difference in spark plugs

[smike26]

I took my new boat for the first time, a 16" Glastron w/ '79 Merc 115, and it ran wonderfully. I had just de-carbed it and was planning on changing plugs after I put it under load for awhile per someone's suggestion. On the second trip with new plugs it wouldn't idle (kept cutting out) and performance was awful. I went from NGK plugs to Champion. These are the type of plugs with no electrode and gap is non-adjustable. I'm 100% that the wires are on the correct cylinders and connections are tight. Could I have a bad plug and what is the best way to test for spark, please be detailed with procedure as I'm new to this. Or do different plugs vary this much from brand to brand? Or do I have another problem altogether?<br />Thanks in advance...

 

[ob]

Re: difference in spark plugs

Smike,First off I recommend using the plugs that are factory recommended for your motor and retest.Secondly it is probable that the plugs are fouled due to recent decarb depending on the amount of buildup that was present.You'll simply have to keep cleaning and or changing plugs out until cylinders are clear of deposits.For the standard plug on your engine I come up with NGK brand standard plug BUHW.Here's a shot of the plug.As you can see it calls for a surface gap. <br />

 

[smike26]

Re: difference in spark plugs

Thanks ob

 

[roscoe]

Re: difference in spark plugs

Clean up the original plugs and put them back in for a test to see if the plugs may be the problem.

 

[Jack Shellac]

Re: difference in spark plugs

I personnally have never had any luck with surface gap plugs unless I was running at almost full throttle all the time. Trolling and slow speeds seemed to make them foul a lot. Went to the standard plug equivalent and didn't have the problem anymore.