Water in the fuel

[Jeff J]

I was called to the dock today to look at a 2017 Monterey that wouldn’t make power but start and idle okay. I automatically pulled the fuel filter and it was clogged with a pale slime and full of water so the engine mystery is solved but fuel filter only had 6 hours use. Where did all of the water come from? It is too much for condensation and the fuel cap is in good condition. Could it be coming through the fuel tank vent on the side of the boat? What happens if the diurinal gets filled with water?

 

[airshot]

Yes it could come thru the vent.... Had that issue some years back and found I needed an upward loop in the vent hose. The upward loop keeps water from running back into the tank. Also check the vent to be sure the opening is not catching spray while underway. Also be careful where you buy your fuel, I often take a sample and test it while filling my tank. Quite often the water comes from the storage tank where the supplier doesn't maintain things properly.

 

[dingbat]

By chance, do you have a self venting gas cap?

Went 10 years before the stars aligned and had water come through the vent in the cap

 

[Jeff J]

Fuel supply okay. 16 boats running on the same supply. I would be seeing more problems across the fleet if not.

Not sure on gas cap but I think it’s original to the boat (2017).

 

[airshot]

If this is a built in tank, why a vented fuel cap ? Can't say I recall a vented cap on a built in tank. That is what the thru hull vent is for....

 

[pgandw]

After about 2012?, EPA forbade new installations of freely vented gas tanks. Which is why portable tanks are the mess they are nowadays. Most new boats have the vented gas caps to reduce venting.

Reduced venting does NOT prevent condensation in the tank. But if you fill the tank on a low humidity day, your odds of keeping the air in the tank relatively dry actually improve a little bit.

Fred W

 

[Jeff J]

Condensation in a boat fuel tank isn’t any different than condensation in any other fuel tank or can. The easiest way to prevent condensation is to minimize the amount of air in the tank.

I know one of the outboards (2018 Monterey) has a vented cap. It’s all I could find to fit the threads in the filler neck. That cap is not interchangeable with the one on the inboards. The rest of the fuel system appears to be the same. 3+ years without issue.

 

[airshot]

After about 2012?, EPA forbade new installations of freely vented gas tanks. Which is why portable tanks are the mess they are nowadays. Most new boats have the vented gas caps to reduce venting.

Reduced venting does NOT prevent condensation in the tank. But if you fill the tank on a low humidity day, your odds of keeping the air in the tank relatively dry actually improve a little bit.

Fred W

Built in tanks no longer have a vent hose or an exterior vent ?? Venting thru a gas cap only could be an issue if the filler neck is filled....learn something new everyday ....

 

[Scott Danforth]

Should be a carbon canister somewhere on a post 2012. Check to make sure the hose didn't break and is laying in the bilge

 

[Grub54891]

Had a friend who had a fleet of gas powered trucks. He had his own fuel storage tank. After the tank was filled, he would fuel up first and get water in the tank. The others behind him were fine. Yup when the tank was filled it would stir up the water and he would get it. I suggested he clean the tank. By golly he had no more issues.

 

[dingbat]

If this is a built in tank, why a vented fuel cap ? Can't say I recall a vented cap on a built in tank. That is what the thru hull vent is for....

Been around since at least 1997 since mine has them on both tanks.

PERKO Inc. - Catalog - Fuel System Components - Vented Fill for 1-1/2" Hose - Straight Neck [0541]

PERKO Figure No. 0541 Vented Fill for 1-1/2" Hose - Straight Neck [0541DPGCHR, 0541G00CHR, 0541DPDCHR, 0541D00CHR, 0541DPWCHR, 0541W00CHR, 0540DPG99A, 0540DPD99A, deck fill]

www.perko.com

No vent fitting protruding through the side of the hull and no vent “loop” to worry about filling up with water.

Pretty fool proof unless the “mounting accessory” wasn’t installed and the boat is parked on a hill, fill side up for two days, and you get 5” of rain.

Own the boat for 10 years before it happened. Builder sent me the “accessory” to install. Has not happened since

 

[airshot]

Been around since at least 1997 since mine has them on both tanks.

PERKO Inc. - Catalog - Fuel System Components - Vented Fill for 1-1/2" Hose - Straight Neck [0541]

PERKO Figure No. 0541 Vented Fill for 1-1/2" Hose - Straight Neck [0541DPGCHR, 0541G00CHR, 0541DPDCHR, 0541D00CHR, 0541DPWCHR, 0541W00CHR, 0540DPG99A, 0540DPD99A, deck fill]

www.perko.com

No vent fitting protruding through the side of the hull and no vent “loop” to worry about filling up with water.

Pretty fool proof unless the “mounting accessory” wasn’t installed and the boat is parked on a hill, fill side up for two days, and you get 5” of rain.

Own the boat for 10 years before it happened. Builder sent me the “accessory” to install. Has not happened sinc

All mine have been 1992 or older, so I see I have missed so called up grades. Curious though....what keeps water out of the vented cap ?

 

[Jeff J]

All mine have been 1992 or older, so I see I have missed so called up grades. Curious though....what keeps water out of the vented cap ?

The same thing as the cap on a lawnmower. The vent is covered by the outer cap.

 

[dingbat]

All mine have been 1992 or older, so I see I have missed so called up grades. Curious though....what keeps water out of the vented cap ?

Gravity........as noted above, vents are on the underside of cap

 

[airshot]

Gravity........as noted above, vents are on the underside of cap

I must have missed that part....thanks

 

[pgandw]

Built in tanks no longer have a vent hose or an exterior vent ?? Venting thru a gas cap only could be an issue if the filler neck is filled....learn something new everyday ....

It's a separate vent hose that feeds into the gas cap. That allows you to fill the tank with vent fully open, but the vent is mostly to totally closed when the cap is closed.

Fred W

 

[airshot]

It's a separate vent hose that feeds into the gas cap. That allows you to fill the tank with vent fully open, but the vent is mostly to totally closed when the cap is closed.

Fred W

Well I have recieved my education for this week. Never noticed the vents under my lawnmower cap !!