Petrol type for old outboards

[andrew allan]

I'm just putting a 1970 115hp Evinrude on my old 18' Hartey Flareline, and there seems to be some debate on another forum about what type of petrol is best to use in these old outboards, which were originally made to use unleaded.

Some think that I'm better to use high octane fuel, and others don't see the point (and then there's the issue of ethanol as well).

?any thoughts

Thx Andrew Allan

[HaroldS]

If its got decent compression then use premium, low compression means you can get away with using regular. Ethanol is a con and your engine will not run as effectively on it as it will on straight petrol. Octane rating is a measure of the fuels resistance to detonation, it has nothing to do with power other than it it will operate better in a high compression engine an that's where you get the power.

[Chief Tiff]

This motor will be happy running on normal unleaded, don't bother wasting your money on premium as it wasn't designed for it.

Stay the hell away from any of the ethanol blends. Unless you use the motor every day the ethanol will separate out of the petrol and will absorb moisture. This is most noticeable in the fuel tank, but will also happen inside your carbs making the motor a pig to start. Ethanol doesn't mix that well with 2stroke oil either, especially when it has absorbed water! If you pre-mix the oil in the petrol tank then the ethanol can seperate out and you run the risk of engine damage due to lack of lubrication.

[DavidG]

Got a similar vintage Johnson 70hp
Runs on ulp at 50 to 1.
Found the best oil is the Johnson/evinrude one.
Expensive but does not foul plugs at troll speeds.

[BobR]

What is the feeling when ulp standard goes next year - premium?

[HaroldS]

What is the feeling when ulp standard goes next year - premium?

Sure, premium, there won't be any benefit to anything that doesn't need it nor will there be any benefit to your wallet.

[b.o.a.t.]

What is the feeling when ulp standard goes next year - premium?

G'day Bob
what's the story behind the question?
regards
AJ

[HOOKED.UP]

Hi Andrew.
From my own small experience and knowledge, I will not use standard unleaded fuel in any engine.
Especially older motors.

I have everything from a new Toyota Yaris, (this year), to a 1965 Johnson outboard. My work vehicle is a 1985 van and I have 2 ride on mowers, 1 new 1 is 30 years old. Several different outboards of various ages. Etc Etc.

NO WAY will I put unleaded in these engines.
They all perform better on Premium.

Mixed fuel with Premium is more reliable for a longer period, although I don't like keeping mixed fuels for very long anyway.

Another thing I do now on older motors is to run a spark plug, which is at least 1 heat grade hotter than originally specified.
This is just to help clean out the CxxP of unleaded fuel.

Ethanol is Metho.
It has it's uses. Great for picking up water in fuel systems.

Lousy burn temp.

Good oil, good maintenance and good fuel, are cheap insurance for the reliability of your motor.

Cheers.

Paul.

[BobR]

Hi AJ. Given that ULP is to go next year, my question was could I use premium grade on an old outboard without causing any problems. From Paul's response it would appear that there should be no problem.

[HOOKED.UP]

BobR.

Not only will you have no problems, but a "cheap" tune up is to go with the high octane fuel available from some service stations. I am not sure of the name of this fuel, but it is required by high performance engines.
We only have 1 available source in our area and that is over an hours drive from our country town, but every chance I get I will fill up with this high octane fuel and it really does clean up the motors. In the new car it gives better performance and improves economy to a noticeable degree.
You spend more at the pump, but save in the long term.

With the old engines and 2 strokes it is like a new lease of life, for the time it is in the tanks.
Any time you doubt your fuel, just check your spark plugs. They tell you what is going on in your engine.
A bit like a heart monitor. LOL.

Paul

[b.o.a.t.]

Sorry, I missed the news that "ULP is to go next year"

given that it is all ULP, do you mean that 91 octane is being withdrawn from sale, leaving just 95 & 98 octane?
Is this just a NSW thing? (Haven't heard anything about it here in SA - all our petrol comes from... elsewhere, since our local refinery closed.)
cheers
AJ

[Ted2]

Two stroke fuel of the 60's and 70's (including outboard fuel) was based on 'Standard' petrol of the day as opposed to 'Super'. Standard fuel had an octane rating of 92. So 91 ULP is sufficiently close enough as a replacement and is all that is recommended except for some modern two strokes such as on high performance motorcycles etc.

Using Premium ULP in an older design 2 stroke or any low compression motor is just asking to get misfiring, wet plugs, and other undesirable consequences.

The lower the octane rating of a fuel the more volatile it is, ie the less it can resist autoignition so it requires lower compression or it will ignite early.

The higher the compression ratio and the more advanced the timing and state of tune is the greater the reliance on higher octane rating fuel because it resists autoignition exponentially. Therefore the ignition system producing the spark to ignite the fuel also needs to be uprated. (read much heftier and more consistent spark).

In an old low compression engine which doesn't even have an advanced sparking system (at least one of the requirements to burn higher octane fuel) using premium 95-98 you will get sporadic misfiring or failure to detonate the fuel resulting in wet plugs which will exacerbate the problem of burning completely. You will also get less effective scavenging of the crankcase and ports (essential in a 2 stroke) and more unburnt fuel going out the exhaust. Ie you waste money, waste fuel, make less power (not more) cause more pollution and increase engine wear.

Putting a hotter range spark plug in will not solve all of the problems caused by inappropriate use of higher octane fuel but is evidence in of itself in trying to deal with increased plug fowling due to less consistent and complete burning.

[Jazzman]

What Ted2 said!

[A Duke]

Do not use any ethanol fuel with plastic or fibre glass tanks it dissolves some of them. You should see what strands of glass can do to an engine when they get ingested as the resin starts to dissolve and sets them free.
Regards

[Chris Parks]

The biggest issue with Ethanol is the fuel flow required, most two strokes will not have the jetting available to flow enough fuel, the motor leans out and then commits suicide. The reason for this is that the calorific value of the fuel is a lot lower than a normal unleaded. But and there is always a but, if you can supply enough fuel and get the ignition right you will get more power, usually a considerable amount more but this is even more so on forced induction motors. You can buy some very affordable after market programmable ignitions these days which I reckon would be a very good thing on an early outboard, far better spark output and you can custom build the advance curve which can only help.

The other issue with Ethanol (E85) is because the fuel flow is so high you need a BIG tank to supply the fuel, that is after you find somewhere to buy the stuff. A lot of guys in the performance car scene are using it due to the extra power it gives but the cost though lower to buy results in it not being cheaper. A big two stroke outboard would go nowhere on a normal tank, they use enough on normal fuel.

[BobL]

Do not use any ethanol fuel with plastic or fibre glass tanks it dissolves some of them. You should see what strands of glass can do to an engine when they get ingested as the resin starts to dissolve and sets them free.
Regards

Fibreglass I agree, but plastic I doubt it. Almost all whipper-snipper and chainsaws sold these days including the name brands have plastic tanks. If there was a any problem with this it would have shown up on international chainsaw forums especially in countries where ethanol has been used for some time. I have been a member of the international Arboriste site chainsaw forum (60,000 members, 1,400,000 posts) since 2007 and do not recall a single problem being reported about this. There are other issues reported using ethanol, or issues specific to plastic tanks cracking or splitting whether using ethanol or not.

[A Duke]

Hi Bob,
There are plastics and plastics, and he was asking about old motors. I am basing my info on experiences in the 1970s when I was in a country where they put 15% ethanol in the fuel to make it go farther. My brother in law did in his General Motors V6 Z drive and a lot of cars had plastic fuel lines and carburettor floats de-solve. The floats were rather interesting as older car had brass ones and some makes and new cars (of the time) had a plastic that was OK and they were available for the cars that were affected.
Might be something to keep in mind with Gerry cans now that we don't know who made them and what they have used.
Regards

[vk4]

Ethanol has a lower calorific potential than unleaded petrol and i would never consider using it in an outboard, (THE SEA IS UNFORGIVING)

I use Standard ulp for my +10Hp Tohatsu and it starts reliably every time and I get reasonable economy, I do believe that 95 octane would probably improve power slightly , but I doubt it would be enough to warrant the extra cost,.

Jeff