1964 mercury 9.8 spark plugs

buffwheat

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Jun 18, 2005
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anyone know the correct size spark plugs for a 1964 mercury 9.8 horse, the motor was given to me and had 2 diff plugs jammed into it, ruining the threads. before i repair the treads i need to know what size repair inserts to buy, thank you.
 

dajohnson53

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Re: 1964 mercury 9.8 spark plugs

I think it's a Champion J8C. But you can double check that on any number of web sites- I don't know of this IBoats site has it, but you can check at the oldmercs.com or mercruiserparts.com websites, and probably sparkplugs.com for cross reference info.<br /><br />I don't know the gap. Wild guess would be .030<br /><br />I bought a OEM owner's manual for my old merc 110 and it has spark plug, gap, and other simple maintenance info. I got it at maxrules.com, which is a great company, but again, there's any number of sources. I also bought Seloc (first) and OEM (later) shop manuals. Both seem to work fine.<br /><br />For what it's worth, I've found that the older Mercs spec. Champion plugs and I believe many newer ones spec NGK. I always like to try to get the brand spec'd having been told that the "equivalent" plugs by the various manufacturers are not really totally equivalent. What difference this makes for a 9.8 HP motor, I have no idea.
 

dajohnson53

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Re: 1964 mercury 9.8 spark plugs

PS a ready source for you would be a autoparts store. I always buy my outboard plugs at autoparts stores because they're reasonably priced compared to the boat shops. They have plug info for outboards and can tell you which plug, maybe even the gap. I call first because their stock can be somewhat spotty, but generally within 2 or 3 calls, find the plugs I need for my engines.
 

buffwheat

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Re: 1964 mercury 9.8 spark plugs

thanks man, just found out i got alot more problems then i thought, prolly going to get rid of it and stick with my smaller kicker, thanks for the help
 

dajohnson53

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Re: 1964 mercury 9.8 spark plugs

Originally posted by buffwheat:<br /> thanks man, just found out i got alot more problems then i thought, prolly going to get rid of it and stick with my smaller kicker, thanks for the help
What kind of problems? I've had several with mine and have had some fun (really) fixing them - with help from folks here.
 

buffwheat

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Jun 18, 2005
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Re: 1964 mercury 9.8 spark plugs

plug threads are strpped, not gettin fire to the plugs, power head is Corroded, clutch in lower gear case is bad, leaks compression, pulls start slips.
 
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Re: 1964 mercury 9.8 spark plugs

Hey, member40553. Got any tips on how to mate up the lower unit on my dockbuster? ;)
 

dajohnson53

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Re: 1964 mercury 9.8 spark plugs

Originally posted by technostupeedo:<br /> Hey, member40553. Got any tips on how to mate up the lower unit on my dockbuster? ;)
BFH, JB Weld and duct tape (splurge and get the good stuff!).
 

buffwheat

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Jun 18, 2005
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Re: 1964 mercury 9.8 spark plugs

yea i dont think it's worth fixing, not for me anyway, im hoping to get a partial trade for a desent trailer.
 
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