Outboard 2 stroke ratios

[CaptainCaveman]

Recently purchased a Mariner 4hp 2 stroke but what is the correct petrol/2 stroke mix ratio, I was told it is 100-1 is this correct? what ratio do you use and would I see an advantage in performace if for example I use a mix ratio of 100-1 rather than say 50-1?

Thanks
CC

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[mainshiptom]

I have the same engine !

I tend to put 100ml for every 5 liters.

100/5000=1/50

Tom

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[DavidJ]

Be very careful with this one. I have a 4hp Marina bought some 5/6 years ago which is 50:1 It is highly likely that they changed to 100:1 at some stage.
If you use 100:1 in a 50:1 machine it with seize
If you use 50:1 in a 100:1 machine you will get pre ignition and eventually damage the engine.
Suggest contacting the manufacturers with the seriel no.

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[CaptainCaveman]

Tom,

Do you use it on a 2.80 inflateable? mine is on a 2.80 Avon Rover I haven't used it yet (roll on the weekend)! how many knots would I expect? I have seen a few inflatables on our local stretch of river looks good fun

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[jhr]

I've got a 2hp Mariner and that's 50-1, so p'raps its a Mariner thang.

Try it out and see what colour smoke comes out; if little or none, then you've got it more or less right. I can't remember (tho' thousands will no doubt leap in at this point) but white smoke=not enough oil and grey/black smoke= too much, I think? (Flames = outboard b*&&ered).

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[jfm]

Davidj is right on. They used to be 50/1, now 100/1. You need to be precise about which motor it is. Post a pic maybe. If it is the Tohatsu 4hp that is bort by Merc and painted in mariner/mercury colours, and <5years old, then 100:1. If any doubt, use 50/1 till you're sure, as the 100/1 motor will run ok ish on 50/1

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[CaptainCaveman]

It is the one with a grey cover and brown/red/orange/bright orange stripes running horizontally it also has foward/neutral/reverse gears and the option for an external fuel tank...does this help? maybe I need to get in contact with mariner, is it british or an american manufacturer? or any ideas on where they are located?

 

[muchy_]

I used to have a Yamaha 20. I thought that the ratio was 50/1 but it ran like crap. Then I found out that it should be 100/1 and it ran brilliantly. So at the very least it makes a difference to the running of the engine even before you take into account that it will damage it.

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[DavidJ]

Mine (50:1) model has no option for external fuel tank but I wouldn't like to guess in conclusion that you have the later (100:1) model
I don't believe the smoke is the test, by the way, because it all comes out...The 50:1 will be smoky, run on both machines.

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[jfm]

That description doesn't prove it but if it has the external tank option and a valve on the port side that swings 90deg to select external tank then it sounds like the later 100:1 model. These run ok on 50:1 and the running in period requires that ratio, but they start much better on 100:1 becuase the petrol atomises better with less oil.

Mariner is part of Mercury, ie part of Brunswick based in USA, they own Sealine, Searay and loads of other boat firms. You cannot contact them directly AFAIK, too big. The importer is EPBarrus I think. There are lots of spoddy US forums that can tell you all you need on merc/mariner products, but I warn you, get your anorak on

Eg <A target="_blank" HREF=http://www.pfs-ware.com/kwast/disc_toc.htm>http://www.pfs-ware.com/kwast/disc_toc.htm</A>.



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[StephenW]

Think speed depends on the type of hull you have on your inflatable. If its a V shape you should get pretty good speed, if its flat then you'll get more drag = slower. The trim also has an effect so suggest you do not angle it.

We have a 3.5 hp Tohatsu and in a flat bottomed 2.5m inflatable ( with flat inflatable floor) we seem to get about 6-7 knots flat out. What seems to happen is that the boat will at slow speed push the bow through the water, at medium speed plane the bow a bit and at max. revs will dig the stern in at an angle (bring up the bow) but not really go much faster.

Suggest medium speed for fuel economy and sensible ride. Some weight in the bow seems to help a bit. My other half usually ends up sitting on the athwartships seat towards the bow facing backwards so she doesn't get a face full of spray!

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[Matthewb]

Not too sure on the Mariner 4 but the Merc 5 is 100:1. However, when I bought it I was advised to always run it at 50:1 but I can't find anything official from Mercury to support this advice.

Matt

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[chippie]

I remember reading on an american site that the 100:1 mix was introduced for environmental reasons , and that the preferred but unofficial ratio was still 50:1.

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[DavidJ]

I suspect that there have been some technology changes to allow 100:1 mixes. For example (maybe) needle roller small ends in the pistons against bushes previously.

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[jfm]

Not sure, but I think they always had needle rollers in big and little ends, as well as the crank bearings. At least on the decent makes like merc

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[mainshiptom]

You should get about 10 knots if you are pushing it but we normally just cruise at about 3-5 knots, we dont like water coming in.
Number one boy (10) loves it on its own but the engine is too poweful for him so he takes it easy.

Tom

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[andyball]

Think most 2-strokes had needle rollers for ages & ages. 100:1 been around since the 70's (or before?)so 'should' be perfectly reliable now given the right oil & suitable jetting.

Having said that, most pre-mix performance bike engines (motocross) use no more than 50:1 (I'm 10yrs out of date here,so things may have changed) & often manufacturers suggested 25:1 'tho' this smoked a lot.

Back to original question : I'd use 50:1, no power advantage of 100:1 unless engine is already jetted too weak(v.unlikely) & slight extra fuel of 100:1 mix will richen it up a bit.



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[ArthurWood]

I have a Mariner 3.3 and it's 50:1, normal 25:1 for very first use. ie running in.

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[duncan]

friend bought one (5hp 2stroke merc) a couple of weeks ago and I am reasonably sure that it was 25 - 1 running in going to 100 - 1

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[Matthewb]

Yeah, 25:1 running in and then 100:1 thereafter is right according to the manual - it's just the Merc dealer recommended 50:1 after the first tank run-in instead of 100:1. I am going to phone him and double check.

Matt



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