STRANGE YANMAR 3GM30 PROBLEM

[johndzl]

Hello all, just discovered and registered on the forum - thank you for having me!

I've a 1988 Sun Rise 35, with a Yanmar 3GM30 27hp moored in Portimao, Algarve.

Recently (Easter, triggered the overheat alarm due to water pump impeller degradation, all repaired, seemed to run fine.

Last week, had her out and about but motoring back up river suddenly clouds of black smoke and soot/black water from exhaust at 2000 rpm and above.

So, have had head off and head gasket replaced, primary and engine fuel filters cleaned/replaced and she now runs cleanly astern right up to and past 3000 rpm, but ahead same problem.

Seems like load gets too much at around 2000rpm, but only in ahead. Prop & shaft clear. Selecting ahead from neutral a little clunky.

Any ideas?

A perplexed JDL

[notorious7004]

Seems like an injector pump adjustment/cleanup problem. Have you changed the air filter?

[johncox]

Have you checked the water jacket where it comes off the exhaust..ie the water injected bend may have a carbon build up inside restricting the gas exhaust flow..
John Cox SO44 1990

[runaway]

johndzl said:

Hello all, just discovered and registered on the forum - thank you for having me!

I've a 1988 Sun Rise 35, with a Yanmar 3GM30 27hp moored in Portimao, Algarve.

Recently (Easter, triggered the overheat alarm due to water pump impeller degradation, all repaired, seemed to run fine.

Last week, had her out and about but motoring back up river suddenly clouds of black smoke and soot/black water from exhaust at 2000 rpm and above.

So, have had head off and head gasket replaced, primary and engine fuel filters cleaned/replaced and she now runs cleanly astern right up to and past 3000 rpm, but ahead same problem.

Seems like load gets too much at around 2000rpm, but only in ahead. Prop & shaft clear. Selecting ahead from neutral a little clunky.

Any ideas?

A perplexed JDL

[runaway]

Just a quicky. I have a 37'Jeanneau and had a similar problem. My engine started to smoke badly at about 2k revs. but only grey smoke. Changed the impellor, still the same. Engineer was going to take the head off then I checked the water inlet and it was almost completely blocked with calc. Cut it all out with a sharp knife. Perfect. Don't know whether that'll help. Runaway. (John Shrive)