2 Stroke Exhaust...

[Jupiter_33]

Hi,

I got a question about 2 stroke outboard exhausts. I got a 09 Yamaha and just put it back together recently with new gaskets, prop shaft oil seals, bearing carrier O-rings, etc, etc. She starts with one pull and purrs nicely but I noticed that there is this dark brown liquid that comes out of the prop exhaust so I double checked the gear oil and it's still good and not mixing with any water. Everything is buttoned down good and tight and I tripled checked everything before sealing it all up. It is an older motor that hasn't ran in many years so I think that's probably a factor and I'm also assuming it's just the exhaust mixing with the water that's producing the dark fluid. One more thing to note is that I'm using the water muffs on the motor but I had the same results with the dark brown fluid when I put it into a large container of water to test. I'm wondering if this is just normal operation and maybe this is why 2 strokes are banned in many places Any thoughts would be appreciated, thanks so much.

 

[boscoe99]

Nature of the beast.

 

[Jupiter_33]

Nature of the beast.

Thx, puts my mind at ease, phew

 

[jimmbo]

There is a lot of Unburnt Gas and Oil that comes out in the Exhaust. Run the Motor in a Barrel for a bit and there will be plenty.
However, get a Latex or Nitrile Glove and get some of that brown Liquid on it and smell it. As bad as Gas and semi burnt Oil Smell, they smell like Roses compared to Gear Oil.

 

[909]

All 2 strokes want is to be ran wide open.
You'll also find less gunk if use a synthetic or semi synthetic oil.

 

[Jupiter_33]

There is a lot of Unburnt Gas and Oil that comes out in the Exhaust. Run the Motor in a Barrel for a bit and there will be plenty.
However, get a Latex or Nitrile Glove and get some of that brown Liquid on it and smell it. As bad as Gas and semi burnt Oil Smell, they smell like Roses compared to Gear Oil.

Thx for the info. I agree, I'd rather clean up gas/oil than smelly gear oil.

 

[Jupiter_33]

All 2 strokes want is to be ran wide open.
You'll also find less gunk if use a synthetic or semi synthetic oil.

Good tip, thx, I'll invest in some premium mixing oil.

 

[jimmbo]

Yamaha markets some very good Outboard Oil, as does Mercury. Smoke is the last thing I worry about, besides it helps keep the Mosquitoes at bay

 

[flyingscott]

I always get a laugh out of people saying 2 strks only want to run wide open. It is like people think, that a 2 strk outboards which were around a 100 yrs before 4 strks became mainstream can't run slow. I don't know if they think people did not troll before 4 strks came out or just weren't alive for the 2 strk hey day.

 

[jimmbo]

At least you knew the 2 stroke was running, and that it provided some protection from Insects. While it tended to Load up after a period of low rpm, a bit of revving in Neutral would clear it out, and provide even better Insect protection

 

[Jupiter_33]

Yamaha markets some very good Outboard Oil, as does Mercury. Smoke is the last thing I worry about, besides it helps keep the Mosquitoes at bay

I've heard good things about Quicksilver, highest reviews on Amazon I can find so I'll give that a try. The yammy oils also have high reviews but quite a few say it tends to smoke but I agree about the skeeters, especially where I live

 

[jimmbo]

Some Boaters cry about a little bit of Smoke, and newer 2 strokes, with Auto Mixing of Oil to gas, are at idle running on 150:1. I would love to see the Criers being near an outboard from the early 50s, those were run at 16:1 and 20:1. Actually, if they are still running today, almost all of them will still need to retain those Gas-Oil Ratios. A lot of older engines used Friction Bearings(Bushings) and the Oil acted as a Barrier to prevent Metal to Metal contact. Less Oil means less Cushioning, and that results in problem.

 

[99yam40]

Some Boaters cry about a little bit of Smoke, and newer 2 strokes, with Auto Mixing of Oil to gas, are at idle running on 150:1. I would love to see the Criers being near an outboard from the early 50s, those were run at 16:1 and 20:1. Actually, if they are still running today, almost all of them will still need to retain those Gas-Oil Ratios. A lot of older engines used Friction Bearings(Bushings) and the Oil acted as a Barrier to prevent Metal to Metal contact. Less Oil means less Cushioning, and that results in problem.

and they used plain old 30Wt motor oil

 

[jimmbo]

and they used plain old 30Wt motor oil

Which is higher Viscosity than Modern Oils, which start out at about SAE 20 and have thinners added.

 

[boscoe99]

Back in the day we put one quart of 30 weight motor oil into a six gallon tank. Filled up the tank. Mercury tower or power.

80 HP. Biggest motor they made at the time. No power trim. No gear shift. Start the motor in forward and off you went. Same for reverse. Best be heading the general direction one wanted to go when starting the motor.

Cable steering. Break a cable and you were as likely to go out of the boat than to stay in the boat.

Ah the good ole days. Folks don't know how good they got it today.

 

[jimmbo]

80 HP. Biggest motor they made at the time. No power trim. No gear shift. Start the motor in forward and off you went. Same for reverse. Best be heading the general direction one wanted to go when starting the motor.

That would have been a 1960 or 61 Dockbuster. Horrible/Dangerous design that made it into Production and then the Sales Floor.