2 stroke mix

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DENBOY

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Hi, this is my first post on this forum so if I put stuff in the wrong place please be patient. Being new to boating this may be a daft question but can I use normal 2 stroke oil as used in scooters in my mercury classic 50 and is the 50 to 1 mix critical or is it better to go lean or rich. I have loads of basic type questions to follow.
Thanks Dennis
 
Welcome to the forum Denboy :)
I would avoid using scooter oil, as its generally designed for air cooled engines which run hotter than marine water cooled ones, i know when i used (when i couldn't get anything else) a cheep 2t oil in my yamaha 5 it ran very poorly. Especially since its a 50, so getting in to the high power end of things, you would be better to go for the proper mercury stuff, or have a look in the manual to see if it wants mineral or synthetic, then buy a marine version.
As for the mix, 50/1 seems quite rich anyway, most are 100/1, but if its what’s recommended, and the motor runs ok (50/1 will make it quite smoky), then i would leave it at that. My rule is add the correct amount (in my case 100/1), and then a dash more for luck, certainly you want to be a bit richer than a bit leaner.
Matt
 
Hi Dennis. You should use a marine two stroke oil as outboards tend to run at lower temperatures to scooters and such and it's designed for that.
50:1 is best. If too lean you risk damaging the bearings and overheating the pistons/rings.
If too rich it doesn't really matter except it'll smoke and run a bit rough at low revs.

(Before anyone corrects me, I'm talking about fuel/oil mix not fuel/air)
 
Not sure, i would think not, i know my seagul (air and water cooled, but predominantly air i think) overheats if i use yamaha synthetic, think its a temp thing, maybe a synthetic designed for air cooled engines would be ok.
 
is Synthetic outboard 2 stroke oil OK for Strimmers and chain saws
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No being air cooled they run much hotter than outboards which are mostly watercooled.
I'd be happier with air cooled engine oil in an outboard than outboard oil in a strimmer, chain saw etc. In fact many 2t oils sold for garden machinery are labelled as also suitable for small outboards.

The oil for modern outboards should be to TCW-3 specification although special oils may be called for for some high performance engines. Depending on brand you may have the option of a fully synthetic oil. (Your cal,l your wallet or the planet)

Since the mid 1960s most outboards (excepting again high performance racing engines and Seagulls of course) can be run on 50:1.


know my seagul (air and water cooled, but predominantly air i think
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I dont know where you got the idea that a Seagull is partly air cooled. Definitely water cooled, although the cylinder head may also be finned.
Seagulls before 1967 run on a 10:1 mix. Most produced between 1967 and 1978 can be converted to 25:1, Post 1978 they came ready to run on 25:1. A few of the later models were supposed to run on 50:1 but it is doubtful if any survived that ordeal.

Current recommendations are that even Seagulls should use a TCW 3 two stroke outboard oil.

Denboy ,

Welcome. You have posted in the right place.

Some outboards run on 100:1 but not the majority I think you will find, and then the commercial versions of the same engines are likely to use 50:1.

Do not use 100:1 in any engine for which 50:1 is specified and for longevity use 50:1 even if 100:1 is specified provided it causes no running problems.

Mix your oil as accurately as possible without going to extremes. I use a plastic conical laboratory measure to measure the oil but that is bordering on the extreme.
 
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Very grateful for the informative reply. I've been using outboard oil in the Stihls for a while so remember not to buy a chainsaw of me! They seem to be OK though.
 
One useful aid to getting the mix right is measuring out the oil quantity accurately. Older eyes can't easily read the vision window in oil bottles too easily anyway, but if you know how many litres of petrol you have bought the sums to calculate how much oil you need are simple. So......I ignore the bottle and instead I have a set of little stainless measuring cooks scoops from Tesco, costing around a fiver. They nest one inside the other, are clearly stamped with the quantity in millilitres, and make it sooooo easy to measure correct amounts of oil. With various outboards for both tenders (five actually, plus all the garden stuff, Stihl saw, Ryobi strimmer, Powercraft hedge cutter, Flymo mower etc all wanting different mixes it saves no end of muck-ups!
 
Use proper marine 2-stroke oil, you'll have endless starting problems with air-cooled oil.

As a last attempt to placate the green lobby, many late 2-strokes OBs recommended a 100:1 mix.

In practice it's best to stick to about 50:1 (as a read of all the handbooks will confirm).

Most of the small 2-T OBs were re-badged Tohatsu, they never changed from 50:1.
 
get the mixture right

agree about measuring the oil - my measures cost me a £1 butmake it easy to mix up a litre usinga measuring jug. Be careful though the mix actually affects the way the engine runs. Too much oil means the engine is actually running 'lean' with regard to petrol when it runs

usual ways of checking the petrol/air mixture is the colour of the pug. Putty colour-ish is okay, black is rich and wqhite is lean. Even on my seagull (i know wveryone hates them but mine does me okay!) once i got the carburrettor mixture right and th4e 25:1 oil mix the plug appeared putty-ish colour.

don't assume all two strokes leave you with black oily plugs
 
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