More on seized Mariner 2.5

[VicS]

You have pulled the rug from under a long held belief of mine.

My logic assumed that at low revs not only was there less need for copious oiling due to the much lighter loading on all surfaces concerned but that a much smaller fraction of the oil is actually burnt thereby allowing more oil to remain for lubrication (and plug fouling).

I am also influnced by the way in which I understand variable rate oiling (in large engines admittedly) works. My understanding is that at idle speeds the oil injection rate is only equivalent to 100:1 or even 150:1 but increases to 50 :1 at high revs.

My theory seems to agree with what Andy Wilson said in his post immediately before your earlier one.

 

[srp]

50:1 = less petrol in the air/fuel mix = engine runs hotter = oil gets burnt = no lubrication.
100:1 = correct air/fuel ratio = engine runs at correct temp = oil does it's job.
If it says 100:1 in the handbook then use 100:1. Just because someone else uses 50:1 doesn't make it right, it usually just means they've got a different engine model.

 

[oldharry]

[ QUOTE ]
50:1 = less petrol in the air/fuel mix = engine runs hotter = oil gets burnt = no lubrication.
.

[/ QUOTE ]

I never yet had a 100:1 engine even begin to overheat with 50:1 lube, so its not a problem. The oil in the fuel is lubricating the bottom end of the engine - the crank, con rod and bores, then gets transferred to the combustion chamber where it is burnt off. IF the engine is running hotter and burning the oil off more efficiently, then this is nothing but a good thing: the exhaust gets less oil fouling, the plug runs cleaner, and less oil is discharged into the environment. Engine wear is also reduced, so it lasts longer. again good for the environment and your pocket!


50:1 rules OK AFIAC. As long as the 2% oil mix is allowing the engine to run clean, and not fouling the plug, then it can only be good for it to have better lubrication. Think of the 4stroke counterpart running in a bath of the stuff, and having it force fed to the bearings, yet its doing exactly the same job!

 

[m1taylor]

I have a 1959 Seagull which runs on 10:1 - starts beautifully, doesn't foul the plug and is now nearly 50 years old - so lots of oil can't be bad thing, altho' seagulls were explicitly designed to use a good bit of the oil to actually seal the crankcase.

 

[VicS]

Seagulls have plain bearings and no seals unlike modern engines which have ball races or needle rollers and seals. That's a big difference and is the reason they need a much oiler mix. Latter engines did use a 25:1 mix and it was possible to convert many of the older ones (those with a Villiers carb) to run on 25:1 simply by changing the carb needle. I did both of mine (a 40 Featherweight and a 40 Plus both dating from the early 1970s). It makes them a lot less messy to handle and less inclined to leave black oily deposits in the car boot. The alternative needles are no longer available though.

 

[oldharry]

[ QUOTE ]
I have a 1959 Seagull which runs on 10:1 - starts beautifully, doesn't foul the plug and is now nearly 50 years old - so lots of oil can't be bad thing,

[/ QUOTE ]

... except for the environment. Seagulls burnt very little of the oil, and could leave a visible oil slick on the water.

Scrap it and get something a bit more environmentally friendly /forums/images/graemlins/cool.gif

 

[Lakesailor]

Manufacturers don't always get it right. Johnson went from 50:1 to 100:1 and then back again on the same series of engines.
Using a smelly oily old Seagul may be more environmentally valid that buying a new lean running machine when you consider the carbon footprint of your new motor compared to the Seagull's footprint which has worn away long ago.

Course whether you can stand the noise pollution is another matter.

 

[VicS]

Re Seagull conversion to 25:1
[ QUOTE ]
The alternative needles are no longer available though.

[/ QUOTE ]
Wrong again! Ive just noticed that they are available again from John Williams via his Saving Old Seagulls website at £12.50

 

[oldharry]

[ QUOTE ]
Course whether you can stand the noise pollution is another matter.

[/ QUOTE ]
anybody know the maximum audible range of a seagull? - I reckon its around 1.25miles over water on a calm day /forums/images/graemlins/smirk.gif

 

[andy_wilson]

VRO does indeed work in that way.

The need for oil on the overrun in a marine engine is fairly minimal A car engine could run for miles down hill without any throttle on. Throttle back a marine engine and you return to idle and light load running within seconds.

There is a degree of coating goes on within a 2 stroke engine, otherwise most engines will be well and truly seized having been shut down and left in a damp locker for months on end. The roller bearings will run for ages without any lube at all, and even VRO engines will allow you to run them at reduced power with no oil being supplied at all, if you can stand the alarm goind off!

 

[andy_wilson]

I don't think running at 50:1 will mean the fuel air mix is so lean that the engine will overheat, after all, 2 stroke oil is designed to be burned away, with minimum ash and other deposits.