Spark Plugs for a 1989 85 Force

thimsllib

Seaman
Joined
Aug 7, 2009
Messages
50
I was recently told by a marine mechanic that I should switch from the Champion UL-18V surface gap plugs to a L77-JC4 plug with a .042 gap. He told me that "This plug fixes a problem with the newer unleaded fuels that the 89 year model engines cannot overcome otherwise. It vastly improves idling, low speed (eliminates the rumble & shudder) and burns cleaner at high speed. " However, I read a thread on this forum that says you should only use surface gap plugs because conventional gap plugs can burn a hole in the cylinder? I definitely don't want to do that. Which plugs should I be using? Can surface gap plugs perform adequately with today's fuel and will conventional gap plugs really burn a hole in the cylnder? Thanks.
 

john from md

Commander
Joined
Apr 13, 2008
Messages
2,184
Re: Spark Plugs for a 1989 85 Force

Go and find another mechanic before that guy cost you lots of money. The surface gap plug is the only one specified by the manufacturer for your engine. Anything else is experimenting.

Granted, there are speed shops for boats and cars and airplanes that develop their machines and processes separately from the manufacturer. However, these people have engineers, flow benches and CAD/CAM and have tested their product extensively.

Somehow, I don't think your mechanic has the data to support his suggested changes.

John
 

Unbalanced

Petty Officer 3rd Class
Joined
May 11, 2009
Messages
89
Re: Spark Plugs for a 1989 85 Force

The only time a plug "fixes a problem" is when you replace whatever is in your engine with a brand new Factory Specifed plug... ;)
 

thimsllib

Seaman
Joined
Aug 7, 2009
Messages
50
Re: Spark Plugs for a 1989 85 Force

Thanks guys... he's not my mechanic, just someone who gave me some advice along the way. I'll use the surface gap plugs. Appreciate the input.
 
Top