Originally Posted by hrwj51
I have been rebuilding a 1976 350 GM marine engine, I did away with the points and installed the electronic spark system, this ignition does not have a vacuum advance nor did the prior system. so I just wondering what degrees the timing should be set at.
You need to avoid detonation at all costs in a boat engine that's running most of the time at the torque peak, and w/the throttle at or near WFO.
Most SBC engines w/OEM heads from that era use around 36 degrees of total timing.
You want to set the springs to bring the mechanical advance in starting as early as you can w/o any detonation, and all in by 2800- 3000 RPM. This varies by weight, hull, prop, etc..
Keep a close eye on the plugs if you get out to the max timing- they are your "window" into the combustion chamber. They should have some color (a light to medium tan used to be what was looked for), but w/the unleaded swill that's available now- often diluted w/alky- the color is harder than ever to read correctly. But you want some color, be it tan, gray or whatever- and not stay white.