Originally Posted by RobGallagher
Exhaust could be partially blocked. Flaking metal in a raw water cooled engine can cause a temporary blockage. A collapsing exhaust hose. etc...
Fuel issues, air or spark issues. My old A4 ran once on fuel so bad it looked like chunky soup when I pulled the carb apart, would not rev very high but kept plugging along.
One of the great things about those engines is that they will keep running, just run like crap.
There are many possible answers. You need to duplicate the problem so you can trouble shoot.
It is fresh water cooled.
But the fuel idea is interesting. He did replace the fuel pump recently. I guess if something is blocking the fuel even with the throttle working perfectly it would still cause the rpm's to be low with no lugging.
We did remove the fuel tank and clean it etc at the beginning of the season.
But he did have fuel issues for the last couple of years.
I'm pretty sure I know when the problem will be duplicated. At the worst possible moment.