What Champion spark plug for 1976 Johnson 15hp outboard?

[hugh37]

I'm wanting to replace the spark plugs in my 1976 Johnson 15hp outboard. Apparently, the original Champion L7J is no
longer made. Someone informed me I can use Champion J8C (possibly J6C)? Is this one good, or is there a preferred
one that Champion recommends for my engine? Many thanks for any and all quick responses. Hugh

 

[Joe Reeves]

Re: What Champion spark plug for 1976 Johnson 15hp outboard?

If memory serves me right, I believe that the recommended plug was the Champion UL81J surface gap plug. I'll look it up tomorrow.

 

[hugh37]

Re: What Champion spark plug for 1976 Johnson 15hp outboard?

Thanks, Joe. That's the one I'm hearing about. Do you know anything about the Champion J8C...whether it can be used? Again,
many thanks. Hugh

 

[kodibass]

Re: What Champion spark plug for 1976 Johnson 15hp outboard?

On Leeroys ramblings website I think he mentions that this model may run a bit better using the NGK plugs.??

 

[F_R]

Re: What Champion spark plug for 1976 Johnson 15hp outboard?

First off, let me say the 1976 15hp was super notorious for fouling plugs.....any plugs. Actually, I really don't remember which ones worked best.

It has the Lo-Tension magneto, and I don't think it will reliably fire surface gap plugs.

The J8C would be close enough to the L7J in heat range, however it is a shorter thread reach plug and won't reach as far into the cylinder head.

 

[Joe Reeves]

Re: What Champion spark plug for 1976 Johnson 15hp outboard?

I just rechecked as promised via reply #2.... A OMC bulletin dated April 1976 recommends the Champion UL81J plug. Hopefully that works out for you.

 

[hugh37]

Re: What Champion spark plug for 1976 Johnson 15hp outboard?

F_R & Joe, many thanks for your help. Would you recommend the UL81J over the J8C, assuming the former is longer,
and it would be helpful to use a longer plug? In your opinions, should I rule out the NGK B7HS or B6HS? Again, sure
appreciate your efforts. Hugh

 

[Joe Reeves]

Re: What Champion spark plug for 1976 Johnson 15hp outboard?

Ruling out the NGK plugs will need to be your judgement call. Personally, I don't like them.

 

[kodibass]

Re: What Champion spark plug for 1976 Johnson 15hp outboard?

from what I have read on leeroys site, I have come to my own conclusion to the writs posted There, by far the single most informative pages I have ever come across, you can tell by reading this fine collection of work that much came from the school of hard knocks. on the water observations a most importantly YEARS of owning, running & repairing these outboards. I do not own a 76-77 9.9/15 Omc, And I also do not care for NGK plugs but should I ever get one it will have The NGK plugs that the "Machinist" (Lee roy) says will make it run better & foul less.. WHY because every repair I have done using info off his site has been SPOT-ON! JMHO.

 

[F_R]

Re: What Champion spark plug for 1976 Johnson 15hp outboard?

F_R & Joe, many thanks for your help. Would you recommend the UL81J over the J8C, assuming the former is longer,
and it would be helpful to use a longer plug? In your opinions, should I rule out the NGK B7HS or B6HS? Again, sure
appreciate your efforts. Hugh

I dunno, it has been so long ago that I fought those things. Joe indicated the UL81J is a surface gap plug. I'm sort of doubting that, but as I said, I dunno. I think it is a series-gap conventional two-stroke plug. If I'm correct, that may be your best bet. Those motors gave us such a problem with fouling plugs that I developed an extreme distaste for them. We couldn't keep them running one weekend. Best way to fix it...get a newer motor with CDI ignition.

 

[kbait]

Re: What Champion spark plug for 1976 Johnson 15hp outboard?

NGK B7HS work best for '74-'76 9.9/15hp w/low tension magneto. I agree that J/E outboards like champion plugs best, but not in this instance. Gap 'em to .030"

Good luck!

 

[hugh37]

Re: What Champion spark plug for 1976 Johnson 15hp outboard?

I appreciate the excellent responses...a lot of "IMHO's", understandably so. I went with my "gut feeling" (for what it may prove to be worth!) and today bought the NGKs. Again, thanks.