Hello, I have a 1964 18402 18hp fastwin that I just bought. The carb looks like someone tried to change the welsh plug with a chainsaw. My question is the main jet. It's a 63d. I have a carb from a 1969 18902B 18hp fastwin here and it uses a 67d main jet. This got me thinking so I checked a few others and a 1968 18802A 18hp fastwin uses a 57d. That's a big drop in fuel at wot. All mentioned use the smaller 18hp carb. The main jet or orifice plug as omc likes to call it is all over for size. Anyone have any ideas where I should be for 18hp here at 500ft elevation 50-95 degrees average? I also have a larger carb here from a 1971 25hp using the same 22ci block. I was thinking of getting a 25hp 22ci intake manifold and bolting it together. Any thoughts on this as well? Been working on old outboards for many years and don't believe that I have read anywhere or heard of anyone trying this. Any way, Thanks for any input.....