Where is 0 on Mercruiser 120 timing tab (image included)?

[justthisguyyaknow]

My timing tab (shown below) is very worn, and I'm missing two key pieces of information:

#1. Where is 0 at on the tab?
#2. What the the increments of the lines on the tab (I assume 2 degrees each)?

It's a 1969 Mercruiser 120

Does anyone have this info?

 

[Don S]

Re: Where is 0 on Mercruiser 120 timing tab (image included)?

Here is a picture from the manual.

 

[justthisguyyaknow]

Re: Where is 0 on Mercruiser 120 timing tab (image included)?

Wow, looking at the picture I can see the partial 0 easier than looking at the tab with the naked eye. Poor eyesight I guess.

The manual picture does make it easier.

Do you know if the marks are, in fact, at 2 degree increments?

 

[Bondo]

Re: Where is 0 on Mercruiser 120 timing tab (image included)?

Do you know if the marks are, in fact, at 2 degree increments?

Ayuh,... That is Correct...

 

[justthisguyyaknow]

Re: Where is 0 on Mercruiser 120 timing tab (image included)?

Thanks everyone.

Well, it was advanced to 16 btdc (off the tab by about 2 degrees!).

I set it to spec, and strangely it runs a bit rougher when adjusted back to 8btdc (recommended spec from Merc Manual #1).

The plugs are old and a bit fouled, so I'll replace the plugs to see if that helps. I suspect that maybe the fouled plugs take an instant longer to develop a spark??? I doubt it would account for 8 degrees, but new plugs couldn't hurt.

Thanks again for the help.