1975 Johnson 4HP 4R75, 4W75 Outboards Service Manual, Page 7Get this manual
SPECIFICATIONS Model 4W75 (Weedless gearcase) 4R75 (Standard gearcase) hp at 4500 rpm Propeller gear ratio Propeller drive Propeller 17:28 (Weedless) 12:25 (Standard) Part Number 316558 1 8" 1.234" stainless steel Standard 7-12" dia 6" pitch, blade LEXAN Weedless 6-14" dia 6" pitch, blade LEXAN Speed control Weight Single lever, synchronized throttle and spark Weedless34.0 lbsStandard32.3 lbs
Horsepower (B.I.Acertified) Full throttle oprange Test tank rpm with test wheel
4000 to 5000 rpm 4100 rpm Part Number 316021 for 4W75 4550 rpm Part Number 317738 for 4R75
Engine type Bore and stroke Piston displacement
2 cylinder, cycle alternate firing 1-9 16" bore 1-3 8" stroke 5.28 cubic inches
Hi Lift vacuum fuel system Fuel capacity Starter Ignition Spark plug Spark plug gap
3 galtank and plug in hose gallons Swing-Arm, self-rewinding Flywheel magneto AC-M44C, Champion J6J,14mm .030 inch 17-120-1 foot-pounds .020 inch Part Number 580321 .18 to .22 MfdPart No580971
Piston ring sets (2 per set) standard Part Number 383920 .030" oversize Part Number 384312 Diameter of ring Width of ring Lbscompression recommended when compressed 1.563 in(standard) .0625.0615 in1.3 to 2.8 lbs