View Full Version : Spark Plug question

08-23-2005, 07:48 AM
Curious to know what spark plugs everybody is using and recommends for their outboard applications-
Was just reading about the NGK Surface Discharge plugs- anybody have any experience with these?

08-23-2005, 08:09 AM
In my experience, NGK's are the best plugs to use in outboard applications. Back in my 2-stroke days, I used their surface gap plugs in a 200 merc that was pushing a heavy boat. I could get >100 hr out of them with a lot of trolling at idle speed. As a comparison, I couldn't get more than ~25 hr out of a set of Champions with the standard electrode regardless of the heat range.

You don't need to use surface gap plugs in 4-stroke marine engines. I have gotten over 1000 hr on each of 2 sets of NGK's on my 8 hp Honda trolling motor. I use the hotter of the 2 recommended heat ranges. I probably could have gotten away with just cleaning and re-gapping, but after 1000 hr I figured I would just spend the $6 for a new set. ;D

I have no experience with the newer platinum electrode type plugs in marine engines.

08-23-2005, 08:23 AM
Bassfooler the Doc is correct ;D NGK is what i believe to be the best.I have ran them for years in the bikes also the race cars.Your Money will be well spent for once ;D ;D.
Did you pull the plugs yet and what did thay look like???

08-23-2005, 08:42 AM
Well, both electrodes were black, but didnt seem like they were fouled- definitely blackened with some deposit- the point where the ground electrode attaches to the plug (and the entire diameter of it) definitely shows some fouling- could it be a spark bridging?

08-23-2005, 09:04 AM
Okey BF iam no way an expert on out board motors :-/ but we can do this. The electrodes your talking about are the plug wires? if so we can change them they only last so long.
Changing the plugs wont hurt :o.Even if its doesnt solve the problem it wont hurt to do it ;)

08-23-2005, 09:17 AM
nonono, the ground electrode is the L shaped piece that extends out over the center electrode which creates the gap

08-23-2005, 10:01 AM
Here's a link on how to read plugs.

08-23-2005, 10:50 AM
NGK plugs are the ones. They last a long, long time. I change them every year but in the past I have skipped a year. They dont load up or foul out. NGK in my opinion works period. I have tried a lot of plugs. They are the only plugs to use for two strokes. I would probably put about 400 hours+ a year trolling for trout on them. Wouldnt even consider another plug. Always keep a spare set in your boat in a ziplock bag along with a plug wrench ;).