oil mixture ratio

shetland536

shetland536

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unsure what my oil mix ratio should be on my 1984/5 75hp mercury outboard.
its probably 100 or 50 to 1. in my first tank full i split the difference and have used 75 to 1.

any ideas?

cheers
lee
 
shetland536 said:
unsure what my oil mix ratio should be on my 1984/5 75hp mercury outboard.
its probably 100 or 50 to 1. in my first tank full i split the difference and have used 75 to 1.

any ideas?

cheers
lee
Click to expand...

As long as you don´t use so much that you get oiled-up plugs you are probably safer with more rather than less.
 
The ratio given originally relates to same time oil quality and spec.

Two stroke oils have come far since. Just remember to use oil specified for water cooled marine engines (TC-W3 which translates to 'TwoCycle-Watercooled generation 3').

Any major brand will do - no need to go for engine-manufacturer branded variety.
 
barrus recommended 50 to 1.

i was hoping they were going to say 100 to 1 as tick over played up a little bit on my last outing just as i put it into gear a couple of times it would cut out and was thinking i had put too much in at 75 to 1.


i will check the plugs to see what condition they are in.

i am using quicksilver premium which has tc-w3 recommendation.
 
shetland536 said:
barrus recommended 50 to 1.

i was hoping they were going to say 100 to 1 as tick over played up a little bit on my last outing just as i put it into gear a couple of times it would cut out and was thinking i had put too much in at 75 to 1.


i will check the plugs to see what condition they are in.

i am using quicksilver premium which has tc-w3 recommendation.
Click to expand...



+1 for 50:1 & Quicksilver premium ;)
 
When checking the parts list both 1984 and -85 are stated to have autoblend.

Most engines then were 50:1

In 1983 and earlier the 75 isn't present (70 hp is there).
 
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shetland536 said:
barrus recommended 50 to 1.

i was hoping they were going to say 100 to 1 as tick over played up a little bit on my last outing just as i put it into gear a couple of times it would cut out and was thinking i had put too much in at 75 to 1.


i will check the plugs to see what condition they are in.

i am using quicksilver premium which has tc-w3 recommendation.
Click to expand...

You should be able to down load an owners manual for your engine from The Brunswick Marine Download Center

Its not always easy to find the right manual .. probably best to read through the whole list of outboard manuals until you find the right one.

It almost ceratinly will be a 50:1 fuel mix unless it is fitted with an Autoblend system as already mentioned .
If it is an Autoblend model then gasoline with no added oil is used and the normal TCW3 2 stroke outboard oil goes in the oil tank.
Wise though to initally fill the fuel tank with 50:1 mixture and check that oil is being drawn from the oil tank.

The manual will enable you to identify the correct spark plugs and the correct gap
 
It WILL be 50:1, if you have auto blend, remove it. They kill more engines than anything else.

Idle mixture may be too rich or idle too low if it cuts out, but generally these engines can be quite temperamental by modern standards :)
 
..and if you do not want to remove an autoblend system you can fill both tank and autoblend reservoir with petrol/oil premix 50:1.

Then it won't matter if the autoblend works and there's no risc of getting extra oil added to the premix.
 
the mercury does not have autolube on it.


but i have a yamaha 20 on my dory which does--this does seems to be playing up as i have noticed that the little red warning light has come on on the front of the outboard. i was thinking of blocking off the autolube system but i couldnt find how to do it and wasnt sure what would happen with the sensors as i know that in the past when the oil tank went too low the engine went into "limp home"mode.
i hadnt thought of just chucking it straight into the tank and leaving the auto lube system with oil in.

thanks
 
Hi

a few things I disagree on

1: Marine oil is marine oil and we have found no better results from using any of them so get the cheapest you can and if you use the engine a lot then buy in bulk.
2: re the so called problems with 100:1. Sorry 100% disagree and we still service yams at this ratio weekly. At that age the biggest factor is how its been treated and have people skimped on silly things i.e. not changing gear box oil on a regular basis.

Oh and if I did have a choice of engine at that age my top 3 would be a: yam, b: yam, c: yam

3: auto mix is not the biggest killer of these engines.Sorry a service and repair centre this is not what we have found. There was a problem with Johnson VRO in the late 90's but that was a specific make and limited to a few sizes.

If you must turn it off, do it properly or get your local dealer to do it (less than £50.00) as you dont want to leave premixed fuel in the oil tank as it will go off.

Dave

ps nice boat why dont you look at the shetland boat owners forum if you need to know more about it or have questions or if you are a fisherman the world sea fishing forum is very good.
 
shetland 536 is just my user name that i am stuck with now--the boat went a few years ago now.
it was a great boat though and i do miss it.

i mainly use the dory but this year i picked up a picton 150 with the mercury 75 on..it was so cheap £50! i couldnt turn it down, it is an absolute corker in really nice condition and so fast but not really my thing so its probably going next spring. hopefully selling that and the yamaha 20 off the dory and treat myself to a more modern 30 or 40 hp for it.( maybe a yamaha!;-) )
 
2: re the so called problems with 100:1. Sorry 100% disagree and we still service yams at this ratio weekly. At that age the biggest factor is how its been treated and have people skimped on silly things i.e. not changing gear box oil on a regular basis.



and how often is that?
 
a lot of 2 strokes get scraped to due to the cost of a new/ refurbed gear box. if you can change 2-3 times per year but at least twice a year.

think of it as £10.00 well spent!

Its cheap and v easy to do and i will never understand why people ignore it.

We often put a magnet in the oil as it drains out and if there are bits in it we look closer. again v simple to do.

Dave
 
i have done the gearbox oil in both my outboards this year and the mercury seems to have some kind of stick which i presume is a magnet on the lower drain bolt.(which was clean.)
next time i take it out i will try sticking it to something just to see if it is magnetic.
 
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