2000 Johnson 15hp .What Compression and spark plugs?

[ktyamaha36]

I have a Yr 2000 Johnson 15hp electric start engine. Ive never serviced it yet and its starting to have a slight miss to it. What should the compression be on each cylinder? And what Spark plug does this engine call for? Im Run NGK plugs in all of my engines. But this engine came with Champions.

I have 100psi on the top cyl.
90 PSI on the bottom cyl.

Thanks in advance!
Chris

 

[Vic.S]

Re: 2000 Johnson 15hp .What Compression and spark plugs?

Your pressures are just about OK. The difference between them should not exceed 10%

Assuming a 2 stroke ... you dont say!

The currently recommended plugs are Champion QL82C

I cannot find an equivalent in NGK

BPR7HS are listed as equivalent to QL82YC

But you should be running the inductively suppressed "Q" plugs not resistively suppressed "R" plugs. Inductive suppression is denoted by a "Z" in the NGK numbers

QL77JC4 are listed as alternatives in the parts list. The NGK equivalent is BZ7HS-10

If you must run NGKs those perhaps. But they are only equivalents they may not be the best choice.

The note about inductively suppressed plugs applies to all with CD ignition

Note also that with the exception of a few new models, mostly 4 strokes (presumably rebadged far eastern made ones) Champion plugs are the recommended plugs for all Johnsons and Evinrudes

Disregard all the above if a 4 stroke and fit Champion RA8HC. (Or DCPR7E if you must use NGKs)

 

[ktyamaha36]

Re: 2000 Johnson 15hp .What Compression and spark plugs?

Yes it is a 2stroke. Thank you for the info! That helped me out!!