Slick from raw water exhaust

zAr · #1 (**permalink**) 08-25-2009

Can someone give a checklist of things to check when a slick suddenly appears from the raw water exhaust after motoring for less than an hour? This is a Volvo Penta 2002 (2 cylinder, 4 stroke) engine on a 1986 CS30 boat. The boat is recently bought, recently checked by a diesel mechanic and given the ok, I believe he replaced the gear reduction coolant hose, added oil, gave the whole thing an inspection then gave it the thumbs up, and I've only motored it probably 3 hours top.

I'm a newbie, btw.

Thanks in advance for your help.

imagine2frolic · #2 (**permalink**) 08-25-2009

I would ask the man who gave the thumbs up.........i2f

jackdale · #3 (**permalink**) 08-25-2009

Was the oil overfilled?
How many hours on the engine?
Has it been rebuilt?
How is the compression?
Does it have loose rings?

flatracker · #4 (**permalink**) 08-26-2009

How much of a slick. How many hours on the engine. Had it been sitting a long time without running. A slick could be either engine oil, or unburned diesel. Or if you have a trans. oil cooler could be trans. oil.

zAr · #5 (**permalink**) 08-26-2009

Well, before I bought it, it had been sitting on the hard for 7 years, though the owner claims it was professionally maintained - oil changed yearly, engine run hot for several hours, everything waxed, then properly winterized. The owner, an attorney, refused to give me a guesstimate as to the number of hours on the engine, so I just used the 200-300 hrs per year rule.

The slick is light, a thin rainbow coloured surface discolouration. The engine hasn't been rebuilt and is definitely one of the nicest engines I've looked at, very clean, well maintained, hardly any rust, no leaks or drips, the engine pan is almost spotless.

I'll have to get back to you guys tonight regarding oil levels and O rings. I also plan to run the engine again and see what happens. It was toward the end of my motoring around that the slick appeared. I think I would have noticed a slick at the start of my trip.

hellosailor · #6 (**permalink**) 08-26-2009

Could just be unburned fuel, from an injector or timing problem.

The transmission cooler is the easiest thing to eliminate. I'd also ask the diesel mechanic to come back and see what he missed. If the injectors have never been serviced, after all that time in the yard they might very well need a rebuild. Did he pull them and check them?

timebandit · #7 (**permalink**) 08-26-2009

Rule #1??

No?

Then--

I would think that checking fluid levels would eleminate the trans and engine and that would leave fuel.

hellosailor · #8 (**permalink**) 08-27-2009

So with an air block some fuel could get blown past the cylinders into the exhaust, and then blow out unburned after startup, causing a small slick on starting?

But the OP said the slick only started after motoring for less than an hour indicating it was well after the engine had started up, heated up, and gone into "steady state" operation?

I wonder if we can hot-rod a Chevy Volt powertrain into a sailboat...

zAr · #9 (**permalink**) 08-27-2009

I've now checked and I think there might be too much oil in what I think is the reverse gear housing. The engine has two dipsticks, one in the middle section on the port side, the other in the starboard aft section of the engine, in what looks like the transmission area. In the latter the oil reading is higher than the flat section of the dipstick by about half an inch. Yet, this couldn't be the cause, could it, if the slick is appearing towards the end of an hour of motoring and not at startup?

Never having checked the oil before this (dumb of me, I know), I don't know if the oil level there is increasing, but it's clean yellow translucent oil - as I would expect if the oil has been recently changed, so I'm inclined to think it's not "growing oil" as I think then it would be dirty, milky, watery, or whatnot.

I didn't check the O-rings as, from what I can tell, I'd have to take things apart for that. I'm not quite ready to do that yet.

Cardiacpaul, thanks for that insight re: tiny amounts creating quite a slick. Actually, the sight of slick, any slick, did alarm me. This kind of slick is normal with boat engines?

Re: air block shutdown, the engine actually wasn't shut down when I noticed the slick, I like to leave the engine running in neutral until I have the boat securely tied up. It was as I was tying up and before shutdown that I noticed it.

From what I'm learning this unburnt fuel getting into the exhaust business seems like the most likely source of the slick. I say this because, to my (inexperienced) mind, that's the one place where oil/fuel and water mix, by design, as the cooling water goes through the engine. Everywhere else the oil and water are kept separate and mix only if there's damage or corrosion.

So that seems like the most logical place to start ruling things out. I guess checking the injectors and timing is my next step. Gonna research how to do that.