Sears 3.5 HP motor questions

Hey, I just signed up for this forum and it looks great and very helpful!<br /><br />Anyway, I just bought an old 1968 Sears 3.5 HP two-stroke air-cooled motor for $100. It had been sitting for years in a garage, but the owner kept it clean and greased and drained the gas out of the bowl before storing it. I put it on my boat and it started on the second pull!! I looked up the specifications on it and it said to mix the gas to a 16:1 ratio. That seems a little too rich for me and I don't want to foul a plug out in the middle of nowhere. Someone told me that back in 1968, they used that ratio because of the lower quality fuel and oil. I'm running a 32:1 mix in it now with no problems after several hours of running. Should I keep using this mix or go with the 16:1? Also, where can I find parts for this motor at? Thanks

Re: Sears 3.5 HP motor questions

Why do you bother to ask this question Opie? After all you already know the recommended ratio for your motor and you choose to run what you want. You know way back in 1968 oil came from the same place that it does today. A hole in the ground.

Re: Sears 3.5 HP motor questions

You better stick with the 16:1.Most likely your motor has bronze bearings and it wont last at 32:1.Also your powerhead is air cooled many reccomend Chain saw 2 cycle oil.

Re: Sears 3.5 HP motor questions

Originally posted by alcan:<br /> Why do you bother to ask this question Opie? After all you already know the recommended ratio for your motor and you choose to run what you want. You know way back in 1968 oil came from the same place that it does today. A hole in the ground.

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Woa...hey now. First of all, you don't know the whole story. Second, yes oil may still come from a "hole in the ground" but do you think the refinery is still the same here in 2004, 36 years later? If so, you're about as dumb as your reply.<br /><br />Ok, so I guess you want the whole story right? When I bought this motor, the only info I could find on it was "Sears" and the serial number. I had no idea what the gas/oil ratio was supposed to be, so I put a mix of 32:1 in it, which is pretty much the standard mix for just about all two-strokes today. I thought this was a good mix for now so I wouldn't foul a plug mixing too rich or seize the piston and crank bearings running a lean mix. It took me 3 days to find a website that listed the model information on my engine based on the serial number. I didn't even know what horsepower it was until I looked at this information. That's when I saw the correct oil/gas ratio...16:1. I haven't ran the motor since I saw this and figured I better ask somebody if this would cause an excessive amount of oil nowadays and possibly foul a plug while I'm out in the middle of nowhere. Better safe than sorry isn't it? <br /><br />Anyways, thank you "steelespike" for your very helpful info. Based on what you said I will be running a 16:1 from now on. That was the kind of reply I was wanting, not a bunch of junk from Mr. I know everything about nothing

Re: Sears 3.5 HP motor questions

Hi!
Unfortunately there are still a lot of rude people around. We aren't all like that. JOHN GOOD LUCK

Re: Sears 3.5 HP motor questions

Certified Parts Corporation will have maintanance stuff like carb parts, flappers, needles, gaskets, etc. Better watch out with that carb, though. My neighbor got one same year for $100. It constantly barfed fuel out of the overflow port at the top of the carb. It took me forever to figure out that the needle seated fine in my hand, but it floated in the seat from vibration when running. Turns out Tecumseh used a brass needle seat with a neoprene tipped needle for couple of years in there, then went to a viton seat with aluminum needle. I got really tired of small engine repair people handing me the aluminum needles and insisting it was the right part, and ended up splicing a neoprene tipped weedeater needle to one of the aluminum ones. Been working fine ever since. Brix Enterprises has a good site for these old Sears Tec/Eska outboards, too.

Re: Sears 3.5 HP motor questions

<----yes oil may still come from a "hole in the ground" but do you think the refinery is still the same here in 2004, 36 years later?>

If our current choices of lubricant are now better then great! But everyone (except Steelespike) seems to have slighted the fact that the engine has the same plain bronze bushings on the reciprocating parts that it had the day it trundled off of the production line!
If the engineers who designed it recommended 16/1 then it's a pretty sure thing that those bearings still need it. If the oil is now better it can only help to extend the life expectancy of those bushings.

Never buy the hype of the 'snake-oil' salesmen above the word of the engine design engineers!