Universal diesel Model 12 - exhaust smoke

[YoreCrew]

I have had the engine on my 1987 Ericson 28 since I bought it 3 years ago. I do not know the hours. I usually run it no higher than 2100 rpms. But it started giving me a bit of mostly-white smoke. I ran it at 2300 rpm and more smoke came. Looking for an experienced skipper to tell me if this is normal, or ??? Should I run it at max rpm for a while to burn off carbon, do I have a head-gasket issue, or ???

Thanks!

Dick in FL

 

[MarkA]

How much smoke? White smoke usually means water in the fuel, or water leaking into the combustion chamber through a rip in the head gasket.

 

[bayhoss]

I have an 28 with the M12 engine, as well as other things mentioned, overheating can cause an engine to smoke. Also overdoing it will fuel additives will do it as well. I personally overdid it with the Mystery oil in my fuel and white smoke was abundant. Check your engine temp. then check your fuel.

Hope this helps,
Frank

 

[Flight Risk]

Dick,

White smoke in the exhaust is usually a sign of unburned fuel or excess fuel. Sometimes it is the result of water in the fuel. Typically white smoke from a diesel engine occurs when they are cold. Sometimes it is failed glow plugs or low compression. Engines that have been shot with ether starting fluid will smoke white at first but then clean up as they warm up, unless the ring lands are blown out, then it will go to blue smoke..... Carbon will burn of as a combination of blue/black and then clean up after about 15 to 20 minutes at full load. If you have not already done it, check to see if there is a fuel water separator that needs to be drained off. That will resolve the water in fuel side for the short term.

In your case I would do two checks, the first being a pressure test of the cooling system both hot and cold. If the cooling system holds pressure of 10 psi for 10 minutes both hot and cold you can rule out a head gasket issue. NAPA sells a great tester for about 50 bucks. Kind of expensive but good to have since you can test the cooling system during annual maintenance to see if there are leaks, then loan it out in exchange for beers!

Second test would be for compression. You will need a diesel compression gauge and the proper adapters for your engine. Perform a dry cylinder test. Then a "wet" test which involves squirting a small amount of oil into each cylinder and then testing again. Check your manual to see if the compression check is in spec. Due to cost of the compression tester you may want to ask around. Find a diesel tech that will do it on the side for some brews if you are lucky. Most shops will get you 2 to 3 hours labor for this test if you hire a mechanic.

Here are the three colors of diesel exhaust and what they generally mean:

White smoke: Excessive unburned fuel. Common at start up when engine is cold,often made worse by chronic use of ether. Can also be caused by water or gasoline in fuel. Can also be mistaken for steam that is result of failed heat exchanger or riser, rare but I have seen it.

Blue smoke: Usually a result of worn piston rings. Can also be caused by leaking valve stem seals which is fairly common. Excessive lube oil consumption is also typically happening at the same time.

Black smoke: Caused by over fueling from the injection system. Sometimes a sign of engine overloading so back off the throttle and see if the exhaust cleans up. Faulty injectors are a common cause for this too. However, it can also be caused by a clogged air filter! So, if you get black smoke, pull the air filter off and run it before you call a tech to test the fuel injectors.....

Hope this helps out a bit!

Chris
E34 Flight Risk

 

[Loren Beach]

Smokin'

Chris, great reply!
I would only add one tiny bit of trivia to your point about black smoke. I have seen this on a sail boat (more than one, actually) that was over-propped. i.e. usually over-pitched.
When the prop loads up too much and the boat "cannot go that fast" the engine starts putting out smoke and soot.

Like so many things in life where I learn best from the infamous 'school of hard knocks' rather than from books and experts, I learned this one from our boat. The boat came to us with an over-pitched prop and for the first season or two I was too inexperienced to realize that cruising at a sedate 1800 rpm and topping out at the low-mid-20's was wrong...

In smooth water it seemed kind of nice to quietly cruise at such a low rpm.... but we found that we had no power to punch thru a chop... heck, we were probably motoring with about 14 to 16 hp rather than the rated 23 !

Regards,
Loren

 

[Flight Risk]

Thanks Loren!

You are 100% right about over propping a boat. When we put together the prop load curves for even large commercial tugs the engines are specified with a given rpm sweet spot. Marine propulsion is all about a good balance whether it be the 20 to 30 hp engines in our sail boats or the 3000 hp engines common in commercial boats. Reduction ratios of our marine gears are also critical. With the small horse power of sail boat engines, a change from 2.5:1 to 2.3:1 for example, can have a huge impact.

On a side note for props I installed a Max Prop when we re-powered Flight Risk last year. The models showed a 15 inch wheel at 26 degrees for the rated power and designed hull speed of 7.2 knots. 26 degrees is crazy huge for this size engine! Figured with the Max Prop I could always haul out and re-pitch if needed.

On river trials have us turning around 2500 rpm at a tad under 7 knots so I guess the model was right. Rapped out to 3200 we are making about 9 knots on the measured mile! But pay the price........ Fuel burn jumps up to a whopping 2.6 gallons per hour from around less than a gallon per hour at 2500!!! And my transom comes back home covered in black yuck from the overloading. Not really worth the extra couple knots in my book but nice to know we can hammer down if we had too.

Now if I could just figure out the propulsion curves for my main and jib to get 9 knots to weather...........


Chris
E34 Flight Risk