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. )
Last edited by SteveInMD; 07-14-2008 at 06:34 PM.