Question about oil/gas ratio with older motor

[fuzzyray]

I have an older Evinrude 15 HP motor (about 15 years old). It is rated 100:1 as far as gas:oil goes. I was told a while back that it might be better to mix it a little rich, maybe 75:1 because it is older. I was hoping if someone here (with a better knowledge of outboards) could let me know if there is any rational behind this theory. Any info would be appreciated!

[This message has been edited by fuzzyray (edited 05-19-2004).]

[ChuckN]

All my Johnson/Evinrudes I've owned from the 70's models on are 50:1

The real old outboards (prior to 1970ish) were 25:1 I believe. 100:1 is way lean!!

[This message has been edited by ChuckN (edited 05-19-2004).]

[fuzzyray]

Maybe I'm having a brain fart or something. I am going to recheck and make sure I know what I'm talking about, but I was pretty sure it was rated 100:1. Thanks for the reply though. I guess don't bother replying to this thread until I double check my motor, then I'll update this post tonight. Thanks.

[who are those guy]

general rule of thumb is that the older the motor, the richer the "manual" says to run the ratio. Reason is due to the oil quality over time has increased. You can run it a bit leaner with todays 2-cycle oil - wouldnt go much more then 50:1. Test it a little - if too much smoke and boggy - lean it up a bit - unless you want a mosquito screen

[Surface Tension]

For a short time in the 80's the ratio was 100:1 on some outboards. That is no longer recommended and 50:1 is what you should be mixing those outboards with.

[fuzzyray]

Thanks Surface Tension. I did a little more research and it looks like you are exactly right. My motor would be from the early/mid 80's and so I was correct in that mine is labeled on the motor as 100:1. Apparently there was some type of announcement in 1986 about running these motors at 50:1 from the manufacturer. I have been running the mixture at about 75:1 for the last few years and she has been running great. Just a little smoke from time to time but nothing unusual. I think I might mix my next tank at 50:1 and see if I notice a difference. I guess I would rather mix a little too rich than too lean. I would assume that mixing a little rich shouldn't cause any problems (except a little extra smoke perhaps). Thanks for all your input. I am just trying to get a better understanding my motor, it was handed down to me from my father a few years ago when my family moved to the state of Virginia (4 years ago). Good news is that they just moved back (my dad missed the fishing too much!) and they are now living in the Alexandria area. Lots of great new lakes to fish!!

[IFallsRon]

Running too rich can lead to gummed-up carbs and fouled plugs.

[fuzzyray]

So the general consensus is that it's best run at 50:1. I'll just keep an eye on the exhaust and check my plugs from time to time. Like I said, I have been running it at 75:1 for a few years with out any problems. How much of a difference do you think there could be between mixing 50:1 and 75:1?

[Uncle Grump]

Fuzzyray

I've got an early-mid 80's Envinrude as well, mine is a 30hp (twin). My fuel tank
has a oil compartment, which is seperate from the one for the gas. The tank is marked "100:1".

The oil is auto injected by the motor as needed. I talked to the service techs at the local dealership when I bought my boat (used, about 3-4 yrs ago), and they told me the 100:1 was in reality 50:1, that the 100:1 was simply to little oil, and the motors had been revised to inject at 50:1.

I have a little smoke appear at start-up due to a rich mixture (choked), but once it warms up, there is little. I would say that my snowmobiles smoke more at 50:1 than the outboard does.

UG

[fuzzyray]

Thanks Uncle Grump and everyone else for your info. I will be running at 50:1 from now on.

[This message has been edited by fuzzyray (edited 05-20-2004).]

[Wavey Davey]

It doesn't hurt a motor to mix rich, I was told by a marine mechanic to add a little extra oil to older motors.

[bbells]

It might be interesting to note that I changed over to synthetic 2 cycle oil on my pontoon boat. The HSOforum suggested 100/1 mix for my 50/1 engine. Well, I tried it, the engine din't run worth a darn, went back to 50/1. Another experiment that proves the value of following directions.