OK, once and for all, what's the real story here? I own three Johnsons, a '64 9.5HP, a '54 10HP, and a '56 15HP. The 9.5 came over 25 years ago with the owner's manual, so I know the mixture is supposed to be 50:1. I don't have that advantage with the other two. The decal is present on the 10, but the critical digit is missing. That's no help. No decals on the 15 at all.
I've had the 10 for roughly 20 years, and I always believed that the proper mixture was 24:1, 2 pints of oil in the 6-gallon tank. I've used it that way, and it still runs like a top - no internal engine problems that I can tell, though to be honest I only use it for about a week a year and it sits for the rest of the time. I use whatever 2-cycle oil I find that's cheapest, which lately has come by the gallon from a well-known discount chain founded by a man named Sam. The 15 is a more recent acquisition, which I converted to a one-hose system as I only had one two-hose tank. I use the same mixture as the 10 in that one, and so far, so good.
Just yesterday I downloaded a Johnson service manual from a link I found elsewhere on iboats, and I find that the OEM-recommended mixture for the 15, and presumably for the 10, is more like 16:1, or 3 pints to a 6-gallon tank. Hmmm.
I've read many threads on iboats, and there doesn't seem to be a consensus of what mixture should be used. I see some that use 16:1 in the older motors, some that use 24:1 in all three - even the '60s 9.5 - and some that use 50:1 in all of them. Even one or two that mix as I do. All claim no problems with long use, just as I've seen with my motors.
It's all quite confusing. Since I've had no problems, I'll probably continue to mix the gas as I have been. Unless, of course, somebody here comes up with a compelling reason to change. So tell me, am I courting disaster?
I've had the 10 for roughly 20 years, and I always believed that the proper mixture was 24:1, 2 pints of oil in the 6-gallon tank. I've used it that way, and it still runs like a top - no internal engine problems that I can tell, though to be honest I only use it for about a week a year and it sits for the rest of the time. I use whatever 2-cycle oil I find that's cheapest, which lately has come by the gallon from a well-known discount chain founded by a man named Sam. The 15 is a more recent acquisition, which I converted to a one-hose system as I only had one two-hose tank. I use the same mixture as the 10 in that one, and so far, so good.
Just yesterday I downloaded a Johnson service manual from a link I found elsewhere on iboats, and I find that the OEM-recommended mixture for the 15, and presumably for the 10, is more like 16:1, or 3 pints to a 6-gallon tank. Hmmm.
I've read many threads on iboats, and there doesn't seem to be a consensus of what mixture should be used. I see some that use 16:1 in the older motors, some that use 24:1 in all three - even the '60s 9.5 - and some that use 50:1 in all of them. Even one or two that mix as I do. All claim no problems with long use, just as I've seen with my motors.
It's all quite confusing. Since I've had no problems, I'll probably continue to mix the gas as I have been. Unless, of course, somebody here comes up with a compelling reason to change. So tell me, am I courting disaster?