1972 merc 165 spark problem

AaronR

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I just bought an IMP with a 165hp mercruiser. It has spark at the coil, the distributor turns, the condensor, points, and cap are all new but I cannot get any spark to the plug wires.

The previous owner had replaced these items so I am wondering if they had a spark problem too. he mentioned nothing of it, only that the fuel pump went out.

any ideas on things to check?

I mostly just want to hear it fire to make sure bearings and everything are all good before I put much money in it.
 

Don S

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Re: 1972 merc 165 spark problem

What about the rotor? No rotor, no spark to plugs.
 

AaronR

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Re: 1972 merc 165 spark problem

New rotor. sorry, forgot to mention it.

Only thing not new is the coil, and the wires. But I cant imagine every wire being bad because I checked them, and the coil works fine.
 

Don S

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Re: 1972 merc 165 spark problem

If you have spark from the coil wire out of the coil, but not to the spark plugs, you either have a bad cap or bad rotor.
Is the little spring loaded button on the inside center of the cap still in there?
 

AaronR

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Re: 1972 merc 165 spark problem

Yes it is still there, and like I said these items are brand new. What about the ignition point? (spring loaded deal?) hooked to the condensor? Can it be adjusted wrong?

I hate to buy all this stuff again knowing its new. You can tell it has not sparked across this cap and rotor since it was installed.
 

Don S

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Re: 1972 merc 165 spark problem

If you can put the coil wire from the coil about 1/2" from a good clean (no paint) ground, and crank the engine and get a bright blue snappy spark, then everything up to the cap and rotor is good.
 

AaronR

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Re: 1972 merc 165 spark problem

Well I appreciate the advice. I guess I'll guy buy a new cap and rotor and give it a shot tomorrow!
 

achris

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Re: 1972 merc 165 spark problem

How good is the spark out of the coil? Hold the spark wire that comes out of the coil about 1/2" from the engine block... Crank the engine with the ignition key... You should see a fat healthy blue spark... If you see a thin anemic yellow spark, that's not right....

EDIT: Don beat me again... That'll teach me to go out and do some work in the shed... :facepalm:
 

achris

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Re: 1972 merc 165 spark problem

Well I appreciate the advice. I guess I'll guy buy a new cap and rotor and give it a shot tomorrow!

Do the tests BEFORE you buy parts....
 

AaronR

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Re: 1972 merc 165 spark problem

It has great spark coming from the coil. If I'm understanding Don correctly that only leaves the cap and rotor to transfer the spark to the plug wires.
 

AaronR

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Re: 1972 merc 165 spark problem


Is my thinking incorrect? What other test can I do before buying the cap and rotor? Like I said, I didn't think there were bad because both are brand new but I'm at a loss as to what to do next.
 

Don S

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Re: 1972 merc 165 spark problem

It has great spark coming from the coil. If I'm understanding Don correctly that only leaves the cap and rotor to transfer the spark to the plug wires.

Your understanding is correct.
 
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