timing bouncing around

[SSTKO81]

1981 Mercruiser 140, timing is bouncing around all over the place when trying to set it. It’s not by much but I need to have it at six and it will fluctuate up to 12 BTDC then back to six. Idle is approximately 900-1000 RPM. So I almost wonder if that’s too high to set it initially.... also quick question on dwell. It’s holding steady around 26, but I’d like to see it closer to 30; do I need to decrease the point gap to increase the dwell?

 

[alldodge]

Idle is approximately 900-1000 RPM. So I almost wonder if that’s too high to set it initially.

Yes to high, get it to 650-700 area, then set at 6 BTDC

Need to change dwell so it reads 28-34 decrease gap

 

[jimmbo]

A decrease in point gap, increases Dwell.
What is the spec? I prefer to set new points with a feeler gauge, record the dwell reading, then use that to reset them as the rubbing block wears
Timing that fluctuates can be caused by bad bearings in the distributor, weak/missing advance springs causing the timing to change and the engine speed to follow along, even a worn/stretched timing chain. Find out the what RPM the timing is set at. Most, but not all are set at idle

 

[SSTKO81]

I’m kinda suspicious of the points... I’ve got the gap set to .017 but the dwell still reads 26*. Is that ok? Gap is below spec but at this point so is dwell. I may just change them out for piece of mind.

 

[jimmbo]

Is your Dwell Meter set for 4 cylinders?

 

[Scott Danforth]

file the points (use your wifes nail file if you dont have a point file)

then set the gap and adjust dwell

your timing is bouncing around because your 39 year old distributor probably needs new bushings.

Napa has bushings for under $5 each.

 

[SSTKO81]

Is your Dwell Meter set for 4 cylinders?

Yes, made sure of that one . Also should I have spark at the points even when the ignition is off? I wouldn’t think so.... but when putting the feeler gauge in there I noticed a little sparkage.

 

[alldodge]

Yes, made sure of that one . Also should I have spark at the points even when the ignition is off? I wouldn’t think so.... but when putting the feeler gauge in there I noticed a little sparkage.

That is the condenser (capacitor) releasing its charge. If it does it more then once I would think a bit more

 

[SSTKO81]

Ok good. Like I said, wasn’t much... it didn’t bite me but wanted to make sure it was normal

 

[SSTKO81]

Something new today. Changed points out and was able to bring idle and timing down to spec, point gap is still under spec but dwell is good so I’m not gonna sweat it. but now that the engine stays running and sounds good; it won’t turn off when I turn the ignition off.... I’d blame the ignition switch but really I’ve never had an issue with it. I’ve had everything from the coil to the alternator disconnected over the last few days so I’m not sure where to start. Any thoughts?

 

[alldodge]

Need a voltmeter
Remove the wires off the + side of the coil. Then measure if any are hot

 

[SSTKO81]

Thanks for the info ALLDODGE. Checked the terminals at the coil and I’ve got 0 on both side with the key off and 9.04 on + with the key on, 8.9 on the negative side. Seems like the switch works. Something must be back feeding the ignition. Maybe the alternator? Incidentally I am using a pertronics 1.5 ohm coil (used to have an igniter but it went out so back to points)

 

[alldodge]

The ALT is about all I could think of because wiring checks out

 

[SSTKO81]

Unhooked the purple exciter wire from the alternator and it works like it should! Looks like I’ll need an alternator. Thanks for the help!