My H33 is now 2 years old and the engine (Yanmar 3YM30) has done 240 hours with no problem except the well documented heat exchanger changeout. On Saturday, motoring out of the harbour I noticed she felt a bit sluggish so shoved the throttle forward and she would not go beyond 2000 revs. I looked over the back and there was loads of black oil oil coming out of the exhaust. It was not black smoke and I suspected neat fuel oil with the colouring due to mixing with the exhaust. I motored slowly back to the berth and did a few checks. 1. Propellor OK and freeturning. 2. Max revs in gear 2000 3. Out of gear will rev to maximum but still with the mess coming out the back 4. Starts easily and idles happily 5. Took off air filter and ran but no difference. 6. Lub oil level fine. Any one have a clue to the problem or other suggested tests before I get a mechanic in who will probably cost me an arm and a leg while he systematically replaces everything that moves or turns.
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I Had the Exact Problem...
...with my 3HM35F. It was the mixing elbow. I first thought it was oil spewing out the exhaust. Then I realized it was soot. Had the boat towed to a local marina (I was 40 miles from home). They sent a diver down to see if it was fouled - nope. Then tried to rev in neutral and large amounts of soot were expelled. This determined that it was the mixing elbow. Left the boat for a week to be worked on and had it tuned adjusted and new injectors installed (it was due time) at the same time. It ran like a top after that. Check your mixing elbow. 240 hours isn't much, but of you do a lot of idling and battery charging, then that could have "coked" it up. Have your injectors checked, also. Now, roughly same place 4 years later. Suddenly had a loss of power and it started spewing the soot again. This time I slowed down and put the boat in reverse & reved very slightly. A length of line came loose from the prop. It had fouled it and was enough to cause the problem because of fouled prop. Fortunately I fixed it myself, but had a diver go down when I returned home. There was 4' of line still wrapped around the shaft.
...with my 3HM35F. It was the mixing elbow. I first thought it was oil spewing out the exhaust. Then I realized it was soot. Had the boat towed to a local marina (I was 40 miles from home). They sent a diver down to see if it was fouled - nope. Then tried to rev in neutral and large amounts of soot were expelled. This determined that it was the mixing elbow. Left the boat for a week to be worked on and had it tuned adjusted and new injectors installed (it was due time) at the same time. It ran like a top after that. Check your mixing elbow. 240 hours isn't much, but of you do a lot of idling and battery charging, then that could have "coked" it up. Have your injectors checked, also. Now, roughly same place 4 years later. Suddenly had a loss of power and it started spewing the soot again. This time I slowed down and put the boat in reverse & reved very slightly. A length of line came loose from the prop. It had fouled it and was enough to cause the problem because of fouled prop. Fortunately I fixed it myself, but had a diver go down when I returned home. There was 4' of line still wrapped around the shaft.
Black smoke and soot
Black smoke is a "not enough air" indication. Don't check the air cleaner though. To get air in you have to first get the exhaust out. Paul is right, mixing elbow or exhaust plugged up somewhere not allowing the engine to inhale enough air to burn the fuel.
Black smoke is a "not enough air" indication. Don't check the air cleaner though. To get air in you have to first get the exhaust out. Paul is right, mixing elbow or exhaust plugged up somewhere not allowing the engine to inhale enough air to burn the fuel.
I have been dealing with the same problem since September. I have a 2GM20 in a 1981 H30. At first, I had the injectors taken out and serviced. As I'm relatively new to my boat, I have little info about prior maintenance. After replacement, the engine did run more smoothly, but would still not exceed 2000 rpm. When I would push the throttle further, it would just bog down and spew black smoke. My mechanic suggested pulling the head for a look-see. It was badly coked up and one valve was frozen in a partially open position, that cylinder previously had a low compression reading. I gave the go ahead to do a top rebuild over the winter. I suspect that many owners do not understand that these are not low speed engines and do not cruise them at 75-80% of top speed. Also, they most likely do not run them out at about 3,000 rpm for about five minutes after each low rpm run to clean out the carbon. I'm learning the hard, expensive way!
Problem - What problem !
Thanks for your comments guys. As it it peak holiday season down here I could not get a mechanic for at least two weeks so spent yesterday on the boat thinking about the problem. My conclusion was that a new 200 hr engine was unlikely to have some fundamental injector problem. So I ran the engine in the berth in neutral at idle and after about two to three minutes the black muck started clearing and then completely stoppped. I put her into gear and got up to 3000 revs and no problem. So went out into Moreton Bay and ran around for an hour and all was well, other then a trace more visible greyish smoke than usual, but nothing to worry about. My theory as to what happened is this. I picked up a bit of line or something round the prop and did not notice it early enough as I was fiddling around with the sails so the whole exhaust system got filled with with black exhaust. I then put her into reverse and this removed the obstruction without my knowing it, as it took quite a considerable time to completly evacuate the exhaust system of the nasties. There are a few possible holes in this theory, for example why couldn't I get full revs until my return to the boat yesterday. But the fact remains that what appeared as an acute problem has disappeared. Any more comments welcome. Why do marine diesels have so many problems, there would be an uproar if the automtive industry was similarly afflicted.
Thanks for your comments guys. As it it peak holiday season down here I could not get a mechanic for at least two weeks so spent yesterday on the boat thinking about the problem. My conclusion was that a new 200 hr engine was unlikely to have some fundamental injector problem. So I ran the engine in the berth in neutral at idle and after about two to three minutes the black muck started clearing and then completely stoppped. I put her into gear and got up to 3000 revs and no problem. So went out into Moreton Bay and ran around for an hour and all was well, other then a trace more visible greyish smoke than usual, but nothing to worry about. My theory as to what happened is this. I picked up a bit of line or something round the prop and did not notice it early enough as I was fiddling around with the sails so the whole exhaust system got filled with with black exhaust. I then put her into reverse and this removed the obstruction without my knowing it, as it took quite a considerable time to completly evacuate the exhaust system of the nasties. There are a few possible holes in this theory, for example why couldn't I get full revs until my return to the boat yesterday. But the fact remains that what appeared as an acute problem has disappeared. Any more comments welcome. Why do marine diesels have so many problems, there would be an uproar if the automtive industry was similarly afflicted.
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