How to set base timing on 1989 OMC 3.0L Cobra?

Craig1972

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Mar 2, 2015
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I have two problems. The first being: I have a 2BBL Holley carb (fresh rebuild) that has an open vacuum port (threaded fitting), on the bottom-left corner beside the choke. This port was NOT plugged, or plumbed into anything. Should it be drawing vacuum or not?
Secondly: With this obvious vacuum problem solved, what is the procedure setting the base timing, for a 'points only' (non-electronic) distributor? I've read dozens of threads, but all seem to have electronic advances. I only have the 2 wires, running to the coil.
 

Lou C

Supreme Mariner
Joined
Nov 10, 2002
Messages
11,798
If it's a points distributor then you have to check your dwell angle first with a meter (dwell and point gap are inversely related) and set you idle rpm. Then you can set your base timing. Last go back and re check your idle rpm because they can change slightly after setting the timing. I like to put a few drops of oil on the felt (remove the rotor first) in the center of the distributor shaft . This is to lubricate the mechanical advance mechanism so it does not seize up from corrosion.
That vacuum fitting must be plugged up. Marine distributors do not use vacuum advance. Are you sure it's a marine carb??
 
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Craig1972

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Mar 2, 2015
Messages
4
Thanks Lou! I'm not sure on how to use a dwell meter, but I'll look into it. As for the carb... I was told from a marine dealer, that make and model was stock with a Rodchester carb. The Holley was on when purchased, all my research/ser.#'s tell me it's a Holley Marine 2300 2bbl. But, I will plug off the open port.
 

Lou C

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Nov 10, 2002
Messages
11,798
Dwell meter:
Meter positive goes to coil negative terminal meter negative goes to ground.
Select 4-cyl dwell
It's usually a range of degrees like 37-41.
Too little dwell=point gap too big
Too much dwell=point gap too small.
 
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