Too much oil

[Fastjeff57]

Taken to the extreme--more oil than gas--one would end up with a low octane "fuel" that would cause severe pre-ignition. Going richer and richer approaches that condition, right?

Jeff

[Powerabout]

if we assume the oil doesn't add to combustion?

[champ20B]

Taken to the extreme--more oil than gas--one would end up with a low octane "fuel" that would cause severe pre-ignition. Going richer and richer approaches that condition, right?

Jeff

Thats a good question. I thought about that a long time ago myself. However, from my experience with various old outboards, I have never seen or heard of anything like this occur. I believe that this could happen if you go beyond a certain point. For example, one pint of oil in one gallon of gas is not going to affect its performance noticably, although that is 8:1... But if you mix it 4:1 or more, wierd stuff might start to take place. My brother and I have a 1997 model 35HP Johnson (3 Cylinder), on a 14ft center console boat. I removed the variable-ratio oil premix system and went to the old premix method a few years ago. We run it at 32:1 opposed to the 50:1 it requires. It runs absolutely perfect and has not had any fouling issues at all. Acceleration is very crisp and start-ups are immediate every time as we never had any trouble with it .

[Gene East]

I agree with Ron on oil mixture. I used to mix 2 qts. Mercury oil to 5 gal. of gas in my 20-H 50 years ago. Used plain old J-4-J plugs. Never had any fouling problems, certainly never burned any bearings, plus I won a race or two. Remember, most mechanics know more about the need to lubricate than anyone at the EPA. Never trust anyone from the government!

[Aeroliner]

In my old 20-H racing days the Mercury was run at 16:1 if I recall correctly. Back then we were running regular mineral oil and synthetics were only available quite some time later. If I remember correctly the oil was about 30 weight. Today in our racing program we run 10:1 in our C,D and E MOD Merc's using Castrol TCW-II which is a synthetic and also quite thin compared to the old Mercury oil. We also run magnetos on all our engines and champion J-4-J plugs without any issue of fouling. When looking at the fuel mixture I believe that the more oil used up to a point provides more power. This was found during our testing when we look at the GPS speed. The density of oil is greater then that of gasoline so in theory you get more BTU's per gallon with a heavier mix. When we look at octane rating we usually run 93 with no alcohol which is more then enough with the heavy oil mix to meet the compression requirements of our engines. For a time while the NBRA had a sponsor we were running fuels with alcohol in them with no issue also.

Alan

[omcstratos]

This is a little bit apples to oranges but anyway... When I was a lot younger, I had a 2 stroke weedeater type of motorized scooter. I messed around with that thing seeing what all it would do. I liked two stroke smoke and thought it would be cool if I ran it on straight 2 cycle oil. It smoked like crazy and had to keep the choke partially closed for it to idle. Other than the spark plug fouling pretty quickly and raw oil going through the exhaust, it seemed to run pretty well.

Also, before my time, one of our family's fishing motors was a mercury 10, I'd guess from the mid 50's. The motor was rated for 25:1 and I think that was because 2 cycle oil was really just a quart of motor oil. The oil doesn't mix as well with gas as tcw3 oils do so they had to up the ratio and that motor ran perfectly fine, Even outran our newer evinrude 18 later on.

Now after my rant, The main "thought" about mixing a heavy oil ratio would be lowering the octane rating in fuels right. Ok, then I would think that "back in the day outboard oil" mixed at 25:1 would lower the rating much more than tcw3 at 25:1 and those motors are still around.

[omcstratos]

This is a little bit apples to oranges but anyway... When I was a lot younger, I had a 2 stroke weedeater type of motorized scooter. I messed around with that thing seeing what all it would do. I liked two stroke smoke and thought it would be cool if I ran it on straight 2 cycle oil. It smoked like crazy and had to keep the choke partially closed for it to idle. Other than the spark plug fouling pretty quickly and raw oil going through the exhaust, it seemed to run pretty well.

Also, before my time, one of our family's fishing motors was a mercury 10, I'd guess from the mid 50's. The motor was rated for 25:1 and I think that was because 2 cycle oil was really just a quart of motor oil. The oil doesn't mix as well with gas as tcw3 oils do so they had to up the ratio and that motor ran perfectly fine, Even outran our newer evinrude 18 later on.

Now after my rant, The main "thought" about mixing a heavy oil ratio would be lowering the octane rating in fuels right. Ok, then I would think that "back in the day outboard oil" mixed at 25:1 would lower the rating much more than tcw3 at 25:1 and those motors are still around.

uhh, that might have been going off on a rabbit trail.

anyways, a lot of the production race motors are rated at 25:1 from the manufacturer. sst45, I think mercury 44xs, I think there was a study that from 50:1 it helps make more power as you increase to 18:1 due to sealing up the rings. More oil than that you begin to go backwards again.

[zul8tr]

uhh, that might have been going off on a rabbit trail.

anyways, a lot of the production race motors are rated at 25:1 from the manufacturer. sst45, I think mercury 44xs, I think there was a study that from 50:1 it helps make more power as you increase to 18:1 due to sealing up the rings. More oil than that you begin to go backwards again.

Lots of racers use more oil than 18:1 (like 8:1) and have fast running rigs. Right on the better sealing of the rings, and the bearings live longer at the higher revs.

[champ20B]

Thats a good question. I thought about that a long time ago myself. However, from my experience with various old outboards, I have never seen or heard of anything like this occur. I believe that this could happen if you go beyond a certain point. For example, one pint of oil in one gallon of gas is not going to affect its performance noticably, although that is 8:1... But if you mix it 4:1 or more, wierd stuff might start to take place. My brother and I have a 1997 model 35HP Johnson (3 Cylinder), on a 14ft center console boat. I removed the variable-ratio oil premix system and went to the old premix method a few years ago. We run it at 32:1 opposed to the 50:1 it requires. It runs absolutely perfect and has not had any fouling issues at all. Acceleration is very crisp and start-ups are immediate every time as we never had any trouble with it .

One thing I want to say about 2-cycle oil, is that you have to be mighty careful which oil you choose. I had a 3.5 Chrysler air cooled outboard (like a west bend type), that I ran 16:1 in. I used the ashless TCW3 junk. One day I was trolling in a bayou for speckled trout. Next thing, my bearings started squealing, then it siezed up. I also had a mishap, because of this, with my Evinrude 9.7 Lightfour. The rotary valve stopped sealing and it would not run right. It started spitting feul back out of the carburator. I mentioned this on another post, as to avoid the "clean type" oils. The way I tell a good oil from bad is simple. I smell it to see if it has a soapy/mothball type oder. If it does, I avoid it. If it has just a kerosene/oil odor, it 's probably good. Next I put a dab on the tip of my index finger and rub with pressure against my thumb. If I feel a slight bit of grip(traction) with a stop/go action of sliding my thumb and finger together, the oil has sorry lubricating quality. I avoid it. If there is only slippage with no traction, it is a good oil.