Hi Bob W — also happens to be my name. FWIW, friends and I in Michigan are all running 32:1 in all of our Johnsons and Evinrudes; 1956 Lark and Javelin 30hp, 1958 Lark 35hp, various smaller motors from 1956-58, Using TCW-3 spec oil. Less smoke and no lube-related problems in hundreds of hours at this ratio, and less oil in the lake too, of course.
I need help with a different issue. My 1958 7-1/2 Johnson, AD-12, has been hard to start for a couple of seasons, and began stalling when running at about shifting speed. It would stop suddenly, no signs of being rich or lean, no one-cylinder miss, just sudden death. And a rowboat ride home. I had rebuilt the carb (including a new float) when I got the motor a few years ago and it ran well until it started stranding me last year. Now it’s unusable.
I went through the carb again, everything looks as clean and beautiful as it did before. The sediment bowl and fuel bowl fill normally, inlet needle does not leak. But twenty pulls later, with choke on and throttle at start setting — she never popped once, and the plugs are completely dry. I took reed plate off, all looks good to me; but it’s as if fuel is not being drawn from bowl when cranking. But the motor runs fine, from idle to full throttle, when it does run. I’, looking through the carb again, hoping to find some clogged passage or something, but all looks great. Any ideas? I have started it with starting fluid a few times, after which it runs fine until it decides I need more rowing exercise. Argh.
Any advice appreciated,
Bob / Duralark
Hmmm. You mention it doesn’t seem to be dropping a cylinder, just stops. Perhaps it is dropping a cylinder, but you just can’t tell at that low RPM cuz it just stalls because it won’t run on one cylinder at that low throttle setting. When was the last time the ignition was serviced? Does it have relatively new/not original coils? It is easy to remove the flywheel inspection cover to have a quick look inside to see if the coils are cracked/failing. Try raising the throttle a bit more when starting cold, some of my 7.5s can be fussy this way also. I also discovered that the fuel in the tank/line gets fouled pretty quickly, so I always pump some fuel through the line/connector until I see clean fuel/oil mix before connecting the line to the engine.
The other thing I would recommend is draining/inspecting the gear lube. Water in the gear lube indicates trouble. This gearcase uses a shock absorber device in the driveshaft which likes to fail/expand, forcing the top of the driveshaft hard against the upper bushing/seal assembly. Sometimes this friction is enough to stop/slow the engine. Sometimes the upward movement of the driveshaft actually breaks the upper seal/housing casting allowing water to leak inside the gearcase. Raw water in the gear lube is usually a bad sign. And just because the gear lube is relatively clean, does not mean this condition can be ruled out. But, please don’t rip the gearcase apart on a “hunch” like this, unless there is raw water inside.
Needless to say, try to stick to the “basics”, like a compression test. Perhaps there is an internal engine problem, or the powerhead is just worn out. This engine absolutely requires a 16:1 fuel/oil mix because it uses “plain” crank pin bearings, not roller/needle bearings. Going light on the oil will wear the rods to the point when it might throw a rod through the side of the block. Perhaps there is some water in the fuel that is being sucked up filling the carb bowl. Perhaps the pressure tank system is not working properly and the engine is just running out of fuel. Just cuz there is fuel/oil mix visible in the glass bowl does not guarantee it is filling the carb bowl. Sometimes those stone type filters get plugged up and won’t pass fuel also, you could try running the engine with the filter removed.
Again, keep your diagnostic approach “simple”, 9 out of 10 problems are simple ones that get over looked in favor of more complex problems/diagnostics that just don’t exist.
