Does my engine have the correct spark plugs

[kozman01]

My 1969 Mercury 800 80hp has Champion L77JC4 spark plugs installed by the previous owner. The manual states the L76V. Is this going to harm my engine. I ran it once this year and it ran fine except for some high end running. Is there a great difference in these two plugs? Thanks for any input.

 

[OhNoMrBill1960]

Re: Does my engine have the correct spark plugs

Hey Koz,<br /><br />Check this site out. It has been helpful to me and many others.<br /><br /> http://www.ngksparkplugs.com/apps/default.asp?nav=60000&country=US <br /><br />Good luck,

 

[The Marine Doctor]

Re: Does my engine have the correct spark plugs

The L76V spark plug is a surface gap...and is the proper plug for your engine.<br /><br />The L77JC4 spark plug is the conventional style.<br /><br />TMD

 

[kozman01]

Re: Does my engine have the correct spark plugs

Marine Doc,<br /><br />I just looked at those L77 plugs that are in the engine now and they are the surface gap type. What gives? I looked at some L76's at Walmart and they are the conventional type. Are those L77 installed going to cause me a problem? Thanks for your wisdom....

 

[The Marine Doctor]

Re: Does my engine have the correct spark plugs

The L76V spark plugs come in only one shape and size. Surface gap/ringfire.<br /><br />These and only these are the correct plugs to use.<br /><br />TMD

 

[kozman01]

Re: Does my engine have the correct spark plugs

Thank you sir. I just looked a little closer at my plugs. They are Champion UL77V. I've already taken them out and have replaced them with the 76's that you advise. Maybe this will make my boat run better on the top end then it was the last, and only time, I've taken it out. Thanks again.