oil in bilge

Terry Forshier · August 06, 2009, 09:06:27 AM

I keep getting an oil slick in by bilge. I am running my AC at the dock about 8 hours a day. the AC bleeds its tube into the bilge. I am getting an oil slick on the top. This happened a few weeks before when I changed the oil and right after that took a trip up the coast fopr a few days. After about 8 hours motoring I went below to check things and found the oil in the bilge. Stopped motor, cleaned up everything, checked everywhere, checked oil lever, nothing. Started up and motored on. A check of the motor showed the dipstick not secured. I assumed that the oil came from there. (also messy there) I cleaned up. But then a few weeks later after a few short hops I checked and again, the oil slick.
Cleaned up. Checked everything looked ok. Took boat in to yard. Had bottom painted. all well after return. Took a few day trips topped off diesel this week. Checked today had oil slick in bilge on top of water. It is a thin black film.
Ran motor for half hour.Checked for signs of diesel leak. Checked around fuel filter, nothing, around oil filter, nothing, under motor, nothing, around fuel filter on motor.
Somewhere I am leaking oil but there is no sign on the boat bottom under the motor or anywhere I can see.
Ideas appreciated.
Terry

Steve Sayian · August 06, 2009, 11:23:40 AM

Terry,

Maybe some residual oil got trapped in some small hull area between the engine and the bilge and when the AC drained, it got that oil.

Steve

Lance Jones · August 06, 2009, 12:07:49 PM

I agree as that would be my best guess. Unlike the hull exterior, the bilge is a rough finish and will collect, and hold, small amount of anything. When you wipe it up, the film will remain. If the slick is light, I'd recheck seals and monitor for either an increase or decrease in the size of the slick. Just my $.02

Stu Jackson · August 06, 2009, 12:52:53 PM

I'd get a new dipstick, the rubber at the seal eventually goes. I agree that there is tons of little nooks and crannies under there. I just used some Castrol Engine Cleaner that works very well, even better than the foamy stuff. It's like Fantastik or 409 but has a real "bite" to it and cleans up with water. I assume you've checked the seal of the oil pan all around the engine.

Ted Pounds · August 06, 2009, 04:30:48 PM

What year is you boat? When my fuel tank started leaking on my '87 the only evidence was fuel in the bilge. It wasn't until I removed the tank that I found the pin-holes in the bottom.

Bob K · August 06, 2009, 06:09:25 PM

Ted has a good point - maybe it is fuel oil? When I had a slow leak in a fuel hose by the engine, some oil would accumulate in the area under the engine over the course of a few weeks. I always thought it was engine oil, but eventually concluded it was fuel oil which picked up dirt and turned dark color as it flowed to the low spot.

Terry Forshier · August 06, 2009, 07:13:43 PM

Thanks for the tips. Tomorrow I will check again and see if any oil appears now that I ran the motor for about a half hour yesterday.
My fuel tank look new from where I can see it but will admit I did think I could see a small film on the deck floor under the sink and I did just fill it up. I thought maybe the fitting was loose and some leaked out.
It could be fuel but really does not have a smell. I do not even notice it in the cabin at all so had dismissed that.
I will keep on it though. Since the boat is in the canal behind the house I can just walk out and check it. (my wife claims I am more married to that boat then her) can you imagine that?
Terry

Ron Hill · August 06, 2009, 08:18:21 PM

Terry : As I recall you have a MK I 1988 C34.
If the dipstick was not seated ALL THE WAY, oil will come out of the tube. It will spill out on both sides of the starboard engine bed stringer. The oil on the outside of the stringer will go down to the hull thru the water heater hoses holes. The oil on the inside (under the engine) will go forward to the drain hole and then to the hull. Once oil gets on the hull under that flooring you can't get at it to really clean it up!!

Here's what I'd recommend : Take some oil diapers and stuff one under the flooring from the water heater door. You might shoot some 409 Cleaner up in there and try to clean it out before you put the diapers in there.

The bottom is that a little oil will ALWAYS be coming out of there, especially if you don't have a drippless packing gland! Sorry, you'll never get it all cleaned up !!

Terry Forshier · August 12, 2009, 02:39:07 PM

Its been about a week now with this situation and checking. I turned off the AC so that it no longer drains into the bilge. Ahhh, boat hot, but bilge dry. After a couple days i notice that in the first well in the bilge. (from the back) the one you can reach by opening the door by the water heater (1988) has started to acumulate a little oily residue. It smells faintly like oil or diesel but I really do not have a big smell in the boat. Anyhow the rags i put in there were getting damp and oiley)
My plan is to check the fuel filter on the motor and the fuel lines. (I did replace a fuel line about when this started. I had noticed it was cracking around the clamps.)(I hate to say these are probably original lines) Also I had noticed that the motor will slowly lose a little RPMs when motoring for awhile. (sort of like the cars used to when the fuel filter needed changing.) After you stop and wait awhile, eat , swim ? then start up and full rpm's again! so these are the areas I am going to check first because I DO NOT want to find i need a new fuel tank. So will look there last. (also wouldn't I see fuel dripping down through the locker in the head?)
Terry

Ron Hill · August 12, 2009, 05:47:10 PM

Terry : It sounds like you need to change BOTH fuel filters.
It also sounds like you might consider removing the fuel tank and getting it cleaned out!! A few thoughts

Terry Forshier · August 13, 2009, 09:55:17 AM

Oh No..I do not know if anyone is reading this but I did put in the papertowels in 2 locations in the floor. In the bilge and in the head sink floor. After 2 days the towels in the head were soaked with fuel. Either the filter located above it or flowing down the floor from the fuel tank. Guess i will have to start there opening up the tank and checking out the fittings or trying to see where the leak is. Always something....

Ron Hill · August 13, 2009, 06:48:19 PM

Terry : I wasn't talking about paper towels, I was talking about fuel/oil absorbant pads.
Put one under the Racor and one under the engine mounted filter, so you can isolate the leaker!

Ed Shankle · August 14, 2009, 05:55:01 AM

Terry,
Sounds very similar to the experience I had a few years ago. Your tank may be rusting through the bottom, due to water in the tank over time. It's very gradual, so you won't necessarily see obvious dripping. It just works it way down to the lowest point. If the pads you put down on the hull are soaked with fuel, I'd say that's the problem unless you find and obvious leak at one of the connections. That's what confirmed it for me.
If you take the tank out and find the platform wet with fuel, that's your final confirmation.

Ed

Ted Pounds · August 14, 2009, 09:39:14 AM

Based on my experience I'm inclined to agree with Ed...

Terry Forshier · August 14, 2009, 05:18:22 PM

would it be necessary to remove the tank to see if there are leaks?. It seemes that last time I had that pannel off I could see where the tank set on a shelf. If that is so then wouldn.t I see a leaky area or damp spot somewhere. (and yes i did put in the absorbant pads although i went to walmart and bought the kind you put on a baby bed to keep accidents from soaking the bed)
I am still hoping that this is a bad fitting or cracked fuel line/ Will start tearing into it next week.
Terry