Petrol

[soapie]

Hello all,

Just curious to know what kinda fuel do most people put in the 2 stroke outboards?

I have been told that Premium can be abit too much for little motors, over-revving etc ? Any comments ???

Nick

[Wetpatch]

I personally used to use high octane on my old 25hp yamaha but was told not to use it on my new boat 75 hp and that was from the yamaha dealer at the show

[Guest Jocool]

Tohatsu said to NEVER use premium in their motors! Apparently the aromatics in it destroy seals and hoses???? So I only use regular.

[Guest Big-Banana]

Have a fishing magazine here that says Premium in any outboard is a big nono.

[Hooky.]

I put the basic unleaded fuel in my 25hp Suzi which is about an '85 model.

Mixed 50:1 which were the directions I was told by the boat joint where I got the motor from.

For an "old" motor it goes well and does the job with this fuel mix.

cheers

Hooky

[bullfrog]

If I haven't used the boat for a while I'll top the tank up with premium to give the old fuel a bit of a boost, but usually I use regular unleaded.

[Grozzo]

I ALWAYS use optimax or any other premium unleaded fuel in my boat... I have found that it runs alot better...

I have never heard or been told anything to think otherwise...

Does anyone have relevant document stuff to back it up or just what you were told to do???

Not having a go at anyone, just wondering thats all

cheers,

Wayne

[Ken A]

My motor is a 4 stroke & I was told I can run either but preferably premium.

I have been using premium for over 2 years with no problems.

Does anyone have relevant document stuff to back it up or just what you were told to do???

I would like to see that also. This subject comes up a bit & I can't remember ever seeing anything in black & white.

[Weasel]

I have a 40hp merc 2 / and was told to use premium at 50:1. Also never use old fuel. I dont know what you call old though. Unleaded is supposed to have a shelf life of only 28 days but old to me is about 3 months and I havent had a problem yet. (touch wood)

Weasel

Edited March 8, 2005 by Weasel

[David C]

i used premium for about 2 years now in my 40hp jonhson and no problems here just add a bit extra oil to the mix i think the premium burns a bit better and keeps the top end a bit cleaner ..i pull the plugs out now and then and no sign of carbon build up it looks great

Cheers Dave

[Blood Knot]

Have been told by one outboard mechanic to use premium as it would help engine idle & troll better (by better I mean obtain a more even & harmonius note). Have tried it and it seems better, but my 2 year old Mercury 75hp seems to vary its note to suit its mood, (must have bought a female). Like to here some expert opinion on Premium versus Standard ULP for the two's.

John

[Aero]

Two stokes will gain nothing from running premium unleaded.

Gererally two stroke outboards arnt tweeked to their fullest so are never working hard or on the edge of their limits.

Their timing advance is mechanical and will advance and retard acording to the throttle postion. So even if you were to run premium it wouldnt allow you to advance the timing to gain more performance. A car's timing will advance to the point of pinging and then slightly retard the timing, so a better fuel will allow a steeper timing curve before pinging occurs.

Chris

[Bashir]

I use unleaded. I've heard that premium burns too hot and you can do some damage or something along those lines.

[david]

Nick,

i was using unleaded on a 35 evinrude when we first brought the boat, and now i am using premium and it run's alot better than it use too.

Dave

[Grantm]

Its an interesting topic and one that can be debated for ever because there is so many different variations of fuel and different opinions and experiences.

One thing to note is any manufacturers recommendations are based on overseas fuel specs.When reading the specs check out the recommended octane rating and go with that, bearing in mind not all premium fuels in Australia are the same either.

For instance Shell Optimax is a 98 octane while Caltex Vortex Premiuim is only 95. Standard fuel is 92. Most owners books give a recommended octane rating.

My opinion is that premium wont hurt an outboard on its own but it may also be a waste of money in some cases.

Premium has a slower flash point therefore burns more complete in the chamber which in theory is why you can get more performance. The benefits of premium is more noticeable if you can advance the timing because of the slower burn cycle. This combo gives a much bigger 'bang'. I would be hesitant to do this in an outboard though as it would run hotter which in a car is ok, but an outboard may suffer.

Premium fuel has less additives in it, ie a wax type additive is put in standard fuel to stop it boiling in underground storage, this additive is not used in Premium. This additive is responsible for many fuel injector problems. Engines on premium dont have this fault, which is why premium is refered to as a 'cleaner' fuel.

Back to the question to use or not to use. My opinion is in an old carb 2 stroke model say over 15 year old outboards, it probably wont make any difference and is most likely a waste of money, dont forget these old motors were designed for super and rely on unused fuel to cool.

In an 2 stroke outboard on say less than 15 years old, carb type, it would probably stop the built up of crap on the carb jets which would help overall and may slighlty improve the idle, but without playing with timing the performance may not be noticeable, and you dont want to play with the timing as mentioned. Also because of the slower more complete burn, any cooling effects of the fuel will be gone, which may even harm some outboards.

In a fuel injected 2 stroke outboard I would say it would prevent fuel injector problems in the long term with a slight increase in performance based on the outboards ecu to 'relearn' the combustion stroke and would be ok.

4 strokes would benefit the most, with the greatest improvement being fuel injected four strokes for reasons mentioned. The fuel is only required for combustion and nothing else. No oil is mixed and no cooling required, so I would be happy with premium in these motors in theory unless the manufacturer says not to, thats the biggie - check your book. All newer models have clear instructions in the book on what to use so I would stick with that, although not many will recommend you use use the most expensive fuel, but it doesnt mean you cant. I have a brand new E-TEC and it states to use 92 octane (or standard) it does not say I cant use higher.

Dont forget that premium fuel is not a mirical cure for anything and wont fix outbords running faults nor will it give you dramatic improvement in power or economy.The effects of this fuel are mostly beneficial if used from day one.

Once again this stuff is only my opinion from my experiences in both industries, and if anyone thinks its wrong please feel free to correct it.

Hope this helps

Edited March 21, 2005 by Grantm

[Guest Jocool]

I have a brand new E-TEC

37669[/snapback]

Does that mean you got your new boat??? Have I missed a post about it???

[Grantm]

Does that mean you got your new boat??? Have I missed a post about it???

37705[/snapback]

Yeah took delivery of my new Stacer 4.6 runabout, Ill put a post up tonight with a pic.very happy.

[clutch]

For instance Shell Optimax is a 98 octane while Caltex Vortex Premiuim is only 95. Standard fuel is 92. Most owners books give a recommended octane rating.

I have a brand new E-TEC and it states to use 92 octane (or standard) it does not say I cant use higher.

Hope this helps

37669[/snapback]

Grant Ive bought fuel in the states for years and in the US regular was always 87-88 octane .................premium 92

It is always stated on the pump so you cant help but notice. Does that make Aussie regular US supreme?

[Grantm]

No. it just means they have different octane ratings. Premium fuel is still a better quality regardless of octane.There is more to Premium fuel than the octane rating. Its just that the octane rating has more effect on the way an engine runs which is why it is singled out and refered to.

Premium fuel over here means just that. Not only has it got a higher octane it is better quality, therefore it is premium. If premium fuel only had a 92 octane here there would be no question as to whether or not to use it, yes you would. But because our Premium is high octane you have to look at the effects of that.

That is why I suggest reading the specs in the book as to what recommended octane rating the fuel is, rather than whether the book says premium or not. If the yanks say put premium in without giving us the rating you would be using a higher octane than them, cause there premium is 92. Thats why they specify the rating.There is not just one answer to cover all types of engines because they are all built in different places and have different requirements.

Confusing ? ,yes. Is it easier to stick with standard ? yes.

I have to say there is a world of difference between the yanks and Aussie terminology and acceptable specs. It is my belief that Aussie comsumers expect a lot more from what they purchase than the yanks.We have excellent fuel over here. They have donkey piss.

The engines (cars) built for over here are built with tighter tolereances than the yank stuff. Look at Gen 3 Holden V8, the US spec stuff was shit until we fixed it in mid 2004, You fill there engines up with our premiuim and they couldnt handle it. We were fitting osize pistons on early gen 3 without boring out the cylinders !

Anyway my point is aussie fuel is high quality and even our standard stuff will work well in outboards for most applications.

Edited March 21, 2005 by Grantm