Surface Gap Plugs in '98 25hp

[jeff_smith_0423]

I'm getting ready to do my winter layup on my '98 Johnson 25hp twin. In the past, I've bought new plugs every year, gapped them, and installed after the motor was fogged so everything was ready to go in the spring.

I notice that L78V surface gap plugs are listed as compatible in this engine. I've run these in the past with my Merc's and LOVED them. Does anyone have any experience with them in the JohnnyRude twins? If they perform well, I'd like to switch.

 

[Daviet]

Re: Surface Gap Plugs in '98 25hp

I normanally take them out and replace them with the electrode type. I don't think they produce a good idle. Are they recommened for your engine?

 

[jeff_smith_0423]

Re: Surface Gap Plugs in '98 25hp

They're on the list:

*20,25,28,30,35 (2-cyl) 1977-THRU? QL77JC4 or QL82C or L78V .030

They're the only recommended plug on the commercial model (although I have no idea what the differences are on the commercial other than badging )

 

[oldrudedude]

Re: Surface Gap Plugs in '98 25hp

I have run them in my '71 50hp rude for two years. The PO had raised electrode plugs in it but the partsman gave me the surface gap when I asked for new plugs. I initially thought the PO was running the wrong plug but subsequently found that both are recommended for my motor. Surface gap plugs are better for WOT running and seem to load up at lower speeds or idling. I'm concidering switching to the raised electrode plug because I putt-putt-putt around a lot more than I run WOT.

 

[EN2]

Re: Surface Gap Plugs in '98 25hp

The QL77JC4 is the best plug to use in your motor for all around use. These plugs have a heat range suited for trolling. The surface gap plugs are suited for constant high speed running, cool plug.

 

[tashasdaddy]

Re: Surface Gap Plugs in '98 25hp

agree with EN2, the surface gap tend to foul out at low speeds. OL77JC4 are a much better all round plug. gapped at .030.

oldrudedude, if you putt putt alot you can open you gag to .035 to .040. to cut down of fouling, that is a very old trick used by those who troll alot.

 

[oldrudedude]

Re: Surface Gap Plugs in '98 25hp

oldrudedude, if you putt putt alot you can open you gag to .035 to .040. to cut down of fouling, that is a very old trick used by those who troll alot.
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Thanks TD, I will give that a try.