Well, this is an interesting topic, something I have wondered about before….
I compared the 68 3hp to the 69 4hp also on marineengine.. They do list a part number for the stripped carb upper body (no shafts/butterflies), and that number is the same for the 3 and 4hp models. So, it would appear as though the venturi size is the same for both models. The throttle valves, nozzle, bowl and high speed needles are different though. I really don’t think the length of the needle valve is the issue, the pans are the same for both years, the low speed needles are the same as well. I guess it makes sense that a change in the design of the high speed needle tip would require a change in the bowl to accommodate it…
Would love to see the bowls/needles and be able to identify the differences. Mixing this stuff up would probably create a nasty carburetor gremlin…
