Mercury Marine MCM 3.0L — Estimating Ignition Timing (Breaker Points)
Adjustments · Ignition System
For the Mercury Marine MCM 3.0L, from the Mercury Marine service manual.
Applies to: General Motors MCM 3.0L / 3.0LX engine
Before you start
- Do not touch or disconnect any ignition system parts while engine is running
Procedure
- Connect timing light to No. 1 spark plug; connect power leads to 12 volt battery.
- Connect tachometer to engine.
- Start engine and run at normal idle speed.
- Aim timing light at timing tab on timing gear cover and crankshaft torsional damper.
- Loosen distributor clamp and rotate distributor body until timing mark lines up with specified mark.
- Tighten clamp and recheck location of timing mark.
- Stop engine and remove timing light.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 8° BTDC (Breaker Points)
- Timing marks in 2-degree increments; set on before side of 0
Source: Mercury Marine service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.