High Octane Fuels

[breamexplorer]

We have all argued the use ethenol blend fuels in boats but has any one used or using the 95 and 98 octane fuels. A mate and I out crabbing the other night in a 13footer 15hp (prob late 80's) running for the first time shell optimax 98, within 1/2 hour plugs fouled up, after a quick stop and clean it lasted about the same before fouling again, we put it down to the fuel, could this be the reason?, do older moters have to be tuned different to run this fuel?, would there be an advantage running this fuel (engine life) or is it better to stick with normal unleaded.
PS got some large crabs but upon checking all felt empty, they went back to fatten up.

[FNQCairns]

Yes the optimax is the culprit, no advantage to running it apart from the emotional benefit, believe it or not the higher octanes actually run too hot for 2 strokes not expressly built for them, oxygenates are used to in a sense artificially increase the rating and it is rubbery fuel science when viewed from all the applications a person could put the fuel into.

cheers fnq

[Kerry]

Yep the "feel good" feeling but that's about all!

[Spaniard_King]

I have been runing 95+ octane in my 130 honda I definately have better fuel economy(1453klm for 595litres) and the engine seems to run smoother. IMO the engines which run an oxygen sensor would best benefit from higher octane.

I use Shell V-max and Caltex something ... errrr ..it eludes me at present :P

Garry

[Roughasguts]

I wouldn't put High octane fuel in a premix, for some reason the higher octane or other solvents and cleaners, produces more carbon to build up under rings in the combustion chamber. With the four stroke around the valve seats, it's still early days to confirm this but some evidence is there after a strip down after long term use. By long term use, only 2 years and some failures are showing up, the fuel line might be cleaner and such it seems after combustion the problems build up.

Jury is still out for me at the moment so I stopped using Pulp, in every third tank, the motor did seem to run better though, but maybe it didn't all in me head.

[Spartan]

I was running 98% on mechanics recommendation (based on manufacturers advice) in a 1981 Johnson 100. The plugs kept fouling. After seeking advice in this site and the response by FNQ Cairns I switched to 92% and went from NGK plugs to Champion. So far so good, 2 months down the track, fouling reduced significantly and the motor runs fine. I can recommend the advice given by FNQ.

[PADDLES]

a 2s needs to run nice and hot to be running at it's cleanest and best. the higher octane fuel will run slightly cooler i think with the same ignition timing (as when using the standard unleaded). in any case dirt bike tuning gurus have been saying to avoid pre-mixing oil with optimax for years (or ever since it came out anyway) i'm surprised anyone's even bothered using it in a conventional 2s outboard.

[FNQCairns]

Whoo hoo! got one down the hole!!:) Thanks spartan.

Gut's what you say seems to be born out on the US websites from what I have read for long enough now that it is believable, sometimes even chronic coking of engines esp the 4 strokes on high octane fuels.

cheers fnq

[Dan5]

mate i have run premium unleaded in an efi 4 stroke out board for over 6 years never had any problems but i do use a quality filter and change it every 500 hrs or so

[Jabiru658]

A piece of information that isn't widely known is that BP 95 is actually refined to 95 octane rather than being brought up to the octane rating using ocatane boosters like the 98 and 100 ocatane fuels.

If (for whatever reason) one can't get standard ULP then you can normally use BP 95 (not sure about the makeup of mid octane fuels from other sellers though).

[Roughasguts]

Think in the past fuel was bought up to a octane rating using Heptane.
Does any one know what they use now.

[Kleyny]

I was told that Shell Optimax is for fuel injected motors.
something to do with spraying through injectors makes it mist easier.
BUT put it through a carbied motor especially boat or motor bike 2 stoke you will foul plugs like theres no tomorrow.
If you want to run the premium try the BP version (thats what i used to run in my Motor X bike) with great results.

I just use the 92 percent fuel in my 60 merc.

hope this helps

[Kerry]

....If (for whatever reason) one can't get standard ULP then you can normally use BP 95 (not sure about the makeup of mid octane fuels from other sellers though).

Many BP stations don't provide an option anymore! Choice is E10, E10, E10, E10, E10, E10, E10 or BP95 (1 pump), no standard ULP!

[FNQCairns]

Jabiru658 thanks for that, great info - found my fuel for the boat! Bloody well better not hold any sneaky drugs in it!! Say NO to drugs in fuel:)

cheers fnq

[breamexplorer]

Is what Kerry is saying a look into the future of fuels, a time when there is no choice but to use ethanol blended fuels (and there has been a lot said about it on here) or use the premium fuels, like the car industries some people will have no choice but to upgrade to newer outboards. Another thing that might help is the different sparkplugs, I noticed when my mate pulled the plugs they were the type with no electrode thing on the bottom just flat, could using normal plugs stop fouling so quick or is this what the other plugs were designed for.

[kind_cir]

Have been running PULP in me injected VN SS V8 for 8 years now and for over 200000km and It has never had a tune never had a fuel filter replaced and never had the plugs replaced in this time. It still runs perfectly and returns the same economy as it has always.
I have recently bought a 3.4m tinny with a 9.9 Evinrude of 91 vintage and run it on PULP and are on the third 25l tank now and have not had probs fouling plugs or running/ idleing rough, and it starts 1st -2nd go always. The plugs are of the exposed electrode type and have a light tan apperence on the electrode when pulled. I do run the boat at full noise most of the time and have not used it to troll as yet, but the Daughter has putted around at Idle for 20 min on occasions.
The thing gets up to 37kmh or 20knts messured using a hand held gps and I think this is a good top speed for what it is.
I will run standard ULP on the next few tanks, given all the advice on here not to run PULP in 2 strokes, and do some more testing to see if things improve or get worse.