Boatsnhoes
Contributing Member
[Posting this partially to ask a question and partially to document this issue for anyone that may run into it in the future]
I realized that the carburetors on my Mark 35a Mercury actually belong on a Mark 75. This is true of two separate motors I bought, so I find it hard to believe it's a coincidence.
Evidence:
Mark 35a carb: https://www.crowleymarine.com/mercury-outboard/parts/1109_7.cfm
Mark 75 carb: https://www.crowleymarine.com/mercury-outboard/parts/1720_110.cfm
Note the addition of the angled tube in the 75 (part numbers 31,32 over on the right hand side of the diagram)
My question is: was this something done in-factory, or was it done by a previous owner. Like I said, this is two motors with the same carb mismatch (both have the 75 carbs), so I doubt it was done post-sale.
My next question is: how do I compensate for this?
It appears as though the 75 additional angled tube would simply provide extra gas to the mix at high revs, which would make sense given that it goes to a stronger engine. Is it possible that I can just turn the thumb screw all the way in, block off that tubing, and then I effectively have the mark 35 carburetor I'm supposed to have?
My theory right now is that the manufacturer started putting Mark 75 carburetors on the Mark 35 midway thru production, and informed the consumers about this workaround to save the expense of making two different carbs.
If anyone has seen something like this before let me know!
I realized that the carburetors on my Mark 35a Mercury actually belong on a Mark 75. This is true of two separate motors I bought, so I find it hard to believe it's a coincidence.
Evidence:
Mark 35a carb: https://www.crowleymarine.com/mercury-outboard/parts/1109_7.cfm
Mark 75 carb: https://www.crowleymarine.com/mercury-outboard/parts/1720_110.cfm
Note the addition of the angled tube in the 75 (part numbers 31,32 over on the right hand side of the diagram)
My question is: was this something done in-factory, or was it done by a previous owner. Like I said, this is two motors with the same carb mismatch (both have the 75 carbs), so I doubt it was done post-sale.
My next question is: how do I compensate for this?
It appears as though the 75 additional angled tube would simply provide extra gas to the mix at high revs, which would make sense given that it goes to a stronger engine. Is it possible that I can just turn the thumb screw all the way in, block off that tubing, and then I effectively have the mark 35 carburetor I'm supposed to have?
My theory right now is that the manufacturer started putting Mark 75 carburetors on the Mark 35 midway thru production, and informed the consumers about this workaround to save the expense of making two different carbs.
If anyone has seen something like this before let me know!
