Volvo Penta MD3B overheating

Hi everyone,

I wanted to solicit your feedback on a stupid mistake I made. We were just 10 minutes motoring out when I noticed black smoke coming from the Volvo Penta MD3B engine. I quickly shut down the engine and went to investigate. The smoke was coming from the coolant overflow tank which had blown its cover (I guess it wasn't securely closed, perhaps a good thing). After we got back I looked around and to my horror, noticed that I had the salt water valve closed! So the saltwater wasn't cooling the coolant.

How much damage have I done? Gaskets? The coolant is now murky and thick. What should I do? We sailed back just using the sails but I had to use the engine to dock. I probably ran the engine a few minutes (maybe 5) with the black smoke, and the engine was super hot (hissing) even after we got back.

Thanks much.

Re: Volvo Penta MD3B overheating

How much damage have I done?

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From your discription I would say a complete dissassebly and inspection is in order.

Re: Volvo Penta MD3B overheating

jamh said:

.... The coolant is now murky and thick...... We sailed back just using the sails but I had to use the engine to dock. I probably ran the engine a few minutes (maybe 5) with the black smoke, and the engine was super hot (hissing) even after we got back.....

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I'm not familiar with this particular engine but from what you describe she has taken a beaten! Still, the engine was still operating when you shut it down, so that says it didn't seize.

The first thing I would do is bar over the engine with a torque wrench to establish it turns freely and to get an idea of the torque necessary to turn it. If you have a workshop manual it may tell you what torque it should turn over with. You will now know if its running freely or running tight. In the latter case the motor will need reconditioning. If it turns freely then you will need to change the coolant and the oil. Put in a new oil filter as well. Run the engine and check it exhausts normally. If everythings runs ok you might have dodged a bullet but bear in mind overheat episodes may show up later as a leaking head gasket.


Terry