McCulloch took over Scott Atwater in 1957, the motors from 1958-9 onward being called Scott and then, by about 1964, simply McCulloch. The 3.6/3.5 series motors had decals that said Scott Atwater, Scott, Scotty and finally McCulloch – however, the ID tags starting in 1957 all said Mfg by McCulloch.

Since you don’t have the full model # you may be able to figure out they year of your example by the tank decals if they are still present. I’m working from memory but ’57-8 would say Scott Atwater on the tank decal, ’59-63 Scott or Scotty and ’64-5 McCulloch. I seem to recall the final versions (’63-5) were rated at 3.5hp rather than the traditional 3.6. (That change may have been due to switching to a Walbro or Carter carb from the Tillotson they had forever…) Someone who is really into the minutae of this model may be able to nail it closer if you can get a photo to post here.

The Scott Atwater 3.6hp family of motors were decent and reliable outboards during their long run from 1947 to 1965. They were a little heavy and a tad loud, but (at least with the Tillotson since that’s what I’ve had the most experience with) ran great and were easy to work on. The "Scottys" have a wobble pump on the driveshaft that is long lasting, the mag is from Wico and subject to the standard problems with coils, condensers and points fungus. The biggest issue I’ve seen is the fuel tanks made out of steel that loved to corode (from the inside out) faster than a ’71 Chevy Vega parked on Daytona Beach. The lower unit uses Lubriplate 105 and will probably get water in it no mater how hard you try to seal it. Fuel/oil mix is 16:1 using TCW-3.

These motors are pretty common, they are a staple of yard sales, flea markets and our AOMCI events with decent looking examples having been seen to change hands in the $10-$50 range. My observation is the supply exceeds demand, your results may vary…..