View Full Version : 87 or 89 octane?
Riverbottoms
07-09-2002, 03:14 AM
Have a new 2 stroke 40 merc. which is better to use 87 or 89 octane?
Mine seems a little hard starting when it's cold using 87, would 89 help?
It starts fine once engine is warm on 87.
Thanks for all replys in advance.
For a few cents more, go to the 89. 87 seems to be highly contaminated and it loses octane level if she sits for awhile. Just my thoughts, Bo #582
Walizz 1
07-09-2002, 03:39 AM
Check the owners manual. If it says 87 that's what you use. Buy your gas at busy stations and it will be fresh.
Airwave(OH)
07-09-2002, 04:27 AM
The owners manual is the right way to go . It will most likely be 87 and that will be fine. 89 won't help the starting and could cause other problems.
In most cases, 89 will be an oxygenated product. You have to decide for yourself if you would be comfortable running it. Your owner’s manual will probably tell you 87 or higher. Myself, I always run the 91. It gives me better start-ups, better idling and seems to stay fresh longer than the 87.
I was told to use 89 in my Mercury 115
I was told by the dealer that it burns cleaner, causes less carbon build up and starts better
he said they can tell by looking at the spark plugs and inside of the motor during repairs which grade of gas was being used in the motor
I always buy the 89
rebs
I-Bob
07-09-2002, 07:29 AM
Know this is a dumb question but is 89 octane actually 87 octane with 10% alcohol added? Thanks in advance!
In most cases, 89 is 87 blended with 10%. At the pumps in MN, 87 will be 85 blended with 10%.
Bobby
07-09-2002, 10:13 AM
My owners manual for my new merc 90 2 stroke and
9.9 4 stroke both say to use the mid grade!
So I do!
Hawgeye
07-09-2002, 10:16 AM
My owners manual on my Merc 125 2001 states "not" to use any ethanol based fuel. In Minnesota, most 89 octane fuel has 10% added ethanol and I would not recommend to use that since it states that a build up will occurr and may cause problems. High octane however is approved as long as it is not alcohol based.
Agree with Hawgeye. My Mercury service manager says 'never' put 89 octane (ethanol) in my 2 stroke 75hp Merc!
Backwater Eddy
07-09-2002, 10:57 AM
Are all factory fuel systems ethanol safe?
Ethanol can deteriorate fuel lines that are not alcohol resistant, so I would wonder if that is a reasonable concern one should ask the dealer or a factory rep about?
On my older motors I have replaced all the original fuel lines with alcohol resident lines to be safe, you never know how much ethanol may be present in some mix's. Prior to doing so I found the older fuel lines were deteriorating internally from the new blends and causing plugged jets, screens, and filters.
Since I have replaced them I have had no fuel problems on any of my motors no matter what blend I run. I do try to run higher octane fuel whenever possible as it appears to burn cleaner as well as provide faster starts in colder weather.
Backwater Eddy...><sUMo>
I almost always run 87 in my 93 merc 60 2 stroke, mostly from advice I picked up here and from a dealer. I have started running 89 in it occasionally (my Jeep runs like crap on 87, and I ususally fill them at the same time), and my boat engine idles better and feels quicker, more responsive. I'm still not sure which one's reall better, but I use 87 most of the time to be on the safe side.
Eyez
87 octane gas with no ethanol or alcohol blended fuel for my motor per the owner's manual as well.
eye_guide
07-09-2002, 02:34 PM
I have a new yamaha and I had a new evinrude last summer. I have been told by more than one mechanic/dealer of each brand to stick with the 87 and put some additive in on occasion. I had to put 91 in the other since that was all they sold at the park and the engine idled alot rougher and smoked a little more than usual.
Both myself and all of my friends use only 92 octane. We have found that - day in and day out - the 92 octane gives more consistent performance, better shelf life, much better idling, and better starting.
I have talked to many of the resorts in northern mn, and nearly all of them - now sell only 92 octane gas. Perhaps one of the reasons is that they can get more money for it, but many of the IO/s to which they sell gas - absolutely won't run - unless it is on 92 octane. Since so many of the resorts really only have one gas tank - it is generally easier to cater to the folks with the biggest fuel tanks, and that is the i/os. Be default, then, we are using 92 octane, whenever we fill at any of these resorts, and have been very pleased with the results.
A few years ago, I was talking with my motor dealer, and he recommended the use of 92 octane. He recommended it - not for the octane, but for the additional detergent that he indicated was in the gas. I don't know if his comment is true, but I certainly know that my motor runs much better on 92 ocatne than other fuels.
take care
REW
David Anderson
07-09-2002, 03:22 PM
You may find this interesting
http://www.maxrules.com/fixgas.html