ELECTRICAL SYSTEMS
Contents
1. Identification Mark V8 24 Module Advance 24 Degrees Initial Timing 8 Degrees BTDC Total Advance 32 Degrees 35 30 LLI O O zz XE o MAX ar lt _ lt a MIN cs 20 az Qo a2 EZ o 105 59 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 ENGINE RPM LD Index FU FEE 90 823224 2 796 IGNITION SYSTEM 4B 3 MCM 502 MAGNUM MIE 8 2L Identification Mark V8 20R Module Advance 20 Degrees Initial Timing 8 Degrees BTDC Total Advance 28 Degrees 35 LLI 30 Og zz lt 25 lt lt E MAX aZ 20 2 MIN lt z o 15 10 59 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 70808 14 ENGINE RPM Index JPL 4B 4 IGNITION SYSTEM 90 823224 2 796 Repair Precautions When performing the following procedure be sure to observe the following e Be sure that engine compartment is well ven tilated and that no gasoline vapors are pres ent to avoid the possibility of fire Be sure to keep hands feet and clothing clear of moving parts2. Thunderbolt V Ignition System Identification The Thunderbolt V ignition system uses the same distributor as the Thunderbolt system The Ignition Control Module and Knock Control Module are mounted with the ignition control module 73999 a Ignition Control Module b Knock Control Module Index 4B 14 IGNITION SYSTEM ELLE 90 823224 2 796 General Description The Thunderbolt V ignition system has several spark control features that will be described following Idle Speed Spark Control Acceleration Spark Advance Mean Best Timing Spark Advance Over Speed Control Rev Limiter e Knock Retard Spark Control NOTE The Ski models do not have the Mean Best Timing feature Idle Speed Spark Control The ignition module will control ignition timing to maintain a calibrated idle speed This is accom plished by making small spark advance adjustments This feature is only active within a certain RPM range This range may be slightly different from one engine model to another The approximate range is 400 700 RPM Acceleration Spark Advance This feature is active during acceleration only When accelerating the ignition module may add more spark advance to the Base Spark Timing Curve The amount of spark advance added is totally de pendant on how fast RPM increases how fast the throttle is moved This feature is also active within a certain RPM range This range may be slightly differ ent from one engin
3. away from the module and to pre vent corrosion 3 Apply a thin coat of Thermalconductive Grease evenly across the metal back of the ignition mod ule 4 Install ignition module using the stainless steel screws Torque screws to 10 Ib in 1 1 N m 5 Check that terminals of wiring harness connector are clean and free of corrosion Plug connector into ignition module Index 4B 8 IGNITION SYSTEM Distributor Repair Removal 1 Unplug wiring harness from ignition module on distributor housing or disconnect wires from igni tion module mounted on exhaust elbow Discon nect sensor wires 2 Remove distributor cap Do not remove high ten sion leads unless necessary 3 Crank engine over until timing marks line up and rotor is pointing toward No 1 cylinder on distribu tor cap 4 Mark distributor housing in reference to engine block 5 Remove bolt and hold down clamp and remove distributor IMPORTANT To simplify distributor installation do not turn crankshaft when distributor is re moved from engine 90 823224 2 796 THIS PAGE IS INTENTIONALLY BLANK Index FP TEEL 90 823224 2 796 IGNITION SYSTEM 4B 9 Thunderbolt IV Exploded View A 136 a NJ kaw 72058 Index 4B 10 IGNITION SYSTEM 90 823224 2 796 1 Distributor Cap Reassembly 2 Vent 3 Gasket 1 Lubricate shaft with engine oil Install E clip if 4 Rotor removed on shaft in housing Senor W
4. from the timing terminal Adjusting Engine Idle Speed This procedure should be done with boat in the water drive unit in neutral and engine at normal operating temperature Refer to the Operation and Mainte nance Manual for the correct idle speed 1 Disconnect the throttle cable from carburetor IMPORTANT In order to properly set idle speed the ignition module MUST BE locked in the Base Timing Mode This is necessary because of the Idle Speed Control feature that exists in the ignition module See information on the previous pages about this feature 2 Connect a shop tachometer to engine 3 Using a jumper wire connect the ignition system timing lead 13 PUR WHT wire to a good en gine ground This locks the ignition module into the Base Timing Mode 4 Start engine and allow it to reach normal operat ing temperature 5 Adjust idle speed to recommended RPM Stop engine Readjust cable barrel and reinstall the throttle IMPORTANT Be sure to disconnect the jumper wire from the ignition system test terminal before attempting to resume normal operations If the jumper wire is left in place the ignition module will operate in the Base Timing Mode This means that the additional timing advance fea tures would not be functioning 7 Remove the jumper wire from the timing terminal IGNITION SYSTEM 4B 19 Troubleshooting Thunderbolt V Ignition Ignition Control Module Coil Distribut
5. same make and number and heat range Refer to Specifications for spark plug numbers 3 Adjust spark plug gaps with a round feeler gauge Refer to Specifications for proper spark plug gap I v 2 So A 72734 Porcelain Insulator Insulator Cracks Often At This Point Shell Proper Gap Side Electrode Bend To Adjust Gap Center Electrode File When Adjusting Gap DO NOT Bend pooo mo 4 Clean spark plug seating area Do not use gas kets on taper seat plugs Install spark plugs and torque to specifications Where used gasket must be fully compressed to complete heat trans fer and provide a gas tight seal in cylinder For this reason as well as the necessity of maintain ing correct plug gap correct torque is very impor tant during installation IMPORTANT Tapered seat spark plugs are not in terchangeable with non tapered with gasket spark plugs 90 823224 2 796 Spark Plug Wires Inspect spark plugs for damage 2 Check spark plugs for continuity using Multi Meter DVA 91 99750 or similar 3 Replace any wiers that are cracked cut or have damaged spark plug boots 4 Replace any wires that do not show continuity from end to end 5 Reinstall wires in proper order Observe the fol lowing IMPORTANT Proper positioning in spark plug wire supports is important to prevent cross firing IMPORTANT Before installing coil wire to coil apply approximately 1 2 oz of insulat
6. the curing stage of the sealer This acid can cause corrosion on the igni tion components 5 Install sensor into housing and install two retain ing screws Install sensor wheel rotor and distributor cap 7 Connect WHT RED and WHT GRN sensor wires ring terminals on engine harness wires or bullet connectors from ignition module wires Tighten hex nuts securely if so equipped IGNITION SYSTEM 4B 7 Thunderbolt IV Ignition Module IGNITION MODULE MOUNTED ON EXHAUST ELBOW 1 Unplug wiring harness connector from ignition module 2 Remove fasteners and hardware retaining igni tion module to exhaust elbow Remove module NOTE Do not disturb spacers between ignition mod ule plate and exhaust elbow unless replacing Spacers IMPORTANT BLACK ground wire from engine harness must be placed under ignition module fastener when mounting module 3 Replace ignition module using existing hard ware Tighten fasteners securely Be certain BLACK ground wire is in position 4 Check that terminals of wiring harness connector are clean and free of corrosion Plug connector into ignition module IGNITION MODULE MOUNTED ON DISTRIBUTOR 1 Unplug wiring harness connector from ignition module 2 Remove stainless steel screws retaining ignition module to distributor body Remove module IMPORTANT Thermalconductive Grease must be applied to the back of the ignition module to conduct heat
7. Do not touch or disconnect any ignition sys tem parts while engine is running Do not reverse battery cable connections System is negative ground Do not disconnect battery cables while en gine is running Distributor Cap 1 Loosen four distributor cap retaining screws Remove distributor cap Clean cap with warm soap and water and blow off with compressed air 4 Check cap contact for excessive burning or cor rosion Check center contact for deterioration 5 Check cap for cracks or carbon tracks using mag neto analyzer Index 90 823224 2 796 IMPORTANT If high tension leads are removed from cap refer to Spark Plug Wires in this sec tion and the following illustrations for installa tion 72726 a Alignment Notch 72728 a Vent IGNITION SYSTEM 48 5 Rotor Sensor Wheel 1 Remove distributor rotor sensor wheel assembly from distributor shaft Rotor and sensor wheel are secured to the shaft with Loctite Use two flat blade screwdrivers The screwdrivers are posi tioned opposite each other with the blade tips on the underside of the rotor and sensor wheel as sembly Make sure blade tips are toward distribu tor shaft until they come in contact with shaft A downward push on both screwdriver handles at the same time will pry off rotor sensor wheel as sembly The use of torch lamp will also aid in the removal of the rotor sensor wheel assembly Wear protective gloves when
8. ELECTRICAL SYSTEMS THUNDERBOLT IV AND V IGNITION SYSTEM Index Table of Contents Page Thunderbolt IV Ignition System 4B 1 Identification 4B 1 Replacement Parts Warning 4B 1 Thunderbolt IV HEI Electronic Ignition VOL RACE RUUR PEQUUNR R P EYES 4B 1 Torque Specifications 4B 1 Tools Lubricants Sealants 4B 1 Specifications llle 4B 2 s Em 4B 2 Spaik WIGS sso qc sopor FE a gq 4B 2 Firing Order 4B 2 Distributor Advance Curves 4B 3 PP RE 4B 5 Precautions 4B 5 Distributor Cap 4B 5 Rotor Sensor Wheel 4B 6 E UAR RE REA YS 4B 7 Thunderbolt IV Ignition Module 4B 8 Distributor Repair 4B 8 Removal 4 8 Thunderbolt IV Exploded View 4B 10 Disassembly 4B 11 Reassembly 4B 11 Distributor Installation 4B 12 Engine Not Disturbed 4B 12 Engine Disturbed 4B 12 NOTICE For information and procedures on trouble shooting refer to Section 1C Index 4B IGNITION SYSTEM Page Thunderbolt IV Ignition Timing 4B 13 Thunderbolt V Ignition System 4B 14 Identification 4B 14 Gene
9. NOOR OD Index 4B 18 IGNITION SYSTEM rm TO ENGINE HARNESS TO DISTRIBUTOR 91 LHM YNd 9 AYD 9I 4 11 J HO LHM 91 qau LHM 9L M18 9I IGNITION CONTROL MODULE 8 Distributor Wire 9 Battery Positive Wire To Ignition Module 10 Ground Wire For Ignition Module 11 Tachometer Wire 12 Ignition Module Case Ground 13 Timing Lead For Setting Timing and Other Tests 90 823224 2 796 Timing and Idle Adjustment Procedures For Thunderbolt V Ignition Setting Base Ignition Timing 1 Connect timing light to number 1 spark plug Connect timing light power supply leads if applicable to 12 volt source Connect a shop tachometer to engine Using a jumper wire connect the ignition system timing lead 13 PUR WHT wire to a good en gine ground This locks the ignition module into the Base Timing Mode 4 Start engine and run at normal idle speed Allow engine to reach nor
10. e is abnormal mechanical en gine noise rattles or knocks they may give a false knock retard signal If fuel octane is too high or too low a false signal can also be sent TESTING KNOCK MODULE AND SENSOR NOTE A digital volt ohmmeter DVOM and an un powered test light low power test light 300mA or less are needed to conduct the following test Avoid fire or explosion Ensure that engine compartment is well ventilated and gasoline va pors are not present when performing electrical tests inside the engine compartment Sparks generated by electrical tests could ignite gaso line vapors causing fire or explosion 1 Start engine and warm it up to normal operating temperature 2 Connect the positive lead from the DVOM to the PURPLE WHITE timing terminal that comes from the engine harness see previous wiring dia gram Connect the negative lead from the DVOM to a good engine ground With the en gine running there should be 8 10 volts on this circuit If voltage is not present check to ensure that there is 12 volts to the knock module PUR PLE wire Terminal B 3 Advancethe throttle to approximately 1500 RPM 4 Disconnect the harness connector BLUE wire from the knock sensor Connect the unpowered test light to a positive 12 volt source To simu late an AC voltage rapidly tap the knock sensor harness terminal with the test light If knock mod ule and wiring is functioning properly you sho
11. e model to another The approxi mate RPM range for this feature is 1200 4000 RPM Within this range the module can add approximately 10 degrees of spark advance to the base spark timing curve Mean Best Timing MBT Spark Advance During light load cruising the ignition module searches for the optimal ignition timing This is also accomplished by small changes to the spark ad vance At a given RPM the module will try to add a small amount of advance and wait to see if there is an RPM change If RPM increases it will try to in crease timing more The module will continue to ad vance timing until it no longer gets an increase in RPM Conversely if it senses an RPM drop it will start to retard some of the spark timing The approxi mate RPM range for this feature is 1200 4000 RPM Within this range the ignition module can add approximately 10 15 degrees of spark advance to the base spark timing curve Index 90 823224 2 796 NOTE The Audio Warning System is also connected into the ignition module circuit If the audio warning system becomes activated by the closing of one of the audio warning system switches the MBT feature is deactivated Over Speed Control The ignition module will prevent the engine speed from exceeding a preset limit by stopping the spark This feature has an RPM range that varies from mod el to model The over speed limit for a particular en gine is set slightly higher than the top end of the RPM ran
12. g position by following instructions a or b a Remove No 1 spark plug and with finger on plug hole crank engine until compression is felt in No 1 cylinder Continue cranking until pointer lines up with timing mark on crank shaft pulley Index 4B 12 IGNITION SYSTEM b Remove rocker cover and crank engine until No 1 intake valve closes continuing to crank slowly until pointer lines up with timing mark on crankshaft pulley 2 Position distributor to opening in block in normal installed attitude IMPORTANT Make sure oil pump shaft is en gaged in the following Position align oil pump shaft end to engage bottom of distributor dive gear prior to inserting distributor if necessary 3 Position rotor to point toward No 1 cylinder on cap with distributor housing held in installed atti tude then turn rotor counterclockwise approxi mately 1 8 turn more and work distributor down to engage camshaft and oil pump shaft It may be necessary to rotate rotor slightly until engage ment is felt CAUTION Avoid severe engine damage Do not attempt to force distributor into position using hold down clamp and bolt 4 When distributor housing contacts intake man ifold camshaft and oil pump shaft are engaged Install hold down clamp and bolt and snug up bolt 5 Connect distributor ground leads if so equipped 6 Place distributor cap in position and check that rotor lines up with terminal for No 1 spa
13. ge for that model For example if the recom mended range is 4600 5000 RPM the over speed limit would be set at 5100 RPM When RPM reaches this limit spark is turned off until engine RPM drops down to a Reset RPM which would be approxi mately 4750 RPM for this example At this point spark comes back on Knock Retard Spark Control The knock control feature helps provide protection from harmful detonation Knock control is handled by the Knock Control Module This module receives a signal from a sensor that is mounted on the engine block The knock control module works in conjunc tion with the ignition module to retard the timing if spark knock is present IGNITION SYSTEM 4B 15 Thunderbolt V Spark Control Graph IMPORTANT The graph below shows the typical advance ranges for a Thunderbolt V ignition control module The numbers plotted on the graph are not representative of any particular model It is only pres ented to provide an understanding of how the system functions TOTAL SPARK ADVANCE MINUS INITIAL TIMING 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 ENGINE R P M Base Timing Advance Curve Idle Speed Advance Range Knock Retard Range L Acceleration Advance Range MBT Advance Range s Z Index sk gd ll 4B 16 IGNITION SYSTEM 90 823224 2 796 Circuit Description Refer to the circuit wiring diagram on the following page for reference to this circuit description Igniti
14. handling heated ro tor sensor wheel assembly to avoid severe burns 2 With the rotor sensor wheel assembly removed inspect the locating key inside the rotor 3 Thelocating key will appear as a clean edged 1 8 in 3 mm wide sloped ramp at the bottom of the splined hole 72730 Locating Key Screws Senor Wheel Locating Pin O OO 9 Index 4B 6 IGNITION SYSTEM IMPORTANT If there is any doubt if sensor wheel is located properly lay sensor wheel on top of the figure above with sensor fingers facing up to ward you Line up three screw holes and locat ing pin hole on sensor wheel with the figure If wheel is indexed properly all the fingers on wheel will line up with those in the figure 4 fthere are pieces of material shaved off the key or if it appears to have been damaged by being forced down while misaligned with slot in distribu tor shaft the rotor must be replaced 5 Check rotor for burned or corroded center con tact 6 Check rotor for cracks and carbon tracks using magneto analyzer and instructions supplied with analyzer 7 f rotor is damaged replace rotor by removing three hex bolts and separating sensor wheel from rotor Reinstall sensor wheel to new rotor making sure locating pin on rotor is installed in locating hole in sensor wheel Tighten three hex bolts se curely 8 Bend carbon brush tang upward slightly until a distance of 1 4 in 6 mm is obtained between ro tor a
15. heel 2 Install washer on shaft Install original gear slide D Screws 5 onto shaft and install roll pin 7 E Clip 8 Shaft 9 Screws 2 IMPORTANT Hole may be offset and gear will 10 Lockwashers 2 only fit in one direction 11 Sensor 3 If installing a new gear the gear will come drilled 12 Upper Bushing 13 Ignition Module If Equipped Apply Thermal conductive Grease 14 Screws 2 15 Distributor Housing 16 Lockwasher on one side Slide gear onto shaft align hole in gear with hole in shaft Using these holes as guides drill through other side of gear with a 3 16 in carbide tripped drill 17 Nut IMPORTANT If a new gear has only a dimple you 18 Lower Bushing will have to drill through one side of the gear be 19 Gasket fore you slide gear onto shaft In most cases it is 20 Washer recommended to have a machine shop complete 21 Gear the drilling operation for new gear installation 22 Roll Pin Disassembly NOTICE Refer to exploded view preceding for parts identification during disassembly and reas sembly 1 Remove rotor sensor wheel sensor and ignition module if mounted on distributor as previously outlined 2 Remove roll pin washer and driven gear from distributor shaft 3 Check for side play between shaft and distributor housing bushings Maximum side play is 002 in 72735 0 05 mm a Drill Press 4 Remove shaft from housing and check shaft for b 3 16 in Carb
16. ide Tip Drill being bent with a dial indicator and V blocks c V Block Maximum runout is 002 in 0 5 mm d New Gear 4 Install sensor sensor wheel rotor and ignition module if mounted on distributor as previously outlined 5 Install distributor as outlined in Distributor Instal lation Index L 90 823224 2 796 IGNITION SYSTEM 4B 11 Distributor Installation Engine Not Disturbed Install new gasket on distributor housing 2 Turn rotor approximately 1 8 turn in a counter clockwise direction past mark previously scratched on distributor housing 3 Work distributor down into position in engine block with distributor positioned as noted during removal IMPORTANT It may be necessary to move rotor slightly to start gear into mesh with camshaft gear but rotor should line up with the mark when distributor is down in place Distributor shaft must enter oil pump shaft for complete installa tion 4 Replace and tighten distributor hold down bolt and clamp Connect distributor ground leads 5 Install cap Referto Spark Plug Wires and install wires 6 Plug wiring harness into ignition module on dis tributor housing on distributors so equipped Connect wires from ignition module to distributor terminals on all models 7 Coatany exposed terminals with Quicksilver Liq uid Neoprene 8 Time ignition as outlined under Ignition Timing Engine Disturbed 1 Locate No 1 piston in firin
17. ing com poundaround top of coil lead tower Force nipple into coil and wipe off excess Make sure boot does not hydraulically back off the distributor cap terminal Index L 90 823224 2 796 IGNITION SYSTEM 4B 23 THIS PAGE IS INTENTIONALLY BLANK TO ALLOW FOR CORRECTIONS OR ADDITIONS AT A LATER DATE Index Hu FTE 4B 24 IGNITION SYSTEM 90 823224 2 796
18. les and regulations could result in a fire or explosion hazard and should be avoided Thunderbolt IV HEI Electronic Ignition System Torque Specifications Fastener Location In Lb Ft Lb Distributor Gamp 29 2 opark Plugs 14 mm 15 20 DISTRIBUTOR WITH IGNITION MODULE pe 1 1 Ignition Module MOUNTED ON EXHAUST ELBOW iris ens 10 Stainless Steel Tools Lubricants Sealants Description Part Number Timing Light 91 99379 Multi Meter DVA 91 99750 Torch Lamp 91 63209 Insulating Compound 92 41669 1 Quicksilver Liquid 92 27511 2 Neoprene Loctite 271 Thermalconductive Obtain Locally Grease 72722 DISTRIBUTOR WITH IGNITION MODULE MOUNTED ON DISTRIBUTOR BODY a Ignition Module NOTE Except for igntion module replacement re pair procedures for both distributors are the same Index 90 823224 2 796 Specifications Firing Order Coil Primary Resistance 60 80 Ohms G Secondary Resistance 9 400 11 700 Ohms Spark Plugs Firing Order 1 8 4 3 6 5 7 2 Spark Plug 040 In 1 mm Ae AC MR43T Spark Plug Type NGK BR6FS Champion RV15YC4 72008 Index 4B 2 IGNITION SYSTEM Distributor Advance Curves IMPORTANT Distributor advance curve charts do notinclude the initial engine timing Basic initial tim ing must be added to chart for total advance curve The spark advance is controlled by the ignition mod ule MCM 7 4L MCM 454 MAGNUM MIE 7 4L
19. mal operating temperature 5 Aim timing light at timing tab located on the tim ing gear cover and crankshaft torsional damper 6 Adjust timing using the conventional method IMPORTANT Be sure to disconnect the jumper wire from the ignition system test terminal before attempting to resume normal operations If the jumper wire is left in place the ignition module will operate in the Base Timing Mode This means that the additional timing advance fea tures would not function 7 Make sure that the distributor has been tight ened Remove the jumper wire from the timing terminal 8 Stop engine and remove timing light Adjusting Idle Mixture The procedure for adjusting carburetor idle mixture can be found in the appropriate engine service manu al This procedure also requires that the ignition mod ule be locked in the Base Timing Mode IMPORTANT In order to properly set idle mixture the ignition module MUST BE locked in the Base Timing Mode This is necessary because of the Idle Speed Control feature that exists in the ignition module See information on the previous pages about this feature Index 90 823224 2 796 1 Using a jumper wire connect the ignition system timing lead 13 PUR WHT wire to a good en gine ground This locks the ignition module into the Base Timing Mode 2 Adjustidle mixture following the procedure in the appropriate engine service manual 3 Remove the jumper wire
20. nd tang a 1 4 in 6 mm 9 Put2 drops of Loctite 271 into the rotor so it lands on the locating key 10 Put 2 drops of Loctite 271 in keyway on upper portion of distributor shaft 11 Immediately install rotor assembly onto distribu tor shaft Make sure rotor locating key is aligned with keyway in distributor shaft before pressing rotor all the way down on the shaft until it stops with the palm of your hand Let Loctite cure over night with distributor in inverted position ss IMPORTANT The rotor should fit very tight It may be necessary to heat rotor with torch lamp to properly install It is important not to let any Loctite run down distributor shaft Loctite could get into top distributor housing bushing 12 Reinstall distributor cap on distributor 13 Install spark plug wires if removed Refer to Spark Plug Wires in this section Sensor 1 Remove rotor and sensor wheel 2 Disconnect sensor wires 3 Remove two screws that hold sensor into distrib utor housing Remove sensor from housing 72732 a Mounting Screws b Senor Assembly Index 90 823224 2 796 4 Use a magnifying glass and light to inspect the two metal jumper leads for cracks If a crack is found in either metal jumper lead install a new Sensor a Jumper Leads CAUTION Do not use any type of silicone sealer on the in side of the distributor Most silicone sealers give off an acidic vapor during
21. nock sensor s AC voltage signal and then supplies an 8 10 volt signal if no spark knock is present to the Ignition Control Mod ule If spark knock is present the Knock module will remove the 8 10 volt signal to the Ignition Control Module Knock Sensor System a Positive Lead 12 Volts b 8 10 Volts To Knock Sensor c Knock Sensor It is extremely important that the correct knock mod ule and sensor be used for the engine application Using an incorrect knock module or sensor will result in unrecognized spark knock and engine damage The Knock module terminal B is powered by 12 volts from the ignition switch If the 12 volt power source is not present the knock module cannot send an 8 10 volt signal to the ignition control module and a false constant spark retard will result Terminal E of the knock module is the signal line from the knock sensor If this circuit opens or shorts to ground the knock module will never remove the 8 10 volt signal from terminal C to and no spark re tard will occur The ground circuit for the knock mod ule is connected to terminal D If the ground circuit opens the knock module will not be able to remove the 8 10 volt signal and spark knock cannot be con trolled IMPORTANT If knock sensor wire is routed too close to secondary ignition wires the Knock module may see the interference as a knock sig nal resulting in false timing retard Index 90 823224 2 796 IMPORTANT If ther
22. on Control Module e The ignition module receives its power thru the PURPLE wire 9 e Ignition module ground is accomplished thru the BLACK wire 10 e There is also a Case Ground wire 12 that is connected to one of the ignition module attaching SCrews e The 12 volt signal from the ignition module to the distributor is carried thru the WHITE RED wire 8 to the distributor sensor and back to the ignition module thru the WHITE GREEN wire 7 e The tachometer signal is carried to the instrument panel thru the GRAY wire 11 e Ihe PURPLE WHITE wire 3 carries the signal from the knock control module to the ignition control module e There are two BLACK wires 5 that have bullet connectors This circuit is reserved for future options On current models the two BLACK wires must be connected for the system to function properly e The TAN BLU wire 6 carries a signal from the Audio Warning circuit to the ignition module Index 90 823224 2 796 Knock Control Module e The knock control module receives it s power from the PURPLE wire 4 e Knock module ground is accomplished thru the BLACK wire 2 e The PURPLE WHITE wire 3 carries the signal from the knock control module to the ignition control module e The BLUE wire 1 carries the signal from the knock sensor to the knock module Ignition Control System Timing Lead Theignition control sy
23. or Check to ensure that tachometer GRY lead is not shorted to ground at the tachometer or within the harness Check all Terminal Connections at Distributor Ignition Module and Ignition Coil Battery OK Distributor Clamping Screw Tight Check Engine With Key in RUN Position and Instrument Check for 12 Volts at Positive Wiring Harness Terminal on Ignition Coil Volts Battery Cables Key Switch Unplug WHT RED bullet connector from Distributor 0 Check for 12 volts Volts on lead coming from module Heconnect WHT RED bullet connectors Remove High Tension Lead from Distributor to Coil Insert a Spark Gap Tester from Coil Tower to Ground Disconnect Replace Ignition WHT GRN Lead from Distribu Sensor in tor Place Ignition Key in RUN at Coll Position Rapidly strike the Ter minal of the WHT GRN Lead that comes from module against Ground See IMPORTANT below No Spark at Coil Substitute a New Ignition Spark Install New Coil Repeat Above Test at Coil Ignition Coil No Spark at Coil Replace Ignition Module IMPORTANT The WHT GRN lead must be touched against ground 2 3 times per second to simulate a running engine Repeat this test several times to ensure that spark is present St meee TIN 4B 20 IGNITION SYSTEM 90 823224 2 796 Distributor Knock Control Module The Knock Control Module contains solid state cir cuitry which monitors the k
24. ral Description 4B 15 Idle Speed Spark Control 4B 15 Acceleration Spark Advance 4B 15 Mean Best Timing MBT Spark Advance 4B 15 Over Speed Control 4B 15 Knock Retard Spark Control 4B 15 Thunderbolt V Spark Control Graph 4B 16 Circuit Description 4B 17 Ignition Control Module 4B 17 Knock Control Module 4B 17 Ignition Control System Timing Lead 4B 17 Ignition System Wiring Diagram 4B 18 Timing and Idle Adjustment Procedures For Thunderbolt V Ignition 4B 19 Setting Base Ignition Timing 4B 19 Adjusting Idle Mixture 4B 19 Adjusting Engine Idle Speed 4B 19 Troubleshooting Thunderbolt V Ignition 4B 20 Ignition Control Module Coil Distributor 4B 20 Knock Control Module 4B 21 Spark PlugS 4B 22 Spark Plug Wires 4B 23 90 823224 2 796 Thunderbolt IV Ignition Replacement Parts Warning System x AWARNNG Electrical ignition and fuel system components on your MerCruiser are designed and manufac Identification tured to comply with U S Coast Guard Rules and Regulations to minimize risks of fire and explo sion Use of replacement electrical ignition or fuel system components which do not comply with these ru
25. rk plug Install new gasket on distributor housing Install cap 7 Refer to Spark Plug Wires and install wires Re fer to Specifications for firing order 8 Plug wiring harness into ignition module on dis tributor housing on distributors so equipped Connect wires from ignition module to distributor terminals on all models 9 Coat any exposed terminals with Quicksilver Liq uid Neoprene 10 Time ignition as outlined under Ignition Timing 90 823224 2 796 Thunderbolt IV Ignition Timing 1 Connect timing light 91 99379 or similar to No 1 spark plug Connect power supply leads on light to 12 volt battery Refer to Specifications for cylinder numbering and location Connect tachometer to engine otart engine and run at normal idle speed 4 Aim timing light at timing tab located on timing gear cover and crankshaft torsional damper IMPORTANT GM engine timing marks on tab are in 2 degree increments MCM and MIE LH en gines will have A Advance mark to the left of 0 Timing must be set on the A side of 0 Top Dead Center 72851 a Degree Marks b Timing Mark Index 90 823224 2 796 Adjust timing by loosening distributor clamp and rotating distributor body as required until timing mark on damper or pulley lines up with the mark on tab specified in Specifications Tighten clamp and recheck location of timing mark otop engine and remove timing light
26. stem has alead with bullet con nector 11 that is connected into the PURPLE WHITE wire 3 This lead is used for performing the following tests and procedures e Setting Base lgnition Timing e Setting Engine Idle Speed e Setting Idle Mixture e Testing Knock Control Circuit This lead when connected to an engine ground locks the ignition control module into the Base Tim ing mode IGNITION SYSTEM 4B 17 Ignition System Wiring Diagram BLK BLU BRN BROWN GRY GRAY GRN GREEN ORN ORANGE PNK PINK d PUR PURPLE D RED RED oz E TAN TAN 9 v JJ WHT WHITE aS YEL YELLOW LIT LIGHT 4j DRK DARK 3 Hd O L HU x 3 Li 8 CONTROL MODULE Se 2 9 O lt X Knock Sensor Wire Ground Wire For Knock Module Knock Module Signal Wire Battery Positive Wire To Knock Module Ground For Furture Options Audio Warning System Wire Distributor Wire
27. uld see a voltage drop on the DVOM If a voltage drop is not seen check the BLUE wire from the sensor to the knock module for a short or open circuit If the circuit is functioning properly to this point the knock sensor may not be functioning Proceed to the following step 5 Heconnect the knock sensor harness connector to the sensor 6 While still watching the DVOM lightly and rapidly tap on the engine block near the knock sensor with a small hammer If the knock sensor is func tioning properly you should see the voltage de crease If a voltage drop is not seen the knock sensor is faulty IGNITION SYSTEM 4B 21 INSTALLATION OF KNOCK SENSOR IMPORTANT If installing a new knock sensor be sure to replace it with an identical part Knock sensors are very sensitive and designed for each specific application IMPORTANT It is very important that the knock sensor be torqued to the exact specification In correct torquing will result in unsatisfactory per formance DO NOT use sealer on threads 1 Install knock sensor in engine block Torque to 12 16 Ib ft 16 3 21 7 N m gt A 73756 a Knock Sensor 2 Connect electrical connector to knock sensor Index 4B 22 IGNITION SYSTEM Spark Plugs 1 Inspect each plug individually for badly worn electrodes glazed broken or blistered porcelain and replace where necessary 2 Inspect each spark plug for make and heat range All plugs must be the
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