1996 370DA 7.4L Engine Timing

[hydrotherapy]

The manual for my 7.4L MPI MIE mercruisers refers to a "special procedure" for timing the engine. I suspect it involves a temporary shunt installed in the distributor wiring harness which functions similar to disconnecting/plugging the carb to distributor vacuum line on older cars. Does anyone know or have the procedure that the manual is referring to or point me to where I may find it?

Thanks

 

[PlayDate]

Your engine is controlled by an ECM which manages the fuel injection and ignition (including timing) components. If you want to set the timing properly you really need a scan tool to ensure something else isn't going on with one of the sensors (that usually shows up as an uneven idle). You didn't mention why you felt the timing needed to be adjusted.

The tool Mercruiser techs use can be found: http://www.rinda.com/marine/marine.htm

-John

 

[hydrotherapy]

Thanks John,
I need to time the strbd engine as I had to have it rebuilt over the winter. I did a rough timing and engine run before reinstalling in the boat and now need to get the timing to the correct setting. If it makes a difference, the engines have electronic ignition but are carbureted not fuel injected. I also would like to check the timing on the port engine as other than plugs, rotor and cap it has not been “tuned” in a number of years. If it is a simple procedure, I would like to have the option of doing it myself.

 

[PlayDate]

Huge difference. I read MPI .....Multi Point Injection in your first posting. Carb units are very straightforward. Is the electronic ignition standard Delco or aftermarket (just to make sure I give you the right answer)?

-John

 

[PlayDate]

The following comes from: http://www.perfprotech.com/store/articles/mercruiser-engine-timing.aspx


V6 and V8 Carbureted Models (Thunderbolt V Ignition)

1. Connect timing light (91-99379 or similar) to No. 1 spark plug wire. Connect power supply leads, if applicable, on light to 12 volt battery. Refer to Specifications – “Engine Rotation and Firing Order” for cylinder numbering and location.
2. Connect a shop tachometer to engine.
3. Using a jumper wire, connect the ignition system timing lead (PUR/WHT wire) to a good engine ground (-). This locks the ignition module into the “Base Timing Mode”.

NOTE: Before starting engine make sure the timing tab and marks on damper are clean. Chalk or white paint on timing marks may help visibility.

4. Start engine and run at normal idle speed. Allow engine to reach normal operating temperature.
5. Aim timing light at timing tab, located on the timing gear cover and crankshaft torsional damper.
6. If adjustment is required, 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.
7. Make sure that the distributor has been tightened. Remove the jumper wire from the timing terminal.
8. Remove jumper wire between the timing lead (PUR/WHT wire) and ground (-).

IMPORTANT: Be sure to disconnect the jumper wire from between the ignition system timing lead and ground (-) 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 features would not function.

9. Stop engine and remove timing light.


-John

 

[hydrotherapy]

Excellent - thank you.

 

[PlayDate]

Chuck,

One other suggestion I have is to put timing tape http://www.summitracing.com/search/...-Line/Summit-Racing-Timing-Tape/?autoview=SKU on the damper to make it easier to read the timing reference marks.

-John