Atomic Four Specifications

Written by Robert Hess
Atomic Four Engine Service
Vancouver, Canada

Universal Atomic Four: UJ, UJR, UJVD
Universal Atomic Four Stevedore: UJS, UJSR, UJSVD

Specifications & Dimensions Models 5101 / UJ - base configuration Atomic Four

5111 / UJS - Stevedore configuration for Canadian market, power limited to 15 hp with intake manifold restriction)

5102 / UJR - reduction gearbox mounted on transmission, 2.04 ratio standard

5112 / UJSR - Stevedore configuration with reduction gearbox mounted on transmission, 2.04 ratio standard

5103 / UJVD - 20 angle Walter V drive gearbox mounted on transmission, 4 gear ratio options including 1:1

5113 / UJSVD - Stevedore configuration with 20 angle Walter V drive gearbox mounted on transmission, 4 gear ratio options including 1:1

  Type Vertical, in line, 4 cycle, L (flat) head
  Serial Number Locations Pre 1969: stamped on right, forward side of block above starter motor

Post 1968: stamped on block above flywheel housing, and on an id tag glued to top of manifold

Post 1977: stamped on block above flywheel housing, on an id tag glued to top of manifold, and on an id tag glued to front of the flywheel housing cover

  Cylinders 4
  Bore 2.562 in
  Stroke 3.125 in
  Engine displacement (swept volume) 64.44 cu in / 1055.98 cc
  Compression Ratio 6.3:1
  Cylinder Block Cast en-block with marine chrome nickel alloy iron crankcase & full length water jackets
  Cylinder Head Marine chrome nickel iron detachable head
  Crankshaft 2 main bearing, high carbon steel, fully counterweighted, statically and dynamically balanced, uses insert bearings
  Connecting Rods Drop forged, high carbon steel, floating piston pin, insert bearings
  Pistons Cast aluminum, flat-top, 3 ring - 2 compression rings and 1 oil control ring, floating piston pin retained by steel circlips, pin offset .005", expansion slot on non-thrust skirt
  Oil pan Marine chrome nickel iron, one piece, partially baffled marine type, integral engine mounts
  Manifold Water jacketed exhaust and intake manifold in one casting. Separate exhaust flange tapped 1 1/4 in NPT bolts to manifold with two 3/8" NC cap screws or studs at exhaust opening at rear of manifold. V drive models use same manifold with cap over rear opening and front opening machined for exhaust flange so that engine can be mounted facing backwards, as required for use of V drive.
  Exhaust pipe 1 1/4 in NPT (pipe thread) galvanized thick wall pipe
  Lubrication Full pressure to mains, connecting rod big ends, idler gear stud, camshaft bearings, transmission sun & planet gear assembly

Marine type fine brass mesh oil pump pickup screen surrounding pickup to retain oil in rough seas and prevent oil pump ingesting air, exterior oil pressure adjustment

  Water jacket cover Removeable block water jacket plate (standard is carbon steel, stainless steel plates available from after-market suppliers)
  Cooling system Constant flow, 2 stage thermostat, rubber impellor water pump (later models)
  Thermostat upper plate height OEM Holley 3 spring: closed (cold) .325 in / open (hot) .625 in

replacement Westerbeke single spring: closed (cold) .2 in / open (hot) .8 in

  Thermostat housing bypass boss depth .4 in - .5 in
  Mechanical fuel pump pushrod size 1.550 in long x .375 in diameter
  Marine gear (transmission) Paragon: combined engine / marine gear lubrication system with marine gear running in engine oil, sun and planet gear type, forward uses multiple plate clutch pack with over-centre pressure and lock, reverse uses clutch band on sun gear housing, the carrier gear assembly is pressure lubricated via a port on the crankshaft rear main bearing, the rear thrust bearing at the drive flange is splash lubricated via a bearing shield which meters the oil to and from the bearing / rear seal.
  Reduction Gear (optional) Single step, internal helical and pinion type, 2.04:1 ratio
  Carburetor Updraft Zenith marine non-drip type carburetor, upturned air horn with flame arrester screen:
1949 - 1968 Zenith Bendix type 61, cast-iron (adjustable main jet)
1969 - 1984 Zenith Bendix type 68, aluminum (fixed main jet)
  Electrical Charging System Post 1967 12 volt DC, 35 amp Motorola marine alternator, transistorized alternator-mounted voltage regulator, 12 volt DC solenoid equipped starter (optional 50 amp Motorola marine alternator was available at extra cost)
  Propeller rotation Right hand (clockwise facing the rear of the propeller)
  Propeller shaft / coupling diameter Direct Drive: in, 7/8 in, 1 in

Reduction Drive: 1 in, 1 1/8 in

V Drive: 7/8 in, 1 in

  Propeller Size
Note: propeller fitted must allow the engine to reach at least 1,800 rpm during hull speed / full throttle testing
2 Blade
Direct drive: 11 x 7, 12 x 6 (most common size), 12 x 7, 13 x 5
2:1 Reduction Drive: 12 x 11, 12 x 12, 13 x 10, 13 x 12, 15 x 8, 15 x 10

3 Blade (recommended for areas with severe currents, winds, tides)
Direct drive: 10 x 6, 10 x 7
2:1 Reduction Drive: 12 x 9, 12 x 10, 13 x 8, 13 x 9

  Crankshaft rotation Clockwise (right hand) viewed from rear of engine output shaft
  Reduction gear ratio options 2.04:1, 3.01:1
  V drive ratio options 1.00:1, 1.29:1, 1.67:1, 2.0:1
  Torque / RPM / HP

  Fuel Original specification was "standard 92 - 94 octane gasoline", later revised to "regular 90 - 94 octane" (when the specifications were written all gasoline contained lead, which was used to raise the octane rating and extend valve seat life). Modern "Regular" 87 or 89 octane non-leaded gasoline is OK as long as the compression is below 120 psi and the ignition timing is set by adjusting distributor at full cruise speed to give maximum tachometer rpm. Octane booster & lead additive is not recommended or necessary.
  Maximum operating angle 15
  Length overall UJ: 26 in, UJR: 31 15/16 in, UJVD: 35 13/16 in
  Height above crankshaft centreline 13.125 in
  Maximum width 18.250 in
  Offset – crankshaft to propeller shaft UJ: 0 in
UJR: 1.042 in
UJVD: na
  Base depth below centreline 6 in
  Weight UJ: 310 lb
UJR: 330 lb
UJVD: 335 lb
  Firing order (#1 cylinder: flywheel end) 1 2 4 3
  Valve timing Inlet valve opens: 5  BTDC
Inlet valve closes: 50  ABDC
Exhaust valve opens: 45  BBDC
Exhaust valve closes: 10  ATDC
  Valve guide dimensions 1.5 in long x .5 in diameter
  Valve length 3.685 in
  Intake valve head diameter 1.500 in
  Exhaust valve head diameter 1.030 in
  Valve spring diameter 1949 – 1967: .785 in
1966 – 1967: .800 in
1968 – 1984: .810 in
  Valve spring free length 1949 – 1967: 1.825 in (coil bound at .760 in)
1966 – 1967: 1.925 in (coil bound at .800 in)
1968 – 1984: 2.075 in (coil bound at .810 in)
  Compression 90 psi – 125 psi, optimum 100 psi
  Alternator drive ratio (through PTO gear & V belt pulley) 1.75:1 (1 turn of engine crankshaft = 1 turn alternator)
  Flywheel ring gear & housing dimensions 1949 – 1967 (Prestolite starter): ring gear OD / flywheel housing ID 11 in

1968 – 1984 (Delco starter): ring gear OD / flywheel housing ID 11.5 in

  Fuel consumption Approximately 4 litres/hour (1 US gal/hour) @ 2,000 rpm under load depending on boat size & winds/currents
  Auxiliary primary fuel filter recommendation Filter mesh size & type rating: 10 micron with water separator section & metal bowl (ie Racor 320R-RAC-02)
Minimum Flow Rating: 15 litre / hour
  Mechanical fuel pump AC Delco mechanical rubber diaphragm type, maximum pressure 3.0 psi
Auxiliary sediment bowl with internal mesh filter
  Electric fuel pump Facet 574A, 12 volts, maximum pressure 4.0 psi
Internal mesh filter accessible by removing cam lock bottom cap
In-line fuse 10 amp
Should be fitted with oil pressure safety switch (Hobbs 76576 - 10 n.o.) to stop pump if engine stalls or ignition switch left in "on" position
  Pipe / Hose Sizes Exhaust flange: 1 1/4 in NPT - 1 1/2 in or 1 /5/8 in hose
Water pump inlet: 3/8 in NPT - 1/2 in or 5/8in hose
Water pump outlet: 3/8 in NPT - 1/2 in hose
Fuel pump connection: 1/8 in NPT - 5/16 in OD copper pipe, double flared or 1/4 in ID hose (alcohol compatible)
Design Changes Engine Specification Updates circa 1949: Serial #?
Zenith series 61-M2AE7 cast iron carburetor with adjustable main jet
Dole thermostat
Auto-lite ignition
Fairbanks Morse magneto (optional)
Auto-lite 6 volt starter
Auto-lite 6 volt generator
Prestolite distributor (1Gw60032E1X)
bronze gear water pump
old style heat exchanger kit (optional)
5 unit control panel with mechanical tachometer, mechanical oil pressure gauge, mechanical water temperature gauge

circa 1962: Serial #?
Jabsco rubber impellor water pump (available as a replacement)
Prestolite 12 volt starter
Leece Neville 12 volt alternator (optional)

circa 1963: Serial #?
Prestolite 12 volt generator
Auto-lite 15 amp 12 volt generator (optional)
Delco Remy 24 amp 12 volt generator (optional)
Prestolite 35 amp 12 volt alternator (optional)
Prestolite 40 amp 12 volt alternator (optional)

circa 1964: Serial #?
Ongaro - Teleflex electric control panel with electric tachometer (optional), electric oil pressure gauge, electric water temperature gauge

circa 1965: Serial #?
"old" Sherwood (7 end cover screws) rubber impellor water pump

circa 1967: Serial #79476
new style cylinder head with thermost housing
Holley thermostat
new style Sendure heat exchanger kit (optional)
Medallion 6 unit control panel with electric tachometer (optional), electric oil pressure gauge, electric water temperature gauge

circa 1967: Serial #170509
Zenith series 68-7 alumininum alloy carburetor with fixed main jet
Delco Remy distributor (#1112446 - 2G11/6C16/3HI8)
Delco Remy 070FLX 12 volt coil
Delco Remy 1107679starter and new ring gear to fit
larger flywheel housing to fit new ring gear
Motorola 35 amp 12 volt alternator
Motorola 51 amp 12 volt alternator (optional)
Oberdorfer model 202M3 rubber impellor water pump (fitted to most engines)

circa 1967: Serial #171514
external valve chamber oil line no longer fitted

circa 1968: Serial #174340
Oberdorfer model 202M3 water pump standard

circa 1969: Serial #174802
new style valves (stamped "Eaton" or "Etn")

circa 1969: Serial #175503
new transmission housing, oil fill moved to front

circa 1970: Serial #176500
valve guide inner diameter revised to .3145 - .3150 in (new valve guide/valve stem clearance specification of .003 - .004 in to prevent valves sticking in guides)

circa 1972: Serial #178801
Paragon marine gear updated with new outer plate combined with pressure plate, and new wider metric gear carrier ball bearing

circa 1975: Serial #192787
new style deep flywheel housing and flat sheet metal cover

circa 197?: Serial #?
new style electric instrument panel (electric tachometer optional)

circa 1979: Serial #202987
mechanical fuel pump replaced with Facet electric fuel pump and low oil pressure shut-off switch

circa 1980: Serial #20?
production stopped (sales continued to 1984)

     
Wear Limit Sizes/Clearances Bore Std size: 2.562 in – 2.563 in
.010 in oversize: 2.572 in – 2.573 in
.020 in oversize: 2.582 in – 2.583 in
  Piston skirt clearance .001 in - .002 in (.0015 in feeler blade to 5 lb pull)
  Piston ring gap .007 in - .015 in
Note: ensure replacement Hastings or Ertel oil ring bottom spring end gaps are over oil drain slot in bottom of oil ring land

replacement Hastings piston rings are configured as follows:
top groove: bevel on inside of ring - UP
second groove: lip on outside of ring - DOWN
oil ring inner spring: gap over piston vertical expansion slot / ring land slot
oil ring: EITHER SIDE UP

Note: Install rings with gaps staggered 120 degrees around piston. Do not locate any gaps on thrust side

  Piston ring side clearance Top (compression): .0015 in - .003 in
Middle: .001 in - .0025 in
Bottom (oil): .001 in - .0025 in
  Piston pin diameter .6880 in
  Piston pin rod bushing ID .6885 in - .6900 in
  Piston pin clearance in rod bushing (slip fit) .0005 in - .001 in
  Piston pin clearance in piston (push fit) .0001 in - .0005 in
  Oil pump drive end play .001 in - .003 in
  Oil pump gear backlash .003 in - .005 in
  Camshaft gear backlash .002 in - .004 in
  Idler gear backlash .002 in - .004 in
  Accessory gear backlash .002 in - .004 in
  Connecting rod big end side play on crankshaft journal .004 in - .008 in
  Crankshaft end play (at front main bearing) .002 in - .003 in
  Valve seat angle 45
  Valve seat width 1/32 in
  Valve stem diameter .3115 in - .312 in
  Valve stem / guide clearance cast iron guides: .003 in - .004 in (OEM guides are cast iron)
bronze guides in fresh water cooled engines with 180 thermostat: .0035 - .0045 in
  Valve guide internal diameter .3145 in - .3165 in (see valve stem/guide clearance above)
  Valve spring installed length - no cam lobe lift (intake & exhaust) 1.19 in
  Valve spring length - cam lobe full lift (intake & exhaust) .94 in
  Maximum cam lobe lift .239 in
  Valve face angle 45
  Crankshaft main bearing journal Std: 1.9880 in, +.0005 in / -.0000 in
.010 in undersize: 1.9780, + .0005 in / - .0000 in
.020 in undersize: 1.9680, + .0005 in / - .0000 in
.030 in undersize: 1.9580, + .0005 in / - .0000 in
  Crankshaft rod bearing journal Std: 1.5625 in, +.0000 in / .-.0005 in
.010 in undersize: 1.5525 in, + .0000 in / - .0005 in
.020 in undersize: 1.5425 in, + .0000 in / - .0005 in
.030 in undersize: 1.5325 in, + .0000 in / - .0005 in
  Crankshaft marine gear sun & planet carrier bearing journal 1.869 in, +.0005 in / .-.0000 in
  Main bearing clearance .001 in - .0025 in
  Rod bearing clearance .001 in - .0025 in
  Rod big end diameter 1.665 in
  Rod side play on crankshaft journal .004 in - .008 in
  Rod installation Cylinder no stamped on rod big end towards camshaft, #1 rod at front (flywheel end) on #1 piston, #2 rod second from front on #2 piston, etc
  Camshaft bearing journal 1.3745 in, +.0005 in / -.0000 in
  Camshaft bearing clearance .0015 in - .0025 in (line ream after installation)
  Piston installation Arrow on crown pointing to rear (towards marine gear), vertical expansion slot on skirt facing away from camshaft, #1 piston at front (flywheel end), #2 piston second from front, etc
  Piston skirt diameter (bottom of skirt near expansion slot at right angles to pin)

Note: pistons are not round when at room temperature because they are cam ground oval so they expand to round when at engine running temperature

Std: 2.560 in
.010 in oversize: 2.570 in
.020 in oversize: 2.580 in
.030 in oversize: 2.590 in
  Front main bearing width: 1.620 in
  Idler gear shaft diameter .8766 in, +.0000 in / -.0002 in
  Idler gear bushing id .8772 in - .8777 in
  Camshaft bushing inner diameter 1.376 in – 1.377 in
  Oil pump drive end play .001 in - .003 in
  Distance from top of cylinder head spark plug thread to cylinder block deck .980 in - 1.175 in
  Distance from bottom of spark plug thread to cylinder head surface .480 in - .625 in, average approximately .525 in
  Cylinder head combustion chamber volume with piston at TDC (including spark plug hole) 40 cc - 51 cc, average approximately 50 cc
  Cylinder swept volume + combustion chamber volume with piston at BDC (including spark plug hole) 313.5, average approximately 314 cc
  Maximum cylinder bore ovality .002 in
  Maximum cylinder bore taper .008 in
  Maximum cylinder head warp .006 in
  Valve spring compressed length (full lift of camshaft lobe) ?? in
  Valve spring installed height (with valve clearance) ?? in
  Coil primary resistance Internal ballast type: 3 - 4 ohm (standard coil)
(Note: External ballast type (.5 - 1 ohm) is not necessary or recommended. If fitted an external ballast resistor (2 - 3 ohm) must also be installed in series.)
  Starter solenoid current draw

Starter winding currrent draw

approximately 20 amps

approximately 150 amps

  Valve spring pressure ??
  Intake manifold vacuum Idle: 16 in Hg
2,000 rpm under load: 14 in Hg
  Exhaust system back pressure (measured after water injection point) 3 psi / 3 in Hg maximum at full load
  Crankcase sump flow (indicating piston ring and valve guide combustion blow-by) New engine: approximately .25 cfm/+.5" H2O/?psi at full speed / load
Worn engine: approximately .50 cfm/+?H2O/?psi at full speed / load
  Distributor rotor position @ TDC#1 (compression stroke) #1 terminal at 09:00 viewed from front of engine (pointing to extrusion on distributor plate which fits into slot in cap and is also at 09:00)
     
Adjustments Ignition timing Static: No advance = 0  BTDC / Full advance = 17  BTDC
Dynamic: <700 rpm = 0  BTDC / >1,800 rpm = 17  BTDC
  Valve tappet clearance Intake: .008 in hot, .010 in cold
Exhaust: .010 in hot, .012 in cold
  Distributor dwell Prestolite: 38
Delco: 31  - 34 
  Distributor points gap Prestolite: .018 in - .020 in
Delco: .025 in
magneto: .014 in - .018 in
  Spark plug gap .035 in
  Alternator belt tension 3/8 in depression between centres, pressing firmly with one finger
  Oil pressure relief valve 35 psi at 2,000 rpm (or top cruising speed) hot
  Paragon marine gear forward clutch pack approximately 30 - 50 ft lb torque on shift shaft to force 3 pressure plate arms over bulge in throw-out bearing
  Paragon marine gear rear band with gear lever in neutral tighten reverse band adjusting nut (holes in flats so a nail or pick can be used as an adjusting tool) until output shaft turns stiffly, then back off 1 - 2 rotations until shaft turns freely
     
Machining Specs Cylinder head & manifold grinding finish #125 RMS / #112 RA
  Cylinder bore honing finish Hone finish, 60 crosshatch pattern
(Std size bore 2.562 in - 2.563 in)
  Cylinder block deck & manifold finish #90 RMS / #80 RA
     
Lubricants Lubricating oil Depending on installation angle of engine: 4 litres – 6 litres at temperatures over 10C / 50F use SAE 10-30, 10-40, 15-40, SJ or CH-4 rating, to full mark on dip stick (different dip sticks for UJ, UJR, UJVD)
  V Drive Oil .5 litre of SAE 80W90 hypoid oil (SAE 30 motor oil is also acceptable)
  Water pump grease Waterproof grease (white lithium, boat trailer wheel bearing grease, etc)
     
Fastener Torque

Note: Lubricate threads and base of bolt head / nut with oil

Cylinder head stud nuts 35 ft lb, 3 stages: 10 ft lb / 25 ft lb / 35 ft lb, use shop manual torquing diagram or torque from centre of head out to ends. Retorque hot to 35 ft lb after 1 hour of running. Be careful not to exceed 35 ft lb. On older engines stud pull is a common problem. If a stud pulls the threads out of the block remove the head and install a 3/8" NC thread repair insert.

Note: install cylinder and manifold studs into block with gasket cement or Loctite "red", and coat sides of studs with Never-Seize to prevent studs from seizing to head or manifold

  Connecting rod bolt nuts 25 ft lb
  Flywheel stud nuts 35 ft lb
  Main bearing stud nuts 60 ft lb
  Manifold stud nuts 30 ft lb
  Spark plugs 30 ft lb (apply Never-Seize to threads)
  Valve cover cap screws 20 in / lb (with cork gasket)
  Flywheel cover cap screws 85 in / lb
  Idler Gear stud nut 35 ft lb (use red Loctite)
  Oil pump cover screw 12 ft lb (use blue Loctite)
  Oil pan & block 5/16" cap screws 18 ft lb
  Transmission output shaft flange nut 60 ft lb (use tab lock washer)
  Crankshaft channeled gear retaining bolt 25 ft lb (use blue Loctite)
     
Service Parts Spark plugs Specified plug:
Champion #871 (old number RJ8C)

Recommended plug (slightly hotter, helps stop plug sooting):
Champion #592 (old number RJ12C)

Other plugs used (nominal Champion RJ8C equivalents):
NGK BR6S
Bosch W7EC, W7E, W9EC
AC R43, R44, R45
Autolite 304
Motocraft A3C, A3CU, A3X, A5X, A5CU
Denso W20S, W20SR-U, W20S-U

  Contact Breaker (points) Prestrolite Distributor:
Echlin CS-709

Delco Distributor:
Delco D108P
Echlin CS788P
Niehoff DR6 HV

  Capacitor (Condenser) Prestolite Distributor:
Echlin AL38

Delco Distributor:
Delco D203
Echlin RR-176
Niehoff DR-22
Borg Warner G126

  Rotor Prestolite Distributor:
Echlin AL58

Delco Distributor:
Delco 423R
Echlin RR-182R
Niehoff DR-53A
Borg Warner G152

  Cap Prestolite Distributor:
Echlin AL91

Delco Distributor:
Delco D322R
Echlin RR-181
Niehoff DR-74

  Coil Prestolite or Delco Distributor:
Delco 070FLX
Niehoff DR-180 (standard)
Niehoff UN171 (epoxy heavy duty)
Standard UC12

Specifications:
Primary Winding: 12 volt, 3 ohms

  Distributor

 

Prestolite distributor (1Gw60032E1X)

Delco Remy distributor (#1112446 - 2G11/6C16/3HI8) & coil

  HT Leads (spark plug wires) Atomic Four Engine Service A4HTset

Specifications:
Wire type: 7 mm high tension wire, carbon core resistor type
Wire terminals & lengths (add 1 in to length when cutting cable for custom wires to allow for stripping insulation for terminal installation):
Coil/distributor lead: straight terminals, 9 in
#1 plug lead: straight distributor terminal/90 degree plug terminal, 16.5 in
#2 plug lead: straight distributor terminal/90 degree plug terminal, 13.5 in
#3 plug lead: straight distributor terminal/90 degree plug terminal 10 in
#4 plug lead: straight distributor terminal/90 degree plug terminal 8 in

  Generator Prestolite 6 or 12 volt generator:
obsolete - substitute Delco alternator below:

Motorola alternator:
Motorola MR12N4510 - type B (Voltage Regulator 8RG 2010A)
Wilson rebuild 90-05-9089 (voltage regulator 62-05-9651)
Aqua Power rebuild 2834

Specifications:
12 volt alternator (early models were 6 or 12 volt Prestolite generator), negative ground, 35 or 51 amp maximum output, marine-type enclosed brushes behind integral solid state voltage regulator

  Starter Prestolite:
MBG4129 (solenoid Wilson 60-01-6029)

Delco:
Delco 1107679
Wilson 91-01-3736 (starter drive Wilson 61-01-3455, solenoid Wilson 60-01-3541)
Aqua Power 2826

Specifications:
12 volt (early models were 6 volt), negative ground, marine type

Note: Prestolite and Delco starters use different flywheel ring gears

  Alternator belt Dayco: 11A0635 (10A0635 also used)
Gates: 11A0635 (10A0635 also used)
  Engine coolant hoses 1/2" id automotive heater hose & stainless steel gear clamps

water pump outlet to block water plate "T": 10.5 in
block water plate "T" to thermostat housing inlet 90 fitting: 6.5 in
thermostat housing outlet to manifold inlet: 4.5 in

  Temperature Sensor (electric) SW 280ED-F
General Marine GEN26630
Aqua Power AP1943
Faria FAR90405

Specification:
1/2" NPT, 12 volt to match control panel temperature gauge

  Oil Pressure Sensor
(electric)
SW 279A
General Marine GEN24880
Faria FAR90512

Specification:
1/8" NPT, 12 volt to match control panel temperature gauge

  Seawater pump belt (pump over starter) Dayco: 11A770
Gates: 11A770
  OEM flange mounted water pump - gear driven off PTO unit
Used as sea water pump when engine is raw water cooled with no heat exchanger. When heat exchanger is fitted used as engine coolant pump, except when electric pump is fitted, when it is used as sea water pump and electric pump is used as an engine coolant pump.
After 1969 OEM pump was Oberdorfer 202M3 (2 US gal / minute, 15 psi max @ 1,000 rpm)
Cam thickness .105 in (half cam)

Note: 202M3 is usually upgraded to Oberdorfer 202M7 when rebuilt or replaced by installing M7 cam. M7 was used on older diesels
Oberdorfer 202M7 (3 US gal / minute, 20 psi max @ 1,000 rpm)
Cam thickness: .150 in (full cam)

Impellor:
Oberdorfer B6593
West Marine 241044
Globe 815
Barco 815
Sherwood 295628

  Sea water pump used with heat exchanger: belt driven off pulley on end of crankshaft at flywheel, driven directly off end of crankshaft, belt driven using alternator drive belt, or electric motor pump Sherwood R30G / Jabsco 2620-1001 / Oberdorfer 201M (or any pump with a continuous capacity of 6 US gal / minute @ 1,800 rpm and a rpm rating of at least 3,000 rpm)

water pump / crankshaft pulley ratio: 1:1

  Carburetor Jets 1948 – 1968 Zenith 61-M2AE7:
main jet #24, Zenith C52-6-24 & adjustable needle assembly
idle jet #10, Zenith C55-6-10 (.019 in drill size)
well vent jet #22, Zenith C77-18-22 (.043 in drill size)
main discharge nozzle #50, Zenith C66-26-1-50

1969 – 1984 Zenith Bendix 68-7:
venturi #16
float needle & seat #25
main jet #21, Zenith C52-7-21 (.041 in drill size)
idle jet #12, Zenith C55-22-12 (.023 in drill size)
well vent jet #21, Zenith C77-18-21 (.041 in drill size)
main discharge nozzle #55, Zenith C66-114-4-55 (3 x .039 in drill size)
idle bleed hole, fixed plug (.039 in drill size)


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