Boating Blues

[Dave R]

Originally Posted by Weekend Pundit

Turns out the problem was two-fold: a partially clogged filter at the carburetor fuel inlet and a funky fuel line that was a bit squishy when I checked it. Both were replaced this spring.

Now that the first problem is fixed (I hope), a second has reared its ugly head - rough idle. I think either my son or I accidentally changed the setting on the idle mixture screw so now it's running a bit rich.

There is no setting that works on all engines. Idle mixture is pretty much set by ear. You have to get the timing and idle speed correct, then adjust the idle mixture until it's too lean (screw clockwise) ans stumbles, then richen it up (screw counter clockwise) a smidge, until it smoothes out. If the adjustment was big, you may need to reset the idle speed and timing again.

That said, if you are using the idle mixture to compensate for another problem, it can get frustrating pretty quickly. Make sure the engine has good plugs, wires, cap, rotor; has no vacuum leaks, and has a fresh supply of clean fuel. Also, make sure the choke is operating properly, a stuck choke will cause a rich mixture too.

If you've done all that, and it still idles poorly, it's probably time for a carb rebuild. It's not hard, but you need compressed air, carb cleaner, and very fine wire (to "floss" the gunk out of the smaller fuel openings) to do it right. Great excuse for an air compressor if you don't already have one... IF you do opt to rebuild the carb, be aware that carburetor screws often stick a bit due to the dissimilar metals used in the screws and the carb body. A dab of valve grinding compound (auto parts stores sell it in a toothpaste-style tube on the Permatex rack) on the phillips head screwdriver tip helps prevent the screw driver from stripping the screw heads.