Choosing two stroke oil for outboard

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Mustardrat

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I am trying to decide which two stroke oil to buy for a 5HP Mariner outboard, and whether I should buy mineral oil, semi synthetic or fully synthetic. I am aware that the oil needs to be TCW3 spec, but all marine two stroke oil meets this spec, so it doesn't help to narrow down the choice.

Key factors (for me) are:-
- less smoke
- doesn't gum up the engine
- prolonging engine life, or at least, not destroying the engine prematurely
- not hazardous to the environment

There is Westway fully synthetic TCW3 oil on Ebay for £25.99 per 5 litres:
https://www.ebay.co.uk/itm/5-Litre-...129938?hash=item1a30475152:g:W9YAAOSwJq1ZZlHY
Has anyone used this oil, and is it any good? It certainly seems cheap for a fully synthetic oil.

At the other end of the price scale is Quicksilver Premium Plus, which is £48 for 4 litres. This is a semi synthetic oil, yet is nearly twice as expensive as the Westway fully synthetic oil.

What 2 stroke oil do you use in your small outboard, and how do you rate it?
 
Any TC-W3 certified oil should be suitable for your small engine but there is no need to buy the Premium Plus grade, Premium grade will be adequate

I usually use Quicksilver Premium in my 6hp Evinrude because it is readily available. The higher cost of an occasional 1 litre of Quicksilver from a chandlers is peanuts compared with the other costs of owning a boat.

At 50:1 fuel mix there should be virtually no smoke
 
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I was puzzled by original post as I just pick up the quicksilver stuff for my small outboard but given rate of usage never seems to run out and I did the query thoughts of OP here?
 
I have 2 outboards with very different requirements:
Tohatsu 9.8 runs well with very little smoke @ 50:1 = Quicksilver
Seagull Century Plus uses mineral oil @ 10:1 = any mineral based engine oil.
I'm sure we're all familiar with the sight and sound of these little workhorses.

Question:
I've been told that fully synthetic oil doesn't burn (as in lubricating 2 stroke engines) so how does it get used in outboards?
I thought the whole idea was to burn the oil/mix as part of the lubrication cycle, without which you'd have an exhaust full of unburnt oil - or am I mistaken?
 
Oletimer said:
Question:
I've been told that fully synthetic oil doesn't burn (as in lubricating 2 stroke engines) so how does it get used in outboards?
I thought the whole idea was to burn the oil/mix as part of the lubrication cycle, without which you'd have an exhaust full of unburnt oil - or am I mistaken?
Click to expand...

Synthetic oil does mechanically break down at a higher temperature than mineral oil but at combustion chamber temperatures all types of two-stroke oil will burn.

Richard
 
Mineral oils are hydrocarbons comprising a mixture of molecular weights, the heavier ones tending to form gummy deposits in high performance 4 stroke engines.
Synthetic oils are 'built' from gases and light liquids and thus the range of molecular weights is far narrower than in distilled oils. Otherwise they are the same thing, so will burn in a 2 stroke
 
vyv_cox said:
Mineral oils are hydrocarbons comprising a mixture of molecular weights, the heavier ones tending to form gummy deposits in high performance 4 stroke engines.
Synthetic oils are 'built' from gases and light liquids and thus the range of molecular weights is far narrower than in distilled oils. Otherwise they are the same thing, so will burn in a 2 stroke
Click to expand...

So, if I understand you correctly, I can switch 'Smokey Joe' onto a cleaner burning mix? But would it still need 10:1 or do you think that could be eased out to say 20:1 or less?
Cheers
George
 
RichardS said:
Synthetic oil does mechanically break down at a higher temperature than mineral oil but at combustion chamber temperatures all types of two-stroke oil will burn.

Richard
Click to expand...

Combustion chambers contain a big range of temperatures, the spark, the flame, the plug electrodes, piston and cylinder wall will all be different.
Better oil might well be changing less on the cylinder wall.

Unless you've got a 60HP outboard, the amount of oil is so small, might as well buy known good stuff.
 
Mustardrat said:
I am trying to decide which two stroke oil to buy for a 5HP Mariner outboard, and whether I should buy mineral oil, semi synthetic or fully synthetic. I am aware that the oil needs to be TCW3 spec, but all marine two stroke oil meets this spec, so it doesn't help to narrow down the choice.
Click to expand...

I am suspicious of the statement that the Westway oil in question is TC-W3®

It does not appear on NMMA's list of TC-W3® certified oils
 
Oletimer said:
So, if I understand you correctly, I can switch 'Smokey Joe' onto a cleaner burning mix? But would it still need 10:1 or do you think that could be eased out to say 20:1 or less?
Cheers
George
Click to expand...

That is probably true but even at 20:1, if that were possible, it might well smoke and would be pretty expensive. You could try with a semi-synthetic first.
 
Oletimer said:
So, if I understand you correctly, I can switch 'Smokey Joe' onto a cleaner burning mix? But would it still need 10:1 or do you think that could be eased out to say 20:1 or less?
Cheers
George
Click to expand...

You can modify a Seagull post 1967 to run on 25:1 fuel mix by changing the needle ( Villiers carb) or Jets ( Amal carb) and re-tuning. Not advisable for earlier engines due to different crankshaft bearings.
No mod required for Bing carbs
All engines post Jan 1978 use 25:1 anyway.

Full details on John Williams' "Saving old Seagulls" site. Needles / jets available from him too

EDIT
It will smoke much less on TC-W3 than it will on a mineral " engine oil" ........ The recommended oil nowadays is TC-W3
If it is of an age that can also be converted to a 25:1 mix there will be very little smoke .

Unburnt oil goes out with the exhaust gases, polluting the water
 
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It will depend largely on the age of your outboard.

Older powerheads (smokey Joe is ancient) were manufactured with wider tolerances on dimensions. Modern high power 2-stoke engines need synthetic oils to cling to the bearing surfaces and lubricate despite the higher temperatures and pressures. Mineral oil is perfect for older, engines. The seagulls were originally designed to run on SAE30 single grade engine oil; not even a proper 2-stroke oil.

My old Yamaha 4 ran on 30:1. My current Tohatsu 3.5 is happy with 50:1 neither was/is particularly smokey. I still use mineral oil in both. If I had a race tuned 2-stroke outboard I'd be using synthetics. I use less than a gallon of petroil a year.
 
Topcat47 said:
It will depend largely on the age of your outboard.

Older powerheads (smokey Joe is ancient) were manufactured with wider tolerances on dimensions. Modern high power 2-stoke engines need synthetic oils to cling to the bearing surfaces and lubricate despite the higher temperatures and pressures. Mineral oil is perfect for older, engines. The seagulls were originally designed to run on SAE30 single grade engine oil; not even a proper 2-stroke oil.

My old Yamaha 4 ran on 30:1. My current Tohatsu 3.5 is happy with 50:1 neither was/is particularly smokey. I still use mineral oil in both. If I had a race tuned 2-stroke outboard I'd be using synthetics. I use less than a gallon of petroil a year.
Click to expand...

That's interesting, my pair of Seagulls are '67 and'68 (I think), both done enough work to retire but both run as old Seagulls do, just keep plodding along. I've wandered for a while about possibly thinning down the oil ratio, but, accepting the blue smoke trail they go well. An old boy, who has quite a few years with these little motors, was quite adamant about the reliability of the mark being built in in the way they were designed to operate - he wouldn't listen to arguments for the designers simple lack of today's knowledge regarding oil spec or qualities. I'll look into what might be possible.
cheers
George
 
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If anyone wants to buy in bulk I buy Fuchs marine comp TCW3 oil from Opie Oils.
A box of 4 so 20L is around £95 delivered.
It's a good oil.
 
Oletimer said:
I have 2 outboards with very different requirements:
Tohatsu 9.8 runs well with very little smoke @ 50:1 = Quicksilver


Question:
I've been told that fully synthetic oil doesn't burn (as in lubricating 2 stroke engines) so how does it get used in outboards?
I thought the whole idea was to burn the oil/mix as part of the lubrication cycle, without which you'd have an exhaust full of unburnt oil - or am I mistaken?
Click to expand...

The burning of the oil is after its done its lub. function and that's only because its mixed with the petrol. You should not really run any older design of engine on modern synthetics. Hence the sale of classic oil for classic vehicles.
As an aside there are "wet sump" 2 strokes which don't burn the oil at all. (unless worn out)
 
Before the advent of "specialist" 2-stroke oils, 2-strokes relied upon the imperfect mixing of standard mineral oils and petrol and to ensure an adequate supply to bearing surfaces, excess oil was added to the petrol, 2T oils were developed to mix well with petrol and their better ability to be carried around the bearing surfaces allowed the petrol/oil ratio to be reduced, from 16:1 to 25:1 around the late 50's early 60's. A lot of engine development occurred between then and the 80's when synthetic and semi synthetic oils were introduced. Smaller manufacturing tolerances on bearing surfaces meant the the oils have to withstand higher bearing pressures while adhering the the bearing surfaces. Synthetrics have stronger long chain molecules than mineral oils but are also lighter. These properties are irrelevant to older design 2-strokes.
 
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