Would you buy a Two Stroke or a Four Stroke next time and why?

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woko said..

Jolene said..

AUS126 said..

Bundeenabuoy said..

AUS126 said..
I use to not worry about putting too much oil in the fuel, until I saw the unburnt oil come out the exhaust and leave an oil slick. I now realise how polluting 2 strokes are, and would happily put up with a heavier and more complicated outboard. I can see why we are moving on.

Are you saying that oill was running out of the exhaust?

Yes, unburnt oil goes out exhaust. I now tend to mix closer to 70 :1 instead of 50:1. I've been told you can get away with 100:1. Wouldn't want to have a warranty claim though.

You might be getting away without seizing the engine mixing oil ratio leaner but in reality your just wearing the motor out faster.

The fuel oil ratio is also affected by the the carby air mix, for instance to get more revs out of a two stroke you can lean it off ( we all know how they go like clappers as the fuel runs out, that's owing to the leaning of of fuel air mix ) but of course leaning the air fuel mix to get more revs means less lubricating oil for the engine, that is unless you increase the oil to fuel ratio to compensate.
Proably has no bearing on the average outboard, but I've used this method to squeeze more go out of every 2/ I've ever owned since I was put onto that theory in the pits at Liverpool speed way as a lad, and all of my bikes, mowers, brushcutters, chainsaws easily lasted as long if not longer that the the equivalent unit in other hands.
Golden rule- dedicated container, oil 1st ie: no oil in the container, no fuel in the container ever !

Whilst technically correct, a lean air/ fuel mixture has very little influence on lubricating the motor. A lean motor will fail from temperature rise long before lack of lubrication.
2 stroke carbureted motors usually run fuel rich on the idle circuit to 3/4 throttle , as they run out of fuel, they pass through the optimum fuel ratio at which point they develop the most power, then as the fuel runs out they go lean and stop.
A 2 stroke motor will tend to lean off as its held wide open for a period of time {like the straight on a race track) so by choosing that optimum mixture that gives the highest rpm at full throttle, your playing with fire, This is why power jet carbys (a jet that dumps extra fuel at wide open/ high rpm) are used on hp engines
The richer the fuel/air ratio along with the correct spark plug( to remove critical heat from the engine) the cooler the engine will run

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Jolene said..

woko said..

Jolene said..

AUS126 said..

Bundeenabuoy said..

AUS126 said..
I use to not worry about putting too much oil in the fuel, until I saw the unburnt oil come out the exhaust and leave an oil slick. I now realise how polluting 2 strokes are, and would happily put up with a heavier and more complicated outboard. I can see why we are moving on.

Are you saying that oill was running out of the exhaust?

Yes, unburnt oil goes out exhaust. I now tend to mix closer to 70 :1 instead of 50:1. I've been told you can get away with 100:1. Wouldn't want to have a warranty claim though.

You might be getting away without seizing the engine mixing oil ratio leaner but in reality your just wearing the motor out faster.

The fuel oil ratio is also affected by the the carby air mix, for instance to get more revs out of a two stroke you can lean it off ( we all know how they go like clappers as the fuel runs out, that's owing to the leaning of of fuel air mix ) but of course leaning the air fuel mix to get more revs means less lubricating oil for the engine, that is unless you increase the oil to fuel ratio to compensate.
Proably has no bearing on the average outboard, but I've used this method to squeeze more go out of every 2/ I've ever owned since I was put onto that theory in the pits at Liverpool speed way as a lad, and all of my bikes, mowers, brushcutters, chainsaws easily lasted as long if not longer that the the equivalent unit in other hands.
Golden rule- dedicated container, oil 1st ie: no oil in the container, no fuel in the container ever !

Whilst technically correct, a lean air/ fuel mixture has very little influence on lubricating the motor. A lean motor will fail from temperature rise long before lack of lubrication.
2 stroke carbureted motors usually run fuel rich on the idle circuit to 3/4 throttle , as they run out of fuel, they pass through the optimum fuel ratio at which point they develop the most power, then as the fuel runs out they go lean and stop.
A 2 stroke motor will tend to lean off as its held wide open for a period of time {like the straight on a race track) so by choosing that optimum mixture that gives the highest rpm at full throttle, your playing with fire, This is why power jet carbys (a jet that dumps extra fuel at wide open/ high rpm) are used on hp engines
The richer the fuel/air ratio along with the correct spark plug( to remove critical heat from the engine) the cooler the engine will run

Again an excellent discription ! You obviously know your 2/s very well and I was proably very lucky not to destroy the more domestic machines and as for bikes Thers a fair chance that I was off the edge of the track before they got a chance to blow up !

I was trying to find a 2 stroke to buy. they are illegal to sell from july. no new stock in oz, since last July.

we should see the great barrier reef replenish itself in no time with this new BS.

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Sectorsteve said..
I was trying to find a 2 stroke to buy. they are illegal to sell from july. no new stock in oz, since last July.

we should see the great barrier reef replenish itself in no time with this new BS.

6hp Johnson available in Nowra. Not mine and I don't know the condition but should get 20 years or so out of it.

Thanks fellas. I ended up with Gaels Johnson 8hp in exchange for 11east coast charts. The engine works Well . If You're reading cazou . Fair winds north. He did a very fine job in that Triton. New boat.
I took my 8hp mercury to a marine mechanic in ft George's basin. Kept it for 2 weeks and said. " I can't get it going. . "
I spent 450 on a new cdi unit too. I will try taking it elsewhere. Moby marine I reckon

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Sectorsteve said..
I was trying to find a 2 stroke to buy. they are illegal to sell from july. no new stock in oz, since last July.

we should see the great barrier reef replenish itself in no time with this new BS.

I believe that it is only new 2 stroke motors that are affected, second hand motors are still ok to sell.

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UncleBob said..

Sectorsteve said..
I was trying to find a 2 stroke to buy. they are illegal to sell from july. no new stock in oz, since last July.

we should see the great barrier reef replenish itself in no time with this new BS.

I believe that it is only new 2 stroke motors that are affected, second hand motors are still ok to sell.

The authoritative source for information on this:

www.environment.gov.au/protection/emissions-standards/outdoor-power-equipment-and-marine-engines

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Purfler said..

UncleBob said..

Sectorsteve said..
I was trying to find a 2 stroke to buy. they are illegal to sell from july. no new stock in oz, since last July.

we should see the great barrier reef replenish itself in no time with this new BS.

I believe that it is only new 2 stroke motors that are affected, second hand motors are still ok to sell.

The authoritative source for information on this:

www.environment.gov.au/protection/emissions-standards/outdoor-power-equipment-and-marine-engines

Thanks for the verification, not illegal to sell, just to import after 2020

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cazou34 said..

Sectorsteve said..
Thanks fellas. I ended up with Gaels Johnson 8hp in exchange for 11east coast charts. The engine works Well . If You're reading cazou . Fair winds north. He did a very fine job in that Triton. New boat.
I took my 8hp mercury to a marine mechanic in ft George's basin. Kept it for 2 weeks and said. " I can't get it going. . "
I spent 450 on a new cdi unit too. I will try taking it elsewhere. Moby marine I reckon

Good to know

I'm back in Australia and might be going up the coast soon too.
I worried that might happen !

Jolene, did you ever work on reed valve or rotary valve two stroke?
The scavenger type was and is the common one today but few knows the mistery of a Trabant motor or the MZ race engine any more.
It used to be fun tuning them.

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BlueMoon said..
Hi Jolene (or others) just trying to understand your post atthe top of this page more. You mention playing with fire if operating your 2stroke at full throttle, if I'm reading that right?
I always operate my 2 stroke garden equipment at full throttle, chainsaw, brushcutters, blowers etc. Then when turning them off, remove finger from throttle and turn them off straight away.
It has served me well in recent years and don't seem to choke up the exhausts this way.
Should i not be running the equipment at full throttle?
I obviously don't runthe 2 stroke out board wide open, but do give ita decent run occasionally.
Cheers

Hi Bluemoon.
There is nothing wrong with running a 2 stroke at full throttle if the fuel mixture is correct for the load the engine is carrying . If you tune the motor to run at specific load so that fuel mixture ideal, close to being lean and and max rpm, the motor should be fine,,, but if you increase the load and the time duration it stays at that load, the engine has a good possibility of going too lean and failing.

Examples of this would be a motocross bike tuned for motocross track where the throttle is mostly active around 1/2 to 3/4 throttle and only held pinned open for relatively short periods. This bike runs perfect on the track, However,,"Playing with fire" take the same bike to the beach or sand dunes where the soft sand or long straights of beach put a much higher load on the engine for longer durations. And you might be lucky to get 2km up the beach before you melt a hole through the piston. Rebuild the engine and now appropriately jet and tune the bike for high load of the beach and now the bike is unstoppable, you can ride it flat out all day.,,, but take it back to the mx track and you now find it lacking response, sluggish and your lap times are 5 sec slower.

Chainsaws and brush cutters are normally tuned to a point of max rpm and then the high speed screw is slightly opened a little more going rich, dropping the rpm slightly and creating a random miss in the firing. The over rich mixture now protects the engine for the normal load changes it encounters,, although with a change of cutter type on the brush cutter or bar and chain on the saw, the engine may require tune up attention ,
2 stroke glow engines are another type that require attention to tuning especially in model helicopters
2 stroke engines produce more heat, they fire every time the piston is at the top unlike a 4 stroke, This makes the fuel mixture more critical for cooling. If you have a look at an air cooled 2 stroke engine and an air cooled 4 stroke, the first thing you notice is the cooling fins on the barrel and the head are much larger on the 2 stroke.