Remove the spark plug on #1 cylinder ( Top on I engines, Upper left viewed from the rear on V outboards, V automotive engines, recalling the first cylinder on the left, leaning over the front of the engine) and and find TDC by slowly turning crankshaft in direction engine normally runs. You will pass the peak and once you know where it is, back up and come back to the point which will remove any slop in your reading or the engine. Mark the spot on the surface where you can't find a mark. Usually under the pointer, the surface at TDC will have a scribe line so a little sanding should make it visible on automotive engines, maybe not on outboard engines. Then find the circumference of the item used for the timing mark. Find your required timing number. Get a fractional inch number: Timing advance degrees/360 = X. For a timing advance of10* BTDC, X = 10 and 10/360 = 0.028
Finding circumference may be a problem if not fine, get it. If problematic, get the diameter of that surface and multiply it by "pi" (3.14) to get the circumference . Then multiply that circumference number x 0.028, keeping the same units as used in your measurements, mark off the distance on that previously marked surface. Put your plug back in and hooked up, attach your timing light and get after it.
