Old yamaha mariner 40 hp to 50hp conversion

[105mich]

I have a 78-80 mariner 40hp. Is turning that 40hp in 50hp as easy as swapping carbs? Or is there more work involved?

 

[boscoe99]

Using the parts catalogs, compare the parts used on one model with the parts used on the other model. That will tell you the differences.

 

[QBhoy]

Not totally sure, but it’s in my head that the late 70’s 40hp may be a different engine to the slightly higher hp models next to come after. The 55 and 60 were the same basic engine though. Could be wrong.