1948 3.6 hp scott atwater


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Mike Redmond

Well-known member
Feb 21, 2009
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Got a sunny day today,fired up that oldie,it runs, but,doesnt want to run at full trottle,its got an on n off gasoline supply(it gravity fed)while its running if I turn the gas off it starts to run at full trottle,but it runs out of gas n dies,,,,whats the problem,,guessing it could be the float,,,any ideas out there,,Im not a mecanic, just some guy whould like to see this old engine running and looking for a simple cure for this old girl,,,,Thanks for any imput.
Only a guess here but if it runs full out when your cutting the fuel maybe it's running to lean or rich (not sure which) can you adjust the choke on it?
+1 on the float. I have a '46 Johnson which had a cork float. I read up on this online & found a plastic mercury float that fit with small adaptation. Check out antique outboard website, they have great info.

Edit : I also found several screens in the fuel system about 90% clogged.
Not going to get out of this without going into the carburetor. The fact that you are shutting off the fuel supply and the engine picks up and goes momentarily indicated the engine is rich until you shut off the fuel. It should have a high speed adjustment that you can adjust clockwise until the engine runs at peak RPM. Try it. Lets start there before doing much else. Probably a 16:1 ratio for that engine as well.
Thanks for the info everyone,will fiddle with the adjustments for the rich and lean its got two of them,it didnt have any writings on the engine,someone along the life of the engine painted the whole thing white,,,got to see a picture of it on the net,the two settings are one on top of the other,top setting is for idle,bottom one is for when the engine is running I guess,talked to an old timer this evening,,told me to turn the motor upside down and lightly tap on the carb.says it settles them sometimes,,,not shure about that but guess its worth a try,and your right about the 16 to1 for the oil mix Pappy looks like them old motors had a good appetite for oil lolll,,,
The bottom knob is the HS adjustment. When at WOT turn it until the highest RPM is attained then back it out just a bit. Slow speed adjustment is the same principle. Run it in until the highest RPM is attained then back it out a bit. At this point I would run through this before turning the engine upside down......never heard of that one before.
Finally got the old engine to run properly,did what pappy sugested and almost had it running nice but not quite,so seing I had nothing else to loose tried what an old timer had told me,turned it upside down and gently tapped the carb about ten times with the rubber end of a pair of pliers put it back in the barrel and voila just needed a little tweek and it runs just great wasnt a pleasent day out here predominant winds out here are north easters about 45 f today with the wind chill makes for not exactly a comfy one ,emptied the barrel dont want it to freeze up gets close to freezing at night in this neck of the woods,,,thanks everyone for the advise