Correct spark plugs and spark plug worex for a '61 QD-22 10hp

[kfa4303]

Hi all. Does any one know the correct gauge copper core spark plug wires I need and/or spark plugs for my '61 QD-22 10hp Johnson? I think it's 7mm wire and I've been using Champion J8C spark pugs, but I'm not sure if those are the best ones. I've also heard folks use Champion J6C too. I only ask because, after nearly exhausting my bag of tricks to get this old motor running, I think there's still one more thing I need to try before I use it for target practice or send it down to Davy Jones' locker once and for all.
Thus far I've replaced the impeller, thermostat, clutch dog, points condensers, carb kit, and Lower unit seal kit and got her running well in a test tank, but I get nothing but sluggishness and rattling at WOT while under way. This, along with excess unburnt fuel, leads me to believe the that I'm really only running on one cylinder despite the fact that the motor starts with half a pull, both s'plugs make a spark when grounded to motor and she idles well.
While I was getting spark it was pretty weak. I know it needs to jump a 1/4" gap and since I've already replaced the points and condensers, I assume that means the s'plug wires are the weak link. I snipped a bit off the end and the copper is greenish/gray and brittle and the boots twisted right off in my hands with almost no effort. Am I on the right track, or is there something else I could be missing? These things are so simple I'm not sure what else it could be. I'm at my wits end with this thing if this doesn't do it I'm gonna have to cut my losses and throw it off a cliff..... as soon as I find a cliff in Florida.
Thanks for any help.

 

[jbjennings]

Re: Correct spark plugs and spark plug worex for a '61 QD-22 10hp

7mm copper core wires would be fine. I would NOT run J8C if it were mine, I'd run J6C. J8's are too hot.
You have not mentioned changing the coils. If it were me, I'd change the coil on the cylinder that's got weak spark and the motor will probably run like a swiss watch. New wires are a good idea, too. Just remember to screw the wires onto the coil pin----not just push them on there.
The rattling you mentioned does concern me-----what's the compression on both cylinders? Also, have you checked to see how much slack is in the wrist pins? If it's just the cowl rattling or whatever, of course no biggie. BUt, if you're hearing any kind of knocking noise from the engine, you may have problems.
Good luck,
JBJ

 

[kfa4303]

Re: Correct spark plugs and spark plug worex for a '61 QD-22 10hp

Thanks jb. The rattling is mostly just the face plate rattling around due to the motor running rough. No "knocking" from inside the motor though, so I thnk all the internals are good. These old QDs all have the wobbly, metal face plate for some reason. I'll be sure to switch to J6C and get some new 7mm wire. The coils look good. Obviously replaced at some point, but if the s'plug stuff doesn't do the trick then I guess I'll try coils next. Thanks again.

 

[jbjennings]

Re: Correct spark plugs and spark plug worex for a '61 QD-22 10hp

I just thought that I would add that the points must be spotlessly clean and gapped to .020, and that I hope you're running 24:1 fuel to oil ratio. You can also get new face plate gaskets and such at nymarine.ca, but as you already know, these things can be a little rattle-happy from time to time. Just because a coil looks good, doesn't mean it is. Just one little break somewhere in that spool of wire inside the coil can give weak spark. But you're right, corrosion on wire ends is just as likely since that's what you're seeing!
JBJ

 

[JB]

Re: Correct spark plugs and spark plug worex for a '61 QD-22 10hp

That engine originally called for J4J (now J4C) plugs, but they were prone to foul if operated at idle/troll for extended periods. The J6C prevents that, but for mostly high speed operation the J4C works just a little bit better.

I agree with JBJ that the J8C is far too hot. . .a lawnmower plug.

 

[kfa4303]

Re: Correct spark plugs and spark plug worex for a '61 QD-22 10hp

thanks jb. the points are brand new and gaped properly, but I'll double check when I change the s'plug wires. I'm running 24:1 and the gasket on the cowl is still in pretty good shape. it's just kind of an odd design that they had the sort of floating metal face plate on these old QDs for so long. you don't really notice it when it's running smooth, but it does jiggle around a bit if the motor runs rough. I'll keep y'all posted with what I find. Thanks again.