The Marine units, and all older carburetors prior to the "mod-quad" design released in 1975 use the longer primary metering rods.
Marine unit in particular have a very generous calibration, as they are NOT subject to emission standards, and Marine engines operate heavily loaded without a vacuum advance on the distributor.
It is NOT recomended to lean them up, or set them up like an automotive application.
I would set them up with the original parts.
As far as metering rods, there are quite a few different early style metering rods. The "B" series have a very slight taper to the upper section, and most often used with Old's, Buick and Chevy carburetors that used the early APT system in the baseplate.
Most other early carbs used two step rods, the number stamped on them will indicate the diameter of the upper section, the tips were .026".
They also had metering rods with tapered upper sections for the early carburetors.
Marine carbs should be using the two step rods, but they can be tuned with the "B" series rods if needed.
The most important thing to do for your Marine carb, is upgrade the internal components.
We sell complete kits for them, with upgraded ethanol compatable components, and dozens of parts not found in other kits, that are needed for a complete/correct rebuilding of the carburetor.......Cliff
