Urgent! Black Smoke, Low Revs?

[sybobcat]

Have 59Hhp Volvo Penta MD22P blowing black smoke and revs to only 1,800 rpm.
The hull is dirty, but it also happens while tied to the dock.
Any suggestions please?

[cabo_sailor]

Sounds to me like your exhaust elbow may be plugged. If so you'll need to remove it and let it soak in a muriatic acid solution for a few hours to overnight. This is acid so take precautions with gloves and eyeware. Rinse thoroughly before use.

Rich

[Badsanta]

Clean your prop. if your hull is bad your prop is worse. it is also easy to suck up a rope or fishing line. But more than likely the prop is a mass of barnacles and slime. Do you get full RPM not in gear and then in gear low RPM and smoke? exhaust elbow also. Have you used this boat before? Is this a sudden change, or is this after sitting all winter and now just starting?

[Sailndive345]

While you are at it, you may want to see if anything is blocking the air intake to your engine....

Good luck!

Sailndive

[sybobcat]

Thanks for all the suggestions so far. I’m going back to the boat today to try them. and will give an update soon. I’m trying to sell my boat and the buyer won’t settle until this is sorted. The main worry is that the problem exists when out of gear and not moving. Wouldn’t that seem to eliminate the dirty hull & prop?? I removed the air filter and got 3,000rpm and less smoke at the dock, but the problem returned when under way.
I then stopped the boat, and tried it again while out of gear, but the problem persisted.
In two days, I’m getting hauled out to clean the bottom. Any other comments please!!

[Sailndive345]

It's interesting that removing the air filter made such a difference - even if temporary... Where does air enter the engine compartment? Do you have some sort of intake duct that is blocked/flattened by something? One way to eliminate this may be to run (if convenient and safe to do so) with the engine compartment open - see if the same behavior repeats itself....

Just a thought - good luck solving the puzzle!

Sailndive

[moonrsn]

Did you check to make sure fuel fittings and priming screws are tight? I had this happen to me while test running a Volvo in my garage. I tightened up the bleed screw and it worked fine.

[GordMay]

See also a very old discussion “The Smoking Gun “
Interpreting Diesel Exhaust Smoke:
➥ The Smoking Gun

[Fishman_Tx]

Possibly too much fuel, too little air, or a crappy glow plug. Not all the fuel is getting burnt. Slow to catch during start?

[sybobcat]

Thanks to all. With what we now have in hand , I think we can fix the problem.

Cheers....sybobcat

[Badsanta]

Please post what you find. Thanks

[sybobcat]

okay...good idea...I'll post what we find in a couple of days....thanks

[sybobcat]

A marine engineer elminated the black smoke by running the engine for 4 hours at 2,000 rpm while tied to the dock. He says that, due to the engine not being used for several months, rings were probably stuck inside pistons which were freed up with the high rev running. He also adjusted the 'advance/retard' setting of the fuel injector pump. Thanks again to everyone for your input.