Re: Mysterious: Gap closes on spark plugs, '74 Johnson 115 hp
The continued saga:<br /><br />Yesterday I was tied up, so today after work I ran anxiously to the boat and did the following:<br />1. A cold compression test: 85-95-95-95. Used a high-quality, screw-in type guage.<br />2. Swapped in the old plugs that I had removed and saved for emergencies) 40-50 hours ago.Used a can of "Valve-Tect" aerosol decarbonizer, strictly according to the directions on the can: 5 minutes to warm up, about 10 minutes at real fast idle to spray in the whole can, soak 15 minutes, run 15 minutes at real fast idle to blow it all out. LOTS of smoke, diminishing to a normal amount. Altogether, about 30 minutes of fast-idle operation without any big bangs, knocks, or misses. <br />3. "Just 'cause," I did another compression test (warm this time, for what it's worth). Same readings, maybe 2 psi lower on each cylinder. Nuthin' noteworthy.<br />4. Rolled #1 piston (the cylinder that had previously had the closed-up plug) to TDC and inspected the crown through the plug hole. No signs of contact there that I could see.<br />5. Put my old plugs back in the locker for future emergencies (like dropping one overboard!!) and reinstalled the ones I had put in 20 hours ago (except #1, which got a brand new plug).<br />6. Fired it back up and ran the fuel out of the carbs, as always, and came home.<br /><br />No time for a "road test," 'cause the boat is 30 minutes up a no-wake canal and by now it's dark and time to go home and do daddy-type stuff. Will definitely run it hard this weekend and see if she goes or blows.<br /><br />Conclusions: not much. The 10 psi lower reading on #1 concerns me some. The general under-100 psi readings all around concern me some. But it runs like a top, idles nicely, and makes no heart-stopping clanking sounds. I spoke with the previous owner, the OMC tech who rebuilt it a couple of years ago, and he believed that if the wrist pin or big-end bearings were really in trouble to the point that the piston was contacting the plug, there's no way it would have run flawlessly for an hour without telltale noises or destruction. Does it sound like I'm trying to convince myself that there is no internal damage? OK, I'll admit it, I am. I really DON'T want to rebuild my first outboard this spring, out on my front porch (no garage). Even if I had the money, the time would be hard to find, and I've rebuilt enough otehr equipment to know that the learning curve on the first ANYTHING tends to be steep, treacherous, and painful.<br /><br />Between now and the time I run it this weekend, anybody have any further input to offer? Many thanks for all your postings, past AND future!<br /><br />Preston
