BLACK BLACK oil

Breezer · Outlaw Joined: 17 Jan 2003 Posts: 246 City: Austin

I change my oil every 50 hours, sometimes even in 40 hours. After about 20 hours of an oil change my oil is black as death on the dip stick when I check the oil. Why? Is this normal? What could be any problems? The boat run pretty good. Indmar 310hp inboard.

Breezer · Outlaw Joined: 17 Jan 2003 Posts: 246 City: Austin

By the way, I use 15W40 oil.

MrBlean · Posted: Sep 11, 2003 6:12 am Post subject:

Black oil is full of carbon deposits. These derive from combustion. It could be that your piston rings aren't sealing as effectively as they might (rings or bores worn) and during the firing sroke, a small part of your exhaust gas leaks past the rings and deposits carbon into the oil. Another reason could be that the engine is running too rich creating lots of carbon deposits in the first instance and exacerbating the situation.

You could try using flushing oil to the engine thouroughly then refill with fresh oil and see how long it takes to get dirty from a clean start. It may well be that a lot of the carbon is simply washed off the insides of the engine each time you change the oil.

P.S. How old and how many hours has the motor?

Leggester · Posted: Sep 11, 2003 7:27 am Post subject:

Also, I'm assuming you change the filter too? I'd suspect carbon as Mr Blean suggested. You can always try some Slick50 and see if it helps the rings.

BTW, you really don't need multi weight oil in a boat. Unless you run in cold weather. e.g. 20degrees and lower.

Breezer · Outlaw Joined: 17 Jan 2003 Posts: 246 City: Austin

The boat has 290ish hours.

MrBlean · Posted: Sep 11, 2003 8:25 am Post subject: Low hours

Wow, given the low hours I'd be surprised if it was a rings/bore wear phenomenon. At 45 hours since my last oil change the oil in my 300 hour LT1 equipped MC is only just beginning to darken. In contrast, the oil in my 160,000 mile Audi turbo-diesel is black within 3,000 miles of a change. That's because diesels create more soot in the first place and the compression is much higher so it's easier for exhaust gases to squeeze past the rings. Ands at that mileage, the bores/rings are hardly in pristine condition. But at 290 hours!!!!!

Have you owned the boat from new and can verify the hours? What about its service history, has it been well maintained? I have read several horror stories on this site regarding engines blowing up at 400-500 hrs.

Always difficult to bottom these out but many relate back to poor servicing & maintenance like failing to change the impeller which fails causing and engine overheat. Not been there yourself, I trust?

Do you get any blue smoke out of the exhaust on start-up and subsequent running?

Breezer · Outlaw Joined: 17 Jan 2003 Posts: 246 City: Austin

I bought it with 170 hours and have taken care of it since then. There is however, a little white smoke sometimes on start up though. But not enough to notice unless you are the wakeboarder in the water.

prestige · Outlaw Joined: 20 Jul 2003 Posts: 133 City: Kelowna

MrBlean · Posted: Sep 11, 2003 9:54 am Post subject: white smoke

breezer - that doesn't sound too serious, if at all. Another thing you could try easily is a compression check on all 8 cylinders. You can buy the tool (gauge on flexi-hose that screws into spark plug hole) from an auto store. Consistency between cylinders is probably more important than the absolute value (unless it's very low). They usually come with instructions.

However, if it runs OK, I wouldn't lose too much sleep over it.

Breezer · Outlaw Joined: 17 Jan 2003 Posts: 246 City: Austin

Thanks for all your help MrBlean. I may buy that tool if it doesn't cost too much.

MrBlean · Posted: Sep 11, 2003 11:10 am Post subject: Tool

I saw someone quote $10 elsewhere on this site but I'd have thought $25-$30 is nearer the mark. I have one and like all tools, it's nice to have when you need it and they don't cost anything to run!

For background info, take a look at:

http://www.svttexas.com/Tech/PDF/CompressionTest.pdf

(This article says testers cost around =$25)

http://www.motorcyclistonline.com/howto/howtocompression/

and for the de-luxe version of the tool:

http://toolcraze.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=T&Product_Code=TA3DCTK&Category_Code=comp

Partyb · Posted: Sep 11, 2003 3:09 pm Post subject:

Mr. Blean, you really seem to know what you are talking about. From this post and others. So, I have another question re: impellars. It is high time I change my impellar, it's been like almost 300 hours/1.5 years. However, when I took off the housing cover the darn thing looks brand new. I run in fresh water. I am of the school, if it is not broken don't fix it, so I did not change it. Should I change it, or just carry a spare. Now that I am asking questions, I have another. Secondly, I like to do all maintenance myself, as much as I am able. I change the oil and water/gas separation filter every 50 yours. I also recently changed the gas filter and plugs. It has been about 200 hours since I had the compression, timing, and shaft alignment checked. Do you think I should have those items checked, and what else should I have done as maintenance at this point? Thank you very much.

MrBlean · Posted: Sep 12, 2003 4:41 am Post subject: Questions, questions

Partyb
Thanks for the flattery. I am no expert but am a degree-qualified electrical & electronic engineer with a bias toward things mechanical. Hence I apply knowledge, logic and experience (both good and bad) to make informed decisions. I do my own maintenance too (such that there is) but when I don't have the kit, I simply take it (the boat, car, whatever) to someone who does. So, things like changing the oil, filters and plugs etc are things we can all do easily ourselves so, like you, I do.

As for things like alignment and compression, unless you are buying used and wanna check before committing or have some evidence that there's something wrong with these things on your boat, I am also of the school of "if it ain't broke..."

However, the impeller is a different story. The cost of replacing an impeller versus the cost of the consequent repairs if/when it fails is a no-brainer. Sure, it may look perfect but if you had been compressed and relaxed several hundred thousand times you might not feel as good as you looked Exclamation

If you take the impeller out over winter (if you store your boat rather than use over winter), the impeller will be in far greater shape than if you leave it in. leaving it in leaves it in the same compressed postion all winter. Not only does it then want to stay in this position at the start of next season but is starts up without any surrounding water to lubricate it. Result? Torn blades as the friction between them and the pump body just rips 'em off. So, if you are going to remove it anyway to protect/maintain it, why not replace it? It takes no longer and gives you the peace of mind that it's highly unlikely to fail during the season.

Back in May/Jue time there were a whole load of post here about overheating and wrecked engines. Likely causes? Guess. Same impeller as last season. As I said earlier, the impeller issue is a no-brainer. FYI, I fit a new one every season and carry last year's (removed for storage over-winter) as a spare.

As for scheduled service items at various numbers of hours, I'd check the owner's manual, if you have one (and who does?) Probably worth the investment though. Must get one myself but my motor is full multi-point EFi so if something went wrong I'd have to take it to an expert with the diagnostic kit. Now if it had a carburettor and ignition points, that would be a different story!

Leggester · Posted: Sep 12, 2003 5:11 am Post subject:

Besides, he stays up really late to help us Americans out! Laughing

MrBlean · Posted: Sep 12, 2003 6:14 am Post subject: Staying up late

Yep, when I should be boardin'! In fact, should be off boardin' in a couple of hours. And Leggester, you do know were in a diferent time zone, don't you? Like 5-8 hours difference depending if you're on Eastern or Pacific time.

Leggester · Posted: Sep 12, 2003 6:38 am Post subject:

Yep, that's my point. You're heading out as most of us are going to work/school.

I deal daily with you folks. Seems I get hit by the U.K. every morning, then OZ in the afternoons, Latin America fills in the rest of the day Wink

MrBlean · Posted: Sep 12, 2003 12:11 pm Post subject:

Actually that's not true (of me). 'cos I go out first thing in the morning before work, I'm riding when you're getting tucked up for bed. That way get still water and have the place to ourselves. Also gives you a nice smug feeling when you're sitting at your desk knowing you had an hours great fun whilst most of the other schmucks were fighting their way to work on the freeway.

Partyb · Posted: Sep 12, 2003 5:17 pm Post subject:

Thanks MrBlean. My boat is wet all year round (florida)

MrBlean · Posted: Sep 12, 2003 8:25 pm Post subject: Wet all year