Plug gap for trolling? - '58 7.5

[Kev]

Using J6J plugs for a 1958 Johnson 7.5, I know the normal plug gap is .030.<br /><br />Is it a good idea to increase the plug gap to .040 or so if we mostly use the motor for trolling? Will that discourage fouling of the plugs? Maybe 90-95% trolling, rest of the time at near full throttle.<br /><br />So far the plugs look OK, but there is a little darkish oily liquid on the spark end of the plugs when I remove them to check. No black or burnt ash, just a little oily wetness. Is that normal? The ceramic is basically still white in color, not beige or gray. The motor is running good.<br /><br />Thanks in advance for any help,<br />Kev

 

[Paul Moir]

Re: Plug gap for trolling? - '58 7.5

I think if you want, you should experiment. The magneto on that thing is only adequate, so opening the gap may lead to troubles. But, if the coils are well set up, the points are clean and the magnet is still nice and strong, then .035 or .040 may make a noticable difference.<br />A little wet sounds right for the plugs with a 24:1 fuel/oil ratio. Which you must absolutely use. You may try experimenting with different brands of TC-W3 to see if your engine is particularly happy trolling on one kind or another too.<br />I'm presuming you've got your mixture controls set properly. It's very important to warm the engine up first before adjusting the low speed needle.

 

[JB]

Re: Plug gap for trolling? - '58 7.5

At one time OMC recommended .040" for the plugs on that engine, Kev.<br /><br />They only went to .030" with the availability of TC-W3 oil.<br /><br />I still recommend .040" for mostly trolling use.<br /><br />Good luck.

 

[Kev]

Re: Plug gap for trolling? - '58 7.5

Thanks, guys! That's very helpful info. I'll try out the wider gap and see how it works. I've got the old plugs as spares anyway. Just tuned-up the ignition system.