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Distributor advance Mechanism

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bertg

Regular Contributor
I have a 120hp Mercruiser about a 1979 vintage. I couldn't find any numbers or tags on it when I rebuilt the engine. The rebuild went fine and the engine runs well. I have a concern about the distributor. There is no vacuum or mechanical capability on the distributor. Is this normal or was the mechanical stripped out before I got the boat.

Inquiring mind wants to know. :confused:
Thanks
Bert
 
kghost
I realize that's where it should be but there's nothing there. I checked a schematic of around that year and it didn't show any weights or springs??
Bert
 
not normal, no. I don't know what document you looked at, but every
1979 120 Mercruiser came with a mechanical advance distributor and the service manual shows it in great detail

some of the more modern electronic units may advance electronically (i.e. Delco EST), which may have been swapped into your 1979 engine, but if you have points, you should have springs and weights

Electronic ignition was on Mercruisers (TBolt IV) in 1979, but only on V8's, not the 120 model
 
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Does the rotor have a slotted wheel attached to and underneath it?
If memory serves me, in 1979 this would have been mechanical, and pre-Thunderbolt EST for this engine.
If you do not any mechanical advancing mechanism within the ignition distributor, then it may be possible that it's been changed to an EST system.
EST = Electronic Spark Timing.
This style distributor has ZERO mechanical advancing ability.
EST uses a module that actually delays triggering, and then decreases the delay as RPM dictates via electronic circuitry.

These were also photo eye triggering..... if that's what you have.

There will NEVER be any conventional vacuum advance on a Marine Ignition Ditributor.

.
 
Thanks for the info all. I have breaker points only, nothing electronic. I'm going to search the net and see what I can find.
BTW I was looking at a Midas parts breakdown where there were no advance parts showing, can't remember which engine now but it was a 4 banger in that era.
Thanks again for the info
Bert
 
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