4stk outboards- std or premium unleaded?

[Gaz_2000]

Thanks to the great advice I got on this site I have purchased a stacer bowrider (5.25M) with a 90hp Honda 4stk outboard.

The honda manual say's that it only needs 91octane fuel, i.e std unleaded.

What I am wondering is if there is any advantage to me in either fuel economy or power in running 98 octane fuel (optimax).

Thanks in advance.

[propdinger]

most outboard mechanics recomend that you DONT use optimax or the like as its not good for the motor which i cant really tell you why but 3 different mechanics told me not too so i dont
but in my car it works so gooood

someone will be able to tell you why you cant

cheers
jeff

[SNELLY]

Yes asked the same question when I got my 60hp Yammie and the mechanic said if you want to pour the extra dollars into your boat you can but you wont get any advantage.

Therefore no need and it would just be a waste of money

[duckbill]

As far as optimax is concerned, when I bought my motorbike I was told not to use optimax because it would burn too rich. Apparently cars can handle it with their more advanced engine management systems, but bikes can't. Must be the same for outboards. Again this was only for Shell Optimax, not other premium unleadeds...

[propdinger]

opps i use to run my bike on it and what you are saying sounds right duckbill as the motor is nearly the same as my outboard lucky i sold it

[casey]

fellas

Premium fuel is far more cleaner, burns better, and has a higher octane rating, all in all a better fuel. The use in outboards - motorbikes - mowers etc etc is again far better than standard. So for the extra cost it is up to the individual.
For me I use it in my outboard as its a fuel injected 4 stroke, and in my sons race motor bike 50cc 2 stroke.

[rodbender]

gday gaz-2000 as alan blake from blakes marine once told me if i wont to keep throwing good money away keep useing premiun fuel outboards donot need to run on it their is no advantage toit ur just throwing good money away rodbender

[Big_Kev]

My four stroke definetly seems to start better, but that is about it.
I only put in the premium if the boat has been sitting for a few weeks and has a half a tank of gas. I top it up with the premium as it is said fuel does go stale and I think that the premium will give the old stuff a boost.

[clutter]

If the manufacturer recommends normal unleaded that's what you should use, at least until the warranty runs out then you can do as you please. I think I would be inclined to listen to what an outboard technician says also, why ask advice from an expert and then do the opposite.

Cheers, Clutter

[Big_Muddie]

This is an interesting topic which always results in many opinions.

I changed over to Premium Unleaded (predominantly Caltex) about 6 months after I bought my 40Hp Yammie 4St. I did that after questioning the dealer - he sold me the motor and maintains the motor. His advice was that it will not harm the engine in any way, but he remained unconvinced that it had any specific benefit - that is, he didn't see any extra value for the higher price of the premium fuel.

So, after almost 18 months of exclusively using premium in my motor I have reached some conclusions, albeit without empirical data to substantiate them - just observation. The things that lead me to my conclusions are:

My motor is easier to start (as Kev has already stated). From dead cold, it starts every time on the second turn of the key. That is better than it was prior to changing to premium. Prior to that, it would take up to 4 attempts prior to starting. Once warm, it starts first time every time.

My fuel economy has improved. For instance, I was away for 5 days at the Pin last week (3/6 to 7/6) and clocked up 6 hrs running time on the motor (maybe a bit more but I'm being conservative). Some of that was in creeks, so it was quite slow, but the majority of the time it was running at 4500RPM (or a bit higher). I used 32 litres of fuel for that 6 hrs. This is typical of what I have been doing over these 5 day trips. If my memory serves me well, I had been using closer to 38 litres for similar hours prior to the change.

So, the conclusions that I draw are that my fuel economy has improved and the performance of the engine is better.

That's good enough for me and, as far as I'm concerned, justifies the additional cost!

Having said that, had the dealer told me not to use premium (and told me why), then I wouldn't be using it today.

As Clutter said, take the advice of the technicians - provided you have confidence in their ability - although they seem to have as many opinions about this issue as we do.

PS. The same holds true for performance of my car - significantly better fuel consumption when I use premium fuel.

[Kerry]

If it feels good, then do it but really if a motor doesn't require PULP then at least it feels good if nothing else.

Simply being a higher octane rating means nothing especially in low compression motors.

Make no mistake though, that PULP does burn differently (not necessarily better), at a higher temperature and actually burns at a differant rate.

Cheers, Kerry.