Okay - I have a mystery on my hands (well a mystery to me anyway). A couple of weeks ago I topped-off our fuel tank for the first time. I had my buddy and two boys down below in different areas looking for any obvious leaks as I did so - just in case. No issues.
When we got back to the dock after running the motor for maybe 2 hours total one of the boys asked why it smelled like paint below. Uh-oh. I went down and sure enough there was a strong smell of diesel. I checked the engine bilge and there was just a bit of water in it. Then I checked the main bilge and there was maybe a gallon of diesel in it - mixed with some water. Damn. I pumped it out with a manual pump then our mini shopvac. We stayed at our buddy's house for the evening then came back to the boat the next day. No more leak.
Our assumption at that point was that I'd just over-filled the tank and it had a leak somewhere in the filler hose that leaked when we heeled. No big deal - I'd just try to track it down before filling up again.
This weekend we had exactly the same issue after about 2 hours of motoring. So it doesn't appear to be an overfill issue. Here's my troubleshooting thus far:
I checked the engine compartment. The bilge only had a bit of clear water in it (I assume from the stuffing box). There was no diesel and neither of the filters or hoses showed any sign of leakage.
I then pulled the cover in the aft cabin to have a look at the tank and generator. There were signs of slight leakage on the tank - but the odor wasn't all that strong and I didn't see anything that would indicated a gallon or more of the stuff spilling over the course of a few hours...
The fuel filter between the tank and the generator seemed to be dry as well.
So a few things are throwing me here:
1. This problem didn't show up until I'd topped off the tank. The test sail during the survey had us motoring the exact same time and distance. No issues that we saw. How could we still be having overflow if it's a filler hose issue?
2. I'm not exactly sure how each compartment feeds the main bilge. But how could the tank compartment and the engine bilge not show pools of diesel - with it only ending up in the main bilge? I assume that it's the tank leaking in the aft compartment and moving through a drain hole directly to the main bilge - bypassing the engine bilge?
3. There just didn't seem to be enough wetness or smell in the tank compartment to indicate that much leakage. Where else could it come from?
4. The motor is running fine - not missing or sounding starved in any way.
Any advice on where to start?
Finally, what is this thing atop the tank? At first I thought it was a gauge (and maybe it is) - but I can't make sense of it.