tank vent

[code blue]

has anyone experienced the phenomenon of sucking sea water through the tank vent. Routinely fish in 4-8 foot seas here and the tank vent is continually under water. Have had to empty separs endlessly on trips this year. Tried everything poished the tank 3 times. Finally I cut the vent hose and added a three way valve to direct intake in the boat while running and can flip the lever to vent out when fueling. 4 trips now and not a single drop of water. The hose was as it was advertised per specs. I theorize that the injector pumps on the D4 common rail engines are extremely powerful. Any thoughts from others?

[CClassic28]

Same issues here when running in the slop. Good idea with the 3 way valves. How do you access them to make the switch?

I thought about siliconing SS clam shells to the hull to cover the vents but really like the way they will look.


Chris

[TwinFin]

Yes!!!

I thought I was the only one who thought this was happening. I am convinced that the water I have seen in my racors comes in through the fuel tank vent. I see more of it on rough trips, typically when I have weather on my port bow on the way home. I have disconnected the vent line after rough trips and I get a bit of water out of the hose if I tap the end against something - but I have not yet proven that a significant amount enters this way. Our factory runs the hose with a loop that raises above the vent level in an attempt to inhibit water entering but I don't think this is effective enough when weather is keeping the vent wet and fuel consumption is causing a vacuum to pull air in from the vent. I made the trap shown here to catch the water (and prove to myself that's where it's coming from) but I have not yet installed it. The trap consists of a diesel compatible plastic bottle fastened to a mounting bracket via velcro. The bottle has two nipples on the top and it is positioned in line with the vent. It is to be mounted inboard of the vent location, behind the wall and accessible via the service hatch near our tackle center. Any water that enters will be caught in the trap rather than enter my tank and the bottle can be easily removed and emptied. Only drawback is this will mean opening the service hatch each time I refuel to see the "burp".

I think I also like the alternate idea of a valve that can be switched between inboard and outboard vents.

Questions.

Can you tell us a little about the polishing process? Is the fuel simply filtered or is the tank actually thouroughly cleaned? How is it done? How much does it cost? And is it effective at removing sludge that may be on the tank bottom as a result of water intrusion? I'm specifically asking about effectiveness because I know our tanks are baffled. I was thinking I might have my tank polished before I start using the trap - but I need to be educated on "tank polishing".

[code blue]

tank vent

thanks for the reply. We all thought we were crazy but you cannot deny water in the fuel. I have tasted it several times and it was salty.
The process is simple and took 15 minutes. Just access the vent hose through the access plate after lifting the engine hatch/floor. simply cut the hose and add an additional piece of hose for the in hull intake portion and attach the 3 way valve and using the lever vent outside when fueling and inside when running.
Fuel polishing best done by professional, look in the yellow pages and make sure it is a high presuure system so they actually power wash the inside of the tank while sucking and filtering fuel. With these two steps you should be good to go. To date not one drop of water since performing this simple procedure.

[TwinFin]

Thanks. - I'm curious about the Y valve you selected. I have not found one yet that I like. Do you recall what you used? (vendor, part #)


Steve

[code blue]

tank vent

Will see if I can read off the valve. Generic 3 way brass 3/4" lever valve purchased at plumbing store.

[stanley111]

tank vent

I just wonder if water in the fuel from the vent and the problems cummins has had with there fuel injectors are
related ? each time i have had injector problems have been after or during rough sea conditions and during the winter in cold water . interesting thought

[TwinFin]

Tank Vent - update

Thought I should update this thread.

Last season I moved my tank vent to a location under the gunnel - just above the water spickets. I know the whole question of water entering via the tank vent is controversial - but I have to say that I am absolutely convinced that in my case, on rough days with lots of weather off my port bow, I was sucking water in. I use to find it in my racors after rough trips. Weather is generally from our northwest and we get it worst on trips home from Mexican waters when the afternoon winds are up. The vent is constantly bathed by water under those conditions.

Any way, since I relocated my tank vent under the gunnel, I have not seen a drop of water in my racors. I keep a plastic bottle with a small hole the size of the vent o.d. cut out of the bottle side wall, over the vent all the time. It fits nicely up there and when I fuel up I just lay on the deck and listen under the gunnel. Any burping is caught by the bottle.

My advice: leave your vent alone if you are not seeing any water in your separators but consider this possible entry route if you are seeing water after rough trips. Relocating the vent is simpler than the trap or a Tee - other ideas I considered.

[Patriot]

Wouldn't the easiest fix be to just add a stainless clam shell (angled to protect from forward water entry) over the exisiting vent opening, lots of boats have just those with no issues and they really aren't that ugly IMO.

I don't understand the theory behind the three way valve. If you get water ingestion inside the exterior vent, wouldn't the vent and hose to the 3 way valve just be full of water when you changed the valve position to fuel thus dumping that water into the tank anyway? I would expect droplets at the very least.....

[code blue]

vent

I have not had a drop of water since switching. I access through side plate in engine compartment. With the bend in the line I put the 3 way at the lowest point. The engines suck air from a small piece of hose vented in the compartment where the hose sits. When I fuel up I switch to outside vent and a few drops of salt water is pushed out as the fuel pushes air out of the tank. No water gets in this way only out. Our waters here are usually 4-6 foot on normal 20 knot trade wind days and those vents are continually under water here. One caution however, the hose goes through a pvc ring whivh can kink the vent hose. You must reach up inside to check this. If you have a problem filling with burping fuel this is probably your problem. rob