Re: 1975 Sears 7.5 help!
Well then you should check your orange fuel pump bladder for a split, but first you need to reference the Tecumseh engine /carb manual to get a general understanding and the spec's for your carb settings....it will really help you tune your engine and give you a detail on how to set your float. Do a search here at Iboats or google and you should find a link for this very common but "can't live without" Tecumseh manual.
As far as the fuel mix it is 32:1 but I wouldn't be to concerned due to the fact that Tecumseh was all over the place on mix ratio's around 1975, you have a 640-07a engine and this production number marks a change in bearing and rod design to the stainless steal insert and 32 needle rod bearing and aluminum Rod in the 640 series of 2 cycle engines, before this they used a forged steel rod and 66 split needle's and ratios were anyplace from 24:1 to 50:1.
I have one of those 66 bearing models and I run 50:1, 40:1 and sometimes 32:1 basically anything I have mixed up, and other than smoke theres really no performance diffrence except maybe a fouled plug now and then, we have a better burning 2 cycle oil these days so 50:1 is Ok for you outboard but if your worried make it 40:1 and use synthetic.
