1972 Johnson 4HP Outboard Motor Service Manual, Page 7Get this manual
SPECIFICATIONS Model 4W72 (weedless gearcase) 4R 72 (standard gearcase) hp at 4500 gear ratio drive 17:28 4W72 Model 12:25 4R72 Model Part Number 203230 18" 1316" stainless steel 4R72 Models Standard8" diameter 5-12" pitch, blade Optional8" 4-12", blade 4W72 Models 6-1 4" diameter 5-12" pitch, blades Speed control Weight Engine type and stroke Piston displacement Piston ring sets (2 standard .030" oversize Diameter of ring Width of ring Lbscompression recommended when pressed cylinder, cycle alternate firing 1-9 16" 5.28 1-3 8" stroke inches Single lever, synchronized throttle and spark 4W72 Model34.0 lbs4R72 Model34.5 lbs
Horsepower (B.I.Acertified) Full throttle oprange Test tank with test wheel
4000 to 5000 4100 Part Number 316021 for 4W72 Ptrt Number 316960 for 4R72
Lift vacuum fuel system Fuel Starter Ignition Spark plug
3 galtank and plug in hose gallons Swing-Arm, self-rewinding Flywheel magneto Champion J6J, .030 inch 17-1220-12 foot-pounds .020 inch Part Number 580321 .18 to .22 Mfd
set) Part Number 383920 Part Number 384312 1.563 in(standard) .0625.0615 in1.3 to 2.8 lbs