3.0 Liter Mercruiser 140 HP Timing

[JimS123]

I did a complete tune-up recently. The boat runs perfect, so this was just for PM.

The timing was set at 8 deg. BTDC. The spec in the owner's manual calls for 6 deg. This is a 1984 model, originally equipped with point. Its now carrying a pertronics electronic ignition.

I was hesitant to change it because of the good performance. Is there a compelling reason to change?

 

[alldodge]

Not a petronics expert but that setup provides 16, 18 and 20 degrees advance which will equal 24, 26 and 28 total advance.

Your original point distributer provides 35 degrees of total advance with setting at 6 BTDC.

This tells me the petronics distributer will not provide full advance above 2000 rpm so they are setting at 8 to give it a total of 28 degrees IF the red weights are installed in the distributer

 

[achris]

I believe the Pertronix setup just replaces the points. There is no advance in the module. The same springs and weights are still used.

Personally, I would back it off the 6. These engines are known to cause problems with over advanced timing.

Chris.....

 

[JimS123]

I believe the Pertronix setup just replaces the points. There is no advance in the module. The same springs and weights are still used.

Personally, I would back it off the 6. These engines are known to cause problems with over advanced timing.

Chris.....

What are the problems? Apparently its been running at 8 for 6 years now.

 

[achris]

Some engines will spit the head gasket if the timing is too advanced. If it's been like that for 6 years, and you're happy with it, leave it....