Mercury 305 CID, Service Manual, Page: 321 / 967

4B-12 - THUNDERBOLT IV AND V IGNITION SYSTEM 90-823225--1 1096
Distributor Installation
Engine Not Disturbed
1. 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. Refer to “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. Coat any exposed terminals with Quicksilver Liq-
uid Neoprene.
8. Time ignition as outlined under “Ignition Timing.”
Engine Disturbed
1. Locate No. 1 piston in firing 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.
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 spark 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.”