger hose 25mm and then back to the small hose out to the breather all mounted vertical. That way any fuel that goes up ends up in the 25mm larger hose and them dribbles back down into teh tank. If it is a fume issue the fume will still go out and smell as ther eis nothing stopping it.

With the loop the oil doesnt reallty move into the tank and would do no harm. You need enough height and obviously the gunnel height and large enough tube.

Put your mouth over the breather and see if it blows bubbles into the tank with the boat on the same angle as it would be on the water. If it does a fair bet is the breather is in the wrong spot

Can you access the tank and see the hoses connected? Wouldn't be the first one to be connected wrong or have the hose lying in the blige below tank level.. Hose from top of tank at front?

Honestly a breather should do bugger all on filling as all the air and fume in the tank comes out the filler as it is larger and has less resistance. Only in the last "top of the tank" should a breather have fume pushed out.

Boat tanks are pretty poorly designed overall with no expansion tank area on top and breather points in the wrong spots. Car tanks these days are sealed affairs that accept pressure to a point and have a vacume valve to let air in as fuel is used.

There are vapour fume and water traps avaliable for bigger boats at a huge price.



Boat hog - nothing wrong with mil spec fuel from 1945 - if you can smell it it will fire! 60c a l memories

[Boat Hog]

That's a dunny filter Boat Hog and would probably clog up in no time.

Ahh yes. That's teach me to post so early in the morning!

[oldboot]

Sorry to be argumentative but.

If you look at most marine ( and automotive for that matter) fillers that do not go directly into the tank, the fill hose is not much larger than the bouzer nozzle,,typicall 30 to 35mm.
The flow out of the bouser nozzle is far from laminar ( steady solid stream) the fuel spreads out and partly occupies the whole filler, if there is not sufficient flow in the fill breather there may be a spluttering or back splash in the filler, at worst this may cause fuel to come out of the filler at best it causes nucance tripping of the pump cut off.

This is why most modern, well designed cars have quite a large fill breather like 12mmm pluss , 16mm half the fill diameter is not unusual.

Look at most of the availale marine fuel breather fittings and they are 13mm hoseID..there is a good reason for that.

BUT the marine industry being the marine industry......cheap scates go for a small 3/8 or 8mm breather hose, because it can be baught as standard fuel hose and at a fraction of the cost of harder to get 1/2" or 13mm fuel rated hose.

As for putting extra joins and adaptors in any fuel line, apart from being expensive once you buy the adaptors and hose clamps......extra joins in a fuel line are never a good idea.

But the matter for the original poster remains.

Ya need to have a good look at how your tank is plumbed and how the hoses are run.....

I assert that the breather hose should not have any low points, especially it should not go below the top of the tank at any time...........further that the whole path of the breather should allow any fuel that gets into the breather to flow unrestricted back into the tank at any state of boat trim...and it should be large in diameter.

Now consider this.
If you have a centre mounted fuel tank....the best place to put it...the top of the tank will come very close to the deck level....if the breather is routed to the stern under the deck......even with the best effort.......it can not help but have a low point at the rear when the boat is comming onto the plane.....at exactly the time when the fuel is surging about in the tank.

If you have a high filler....when the tank is full....there will be fuel in the lower part breather hose..lots of it.

Then....at rest when you are fishing out the back the breather line has probaly got a low point in it too..and every time the bow rises with the chop..that fuel sitting in the breather is thrust rearward.

In fact most of the time, any power boat is sitting stern down with the deck and any underdeck breather pipe sloped to the rear.

If you take the breather directly to the side and up to gunwal level...there may be a very much shorter flatsih section of breather line and the majority will be very upright.

I hope this helps.

cheers

[SunnyCoastrunner]

Thanks everyone,I will try a loop in breather hose and let ya's know if it works.I don't have any leaks in tank or hoses fittings etc and I have never had actual fuel coming out of breather just lots of fumes is the problem