Volvo Penta D1-30 problem

Hi, I'm new here.
I have a newly installed Volvo Penta D1-30 in my boat. It has run for about 55 hours so far, but every 10 hours or so, it starts to run rough, smoke coming out the back etc.
A few times when starting, the engine barely turns over, and runs rough for a little while before it "gets going". This led me to suspect water siphoning back through the exhaust and into the cylinders, but further investigation proved this false. The muffler is installed well within the measurements given in the manual.
My diesel return on the tank is a bit higher than the diesel return outlet on the engine. Could the "back pressure" in the diesel return line induced by this height difference be causing my problems?


Best regards
Tor

Tor,

fuel return line has very little pressure, but by the time fuel is in the Out line, it is out of the system so to speak.

Most likely you have water in the fuel, debris in the tank, or clogged filter.

Another possibility is the lack of fresh air in the engine compartment.....run it with hatch open just to make sure its not choking due to lack of air.