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Had to motor more than usual this weekend against a hefty wind. When I brought my 2QM15 up to 2600 -2800 rpm the exhaust turned black and the water being expelled out the back was also black. I usually cruise at around 22-2500 and have had few problems. I do confess that the oil level is slightly high. Not a pint or anything but slightly above the full mark.
Also after stopping the engine and sailing in choppy water, gusty conditions then restarting the engine the exhaust water wasn't sufficient enough to cool the engine. I had to shut her back down and sail some more. I opened up the raw water strainer to see if I had a problem there. None, but when I restarted the engine a few minutes later the flow was once again good. Did opening the raw water strainer break an air lock or did I just luck out? Any advice would be appreciated.
Thanks,
BruceyP
Bruce,
Had the identical problem with my 1GM10. The mechanic said that the load exceeded the design parameters and that incomplete combustion occurred causing the smoke and black water. He suggested getting the injector serviced and to polish the fuel. I also added a little cetane and adjusted the valve clearance to spec and can rev up better now but can still stress the engine at above 3300rpm. The water flow was probably a short term thing as it takes a few seconds for the flow to exit the muffler. That's my guess, as long as the overheating signal didn't go off.
Doug
Under heavy load, my motor will do that. It has been prone to it for at least 15 years. It is unburned fuel. New injector noses improved it about 10 years ago, but it still happens if I really load the motor. You see it often when the motor is loaded at the dockside and the soot builds up on the water.
Mine coughs one puff of black smoke and about a pint of black water at start-up without fail. Then it's smoke-less with clear water. I've always assumed it was the extra fuel in the chamber that was shot in there during the 3 seconds of cranking before ignition.
Black smoke is caused by too much fuel and / or not enough air entering the combustion chamber. Causes can be...
- a blocked air intake
- lack of airflow into the engine room (did you add extra sound insulation?)
- engine room temp too high (causing hot thin air entering the motor) it should be under 130F in there
- excessive load on the engine, such as...
- dirty bottom & prop (especially when combined with a headwind and chop)
- rope caught in the prop (you probably would have noticed strange thumping or vibration)
- forgetting to weigh anchor
The overheating was probably caused by the engine overload. It also points to a possible
- clogged sea strainer
- partially broken impeller in the sea water pump
- heat exchanger core that needs to be removed and cleaned
Also, a exhaust elbow that is partially clogged with carbon could cause both the engine overload (from back pressure) and restrict the seawater flow.
You should work though these, eliminate them as you go until you find the problem. It could be a combination of a few of them. There could be other causes, but these are likely suspects. (Except the anchor thing. )
A sea water air lock did not cause your engine overload and black smoke. Overheating may have been a symptom of the overload. The overheating could have been caused by an airlock or points to a weak cooling system.
The thing I liked about the prybar, is that your hand is further from the barnacles on the work surface. Less chance of getting bitten.
Haven't yet tried paint scraper.
The thing I liked about the prybar, is that your hand is further from the barnacles on the work surface. Less chance of getting bitten.
Haven't yet tried paint scraper.
Barnacles are no joke. They can cause problems that can make you lose a hand. For what it's worth, I won't even go under the boat without dive gloves on.
I agree, but I think a putty knife works better than the pry bar, since it gets under the barnacles more easily. I wear gloves when dealing with the tough little bastages.
Thank you guys for your input. As usual it is appreciated.
Funny you should mention barnacles. My buddy was complaining the other day about having to dive under and clean his prop. A couple of weeks ago I was in the water scraping down the sides because of the buildup, but I forgot to feel around to check the prop. I will check it out next time I'm there. I'm a little un-enthusiastic now since the Red-headed Jellies have returned. Wet suit time I guess.
I will also consider a professional tuneup. This is the second season I have owned her and though I have changed the oil and filters and rebuilt the water pump/replace the impellor, I am reluctant to try to adjust the valves etc. (This is where "if it ain't broke..." starts to break down. Is it broke, or ain't it broke when it is smoking. Can't I just keep her below 2800 rpm and be happy until the season is over?)
As for the water muffler, It was replaced right after launch this year. The condition of the elbow is unknown. (another "how broke is it really" question).
Gracias, mi amigos!
BP
How broke is it? You can probably baby it through the season. If you mostly go on casual day sails or don't mind having to sail home, it's not a huge problem for you right now. If your attitude is that it's a sailboat and you don't care much if the motor works or not, then you're all set. If you sail near busy channels with commercial traffic I would consider it a safety problem.
On the other hand your motor does have a issue, which will probably get worse. I would try to carefully write down the symptoms so you have specific information to give the mechanic. Such as, at what RPM & boat speed does it start blowing smoke? Record the engine temp. as well. Record any headwind, tailwind, sea conditions. Record the temp. in the engine room too. Were you running the engine room blower? The better information you have for the mechanic the more quickly he can find the problem which should $ave you.
Do you know what your max. hull speed is? Maybe you have too much pitch in your prop. and a cooling system the needs to be serviced.
Went to the boat and dove in to check the barnacle situation. I'm surprised it drove the boat at all. It was covered with about 3/4" of marinelife. Twenty minutes of scraping and she was like new. Motored out and she seemed like a different boat. (The admiral has been bugging me about, "Don't you feel that vibration?" My thought was, "What the hell would she know about marine diesel engines?") Well the vibration is noticably reduced, the boat responds to the throttle better, and I took her up to 3000 RPM and no smoke or black water.
But...
Steve,
Thanks for your input. I will take your advice and start keeping a better engine log for future reference.
BP
Umm... might want to listen to the admiral when she says something in the future... I found that was generally the wisest policy in my house.... and even if they don't know much about engines, many admirals do have a very keen sense of when something isn't the way it should be....
Went to the boat and dove in to check the barnacle situation. I'm surprised it drove the boat at all. It was covered with about 3/4" of marinelife. Twenty minutes of scraping and she was like new. Motored out and she seemed like a different boat. (The admiral has been bugging me about, "Don't you feel that vibration?" My thought was, "What the hell would she know about marine diesel engines?") Well the vibration is noticably reduced, the boat responds to the throttle better, and I took her up to 3000 RPM and no smoke or black water.
But...
Steve,
Thanks for your input. I will take your advice and start keeping a better engine log for future reference.
BP
I go over the side at least twice a summer to clean the prop. Besides loading the engine, I lose at least half a knot with a dirty prop. We often swim off the boat and cleaning the prop, checking the centerboard and rudder are normal maintenance things. I keep a masks and fins on the boat for just this reason (and in case I snag a crab pot). I use a putty knife. Works great; sometimes I skin a knuckle, but nothing significant. I like the gloves idea, though.
You might consider pulling your heat exchanger core and cleaning it at some point. You can get a chemical cleaner or a radiator shop can dip it for you. It's usually not a very difficult job. Most marine diesel engine books will show you the steps. I like this one..
I dove down and checked my prop again and found that in the 2 or 3 weeks since last posting here I have grown a new colony of barnacles. Smaller to be sure but they are there. I have a MaxProp and it is bronze. Last year I did nothing to it and I don't remember having much problem (last year was my first full season with the boat). This year I sprayed the prop with some Zinc spray from Pettit that the PO left in a box of odds and ends.
So what do you all use on the prop?
BP
Hi, I have a similar problem. My boat is a Dehler 36db with a Yanmar 2GM20 raw water. The engine used to run smooth and rev up to 2700 easily on load, however lately it is arriving up to 2500rpm (at max throttle on load), and black water and smoke is coming out of the exhaust. Tests conducted till today:
1. Engine starts immediately.
2. Conducted a compression test (by my mechanic) and the result gave around 400psi per cylinder.
3. Taken injectors for a service and injector nozzles have been changed.
4. Inspected stainless steel exhaust elbow and found out to be ok.
5. Tested engine off load and managed to rev it up to 3400rpm.
6. Inspected water locks and found to be ok.
7. Hull and prop are clean (even happened after it was hauled in with new antifouling).
Can someone please guide me on how to proceed? Do you think it is a timing issue? I am asking since I never touched the pump or shims before the fault developed.
Thanks
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