Diesel in the bilge

[Mike H.]

We have a 94 Hunter Vision 36. We just arrived on the boat this afternoon. When loading, the boat was rocking and the bilge pumped out a little water. I pulled up the floor to see how wet it was and found about a 3 tablespoons of diesel.

I pulled apart the interior pieces to trace the leak and found nothing.

We topped off the tank three weeks ago. This problem happened once before when we topped off the tank.

Does the diesel overflow into the bilge on these boats? Has anyone else had this issue?

Thanks,

Mike

 

[Ed Schenck]

Where and how is the vent plumbed? Look to that as a source.

 

[Mike H.]

Where and how is the vent plumbed? Look to that as a source.

The vent is plumbed roght to the outboard fitting. The tubing connected to the tank is (1) 1/1/2" fill hose, (1) 1/2" vent hose and (2) 1/2" suctions to the engine. Also there is (1) inspection plate attached to the tank level mechanism. I could trace no source. of the leak. It is quite baffling, but a small amount of fuel. I'll burn a gallon off this weekend. I totally cleaned out the bilge. We'll see. Time to put the steaks on the BBQ.

 

[Steve Dion]

Mike:

I am guessing that it is a small leak at the engine, but who knows. I would suggest that you remove the access panel above and forward of the fuel tank and see if there is any signs of fuel in that area. You can also check the area under the aft bunk. The fuel line from the tank, under the berth and connects to the engine.

Be sure to check the fuel pump. When you remove the panel in the head you should be able to see most of the area where there would/should/could be a leak at the engine.

You may want to check the fill/vent hoses for a potential leak, but that is a long ways for the fuel to flow. If there is no fuel in the area around the shaft log, then it is probably at the engine.

 

[Alan]

Banjo fittings at the fuel supply pump are a traditional source for leaks. The copper washers (2 on each banjo) should be replaced each time the banjo is loosened. Wipe the area around the engine fuel filter and fuel pump with a clean paper towel to test for residue. Be careful not to overtighten the banjo bolt. They are hollow and cannot take as much torque as a solid bolt. 15 to 20 ft lbs should be fine.

 

[Mike H.]

Mike:

I am guessing that it is a small leak at the engine, but who knows. I would suggest that you remove the access panel above and forward of the fuel tank and see if there is any signs of fuel in that area. You can also check the area under the aft bunk. The fuel line from the tank, under the berth and connects to the engine.

Be sure to check the fuel pump. When you remove the panel in the head you should be able to see most of the area where there would/should/could be a leak at the engine.

You may want to check the fill/vent hoses for a potential leak, but that is a long ways for the fuel to flow. If there is no fuel in the area around the shaft log, then it is probably at the engine.

I checked all the fittings at the tank, dry. The fuel pump and filters seem dry, but engines always a little oily.

What's puzzling is the little bit of diesel that was in the bilge above the very bottom where the keel bolts are. There is a shelf there with some openings from other under floor chambers. I found some diesel sitting there. It probably sloshed up there when we were underway.

Your right, I think it came from the engine, but I can't see where. It seems to only occur when we fill the tank.

 

[Mike H.]

Banjo fittings at the fuel supply pump are a traditional source for leaks. The copper washers (2 on each banjo) should be replaced each time the banjo is loosened. Wipe the area around the engine fuel filter and fuel pump with a clean paper towel to test for residue. Be careful not to overtighten the banjo bolt. They are hollow and cannot take as much torque as a solid bolt. 15 to 20 ft lbs should be fine.

I will do that. Thanks!

 

[Dan Johnson]

Mike H...

Mike, check your hose clamps on the vent and pick-up hose fittings at the tank and at any other point along the feed from the tank to the engine and back.

Otherwise, follow Alan's recommendation on the banjoe fittings. It wasn't until I replaced all my washers that my fuel leakings stopped.

Final thought: check the tightness of the ring clamp on the engine's (assuming Yanmar) primary filter--the O-rings are vey thin and can leak if not tight.

 

[Brad Hoff]

You also may want to check the inspection plate and frame. I found my inspection plate frame had dropped several nuts into the tank. The inspection plate itself was tight but the fitting around the frame was loose. It would leak when the tank was almost full and fuel was sloshing around.

 

[Mike H.]

I've checked that. It's clean now. It only shows up when we fill the tank. So I'll bet $ .50 that it has something to do with the fill hose.

 

[Steve Dion]

Mike:

Fill hose or the vent hose (check them both)

 

[David Oliver]

Mike,

I vote with Steve. Hose from tank to vent was the problem. Hose was old and the clamp had cut through. Only leaked at full fillup. Caught it thankfully before it was pumped overboard. A smaller friend had a tight hour crouching in the lazerette!

 

[Mike H.]

The mystery continues. After we burned off a little fuel, we had no problems. Two weekends ago, we did some hard sailing for about three hours on starboard tack. Checked the bilge this weekend and pumped out about three gallons of water with about a quart of diesel.

Does starboard tack give any clues?

 

[Dan Johnson]

Hey David!

Smaller friend indeed!!! LOL!!!

 

[kloudie1]

MAN !! I know his pain.LOL. The 34's have a tough to get into hole there too.. On the diesel, check the banjo connectors on the lift pump and the secondary filter and the HP pump.. Look at the bleed screws to make sure that they aren't leaking.. .. Wipe the underside of the connector with your finger.. if it is damp with diesel, get some of the new rubber coated washers from your friendly Yanmar guy and replace the washers on the leaky fittings.

 

[robertsapp]

A quart is quite a lot of diesel. That really sounds like a lot more than you're going to get from a leaky banjo fitting or loose vent line hose clamp, unless they've just totally failed. No telling if your problem could be tank perforation or not, but here's a word of advice I posted under the thread "For those with older aluminum tanks".

Just thought I'd pass on a recent experience of mine. I pulled the 30 gallon aluminum fuel tank on our 1995 H336 to install a clean out port and do a thorough tank cleaning. Before ordering the cleanout port, I put the tank on my workbench and did a pressure test by filling it with soapy water, applying pressure for an hour with the discharge from a small shop vac, and checking for leaks. Everything seemed fine. When I cut the access hole in the tank and cleaned out the accumulated goop and crud in the bottom, I found numerous deep pits in the bottom of the tank. Many were so deep there couldn't have been more than the thickness of a sheet of paper left in the tank. It was basically a ticking time bomb, on the verge of perforating and draining my fuel to the bilge. I took it to a local welder, who charged me $200 to weld in a new bottom. So if you have an older aluminum fuel tank that you've never been in, beware!

 

[Mike H.]

It has to be the tank, hoses, or fittings. The puzzling part is the bilge has a number of "compartments" formed by the bulkheads and stringers. The bilge compartment under the engine had water, but no diesel. The diesel was in the lowest part of the bilge in the center of the boat.

Apparently I'll have to take up the floors, aft berth top and the back wall to trace the trail of the diesel. It will most likely take me to the tank. Nothing on the top of the tank is leaking. I pray to Buddah it's just a hose and/or clamp.

Robert; Why would the aluminum deteriorate in a diesel tank? I understand the chemistry in a holding tank, I replaced that two years ago.

 

[robertsapp]

I don't really know for sure. There's a chance it could be electrolysis, because I have an electric level sender in the tank, the tank is bonded, and diesel fuel is probably a conductor (electrolyte). Or maybe the grimy biological gunk I found stuck to the bottom of the tank was emitting something that attacked the metal. All I know is that that tank looked fine from the outside, but it was OH MY GOD on the inside, with numerous deep pits. It was probably only months away from perforating.

 

[Mike H.]

I found the leak. The leak happens where the 1 1/2" fill hose connects to the aluminum tank.

The tank was installed before the upper parts of the boat where bonded to the hull. The tank is covered with a piece of plywood that is the floor of the port side cockpit lazarette. A slot was cut through the plywood to allow space for the fill hose. However, The slot was not long enough and pushes down on the fill hose and aluminum spout for the tank. The worker probably had to stand on the plywood to hold it down while other workers screwed the piece in place, then they glassed it in. Additionally, it would be impossible to loosen the hose clamps as the heads of the screws are looking at the aft stateroom bulkhead less than 1" away.

What I'll have to do is use a flooring trimmer or rotozip or saber saw to elongate the slot to allow access to the aluminum fill spout, use a dremel tool to cut the hose clamps, then install a new fill hose and clamps.

Until I do that, I have placed absorbant pads in strategic locations to absorb any leaking fuel that might escape until I get to this fun chore.

I am happy to report that I can fit all of my 230 pounds inside the lazarette!