Guys - you can simply swap in the carb off either a similar 25 HP XD series engine or one of the newer marathon series motors - either one will work. The powerhead parts and lower units are all the same for the 18/20/25 HP engines, I've checked plenty of serial #'s on boats.net at this point to verify there are no differences in any of the parts. The intake gasket and intake plates are all made for the 25hp size carb but used on all 3 motor sizes without an issue.

Side by side, can you tell which is which???


Due to the difference being so drastic, and the fact that the casting # from my carburetor (WMC-2) is not listed on the 18/20/25 XD series parts schematics I'm not sure exactly what part I had originally as I'm not the first owner of this engine. when I ordered the rebuild kit every gasket and part in it fit fine except for the idle mixture screw, which fortunately I still had the original one.

Showing the measurement of the main inlet opening to be the same 1 5/16", though the casting internally is totally different.
Original Carb:

25HP Carb:


Engine side of the carbs, 25hp first with measurement of 1 1/4" the outlet from the carb to the engine:


And the original carb with it's 1" engine side outlet


Here's the original carb with the original gasket on it with the 1 1/4" measurement of the new carb's oultet for reference:


The original gasket is definitely larger than the original carburetor outlet...however - when you put that gasket on the intake plate you see that the intake plate is bored to the size needed for the 25hp carburetor



You will notice the fuel pump body on the 25hp carb is significantly wider than the original. This did not create clearance issues with the original throttle plate. All the powerhead part numbers and lower unit parts are the same for the various motors, which makes sense, as everything from the intake gasket on is designed for the dimensions of the 25hp. While not as drastic a HP increase as you'll find available to similarly sized Johnson motors (that can go all the way to 35hp with the right intake and carb combination) it is just as simple an upgrade - slightly easier as you don't need to re-bore or replace the intake (if you want more than 25hp the intake needs to be replaced on the Johnsons.)