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  High Octane Gas or 'Premium' -- necessary?

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Author Topic:   High Octane Gas or 'Premium' -- necessary?
Morocco posted 02-27-2003 08:12 PM ET (US)   Profile for Morocco   Send Email to Morocco  
After much research and discussion with my mechanic, I can't figure out exactly where in the 87 -- 89 -- 91 octane range I should be.

My motors are Johnson 150 GTs, 1987 vintage.

Email to Johnson goes unanswered, and I don't have the original manuals.

The more general question is: with gas prices for premium topping out at over 2.25 a gallon (on the street, in the marina it is a LOT higher...)

Do you use premium?

Which engines REALLY need it?

How do you tell?

Dick posted 02-27-2003 08:28 PM ET (US)     Profile for Dick  Send Email to Dick     
All you need is 87 octane, with the higher ones all you are doing is burning extra money.

Dick

OutrageMan posted 02-27-2003 08:53 PM ET (US)     Profile for OutrageMan  Send Email to OutrageMan     
Some engines do require higher octane. The first one that comes to mind is the Darth Vader Mercury 300. Others are the I/O's in go-fasts. Your manual will tell you.

Brian

DaveS posted 02-27-2003 09:40 PM ET (US)     Profile for DaveS  Send Email to DaveS     
I wouldn't use premium unless it was specified in the manual. I recall an old post from a different board that discussed this same subject and it boiled down to the permium fuels burned at a higher temp and over the long haul cause damage to your engine. Anyone else out there hear about that?

Good luck.

DaveS

Sal DiMercurio posted 02-27-2003 10:24 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Back in 90 & 91 I blew 2 - Johnson 150s, one under warranty the other not, but omc made them both good.
They told me to run premium in my engine because the gas had changed, but that also changed when tcw3 oil came out.
Before tcw3 oil we had tcw2 [ blue oil ] but the oil wasen't able to lube the engine correctly & the added octane would help .
I burned primium for 2 years then tcw3 came, also no longer needing the 91 octane.
I recieved a letter from omc to go back to 87 octane & have been ever since.
I had a long talk with the omc rep for Calif before using 87 octane in my 2000 - 200 hp Evinrude FICHT, he told me the engine are designed to run on 87 period.
The only time you need the extra octane is if your running a racing engine or a big v-8 car or boat, & if it pings on regular, go up a notch till it stops.
Note, your 87 outboard wont ping..
The outboards are all designed [ except the racing engines ] to run on regular 87.
91 Octane is not a good idea for your older outboard, premium fuel burns slower, causing more heat & heat & aluminum engines do not mix, so stay with 87.
Sal
Sal
JBCornwell posted 02-27-2003 10:30 PM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
You need to refer to an owner's manual.

In some, including the manuals for my 9.9 Johnny 4 stroke and my Suzi DF70, it says to use 87 octane unleaded minimum, and recommends higher octane if available.

I understand that many manuals for 2 stroke engines say essentially the same thing.

I use 91 or better in both engines only so that I can use the leftover (there is always leftover with a 4 stroke) in my ML320.

If we were women, we would read the manuals first and listen to know-it-alls last. :))

Red sky at night. . .
JB

reelescape1 posted 02-28-2003 07:25 AM ET (US)     Profile for reelescape1  Send Email to reelescape1     
For the marina/dry-stack people here in Chas. SC, all that I know of only carry premium gas.
Bigshot posted 02-28-2003 09:25 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
There are about 20 posts here about this and there is no RIGHT answer unless your manual states so. What I always say is can you afford premium? If not then don't run it. In my Montauk I burn maybe $10 a weekend in gas, I think I can afford the extra $1 to run premium. My Baja I run 89 and my Mercedes i HAVE to run 91 min. If you had to run super, it would be stated somewhere on the engine, just like it is on my Mercedes dash, fuel fill, manual, etc. To play it safe, run good oil and 89 octane.
lhg posted 02-28-2003 04:16 PM ET (US)     Profile for lhg    
With the current TCW-3 and even higher rated oils, I don't think there is ANY brand of 2-stroke outboard, except the Mercury hi-performance/Racing models, that require anything other than 87 octane regular.

It always bugs me when I pull up to a marina and all they have is 93 octane. It's a forced profit center, and helps accomodate the go-fast and inboard guys. But for my 115's and 200 EFI's, it's a waste.

diveorfish posted 02-28-2003 06:19 PM ET (US)     Profile for diveorfish  Send Email to diveorfish     
For what its worth, I asked my outboard dealer (whose been in business for 75 years) what to burn in my Opti when I bought my boat last year. They expressly told me to burn 87 and not to use high octane it possible. They had a good reason but for the life of me I canít remember why.
NEVER SCARED posted 02-28-2003 08:48 PM ET (US)     Profile for NEVER SCARED    
I often add a few gallons of high octane to a tank of 2 month old 87 octane. Isnt octane lost over time? Any opinions?

Never scared

triblet posted 02-28-2003 09:17 PM ET (US)     Profile for triblet  Send Email to triblet     
2.25 for premium? It's up to 2.37 here
(Silicon Valley), and I hear in San Francisco
that's the price for regular.

Run what the manual says to run. Premium
burns slower than regular, and if your engine
is designed for regular, premium costs money,
gets you nothing, and may cost you a little
performance.

lhg, octane requirements and oil requirements
are unrelated. Octane prevents detonation,
oil prevents wear. TCW-3 isn't going to let
you run a lower octane gas.

Bigshot, my Evenrude 90 requires 89 octane
(according to the owner's manual), but it
doesn't say that anywhere on the engine, just
in the manual.


Chuck

lhg posted 03-02-2003 06:56 PM ET (US)     Profile for lhg    
Chuck - What I was getting at was that prior to TWC-3 oils, that have a de-carbonization component, there was an indication in the late 80's that low grade 87 was causing carbon build-up, and subsequent failure, in many 2-stroke engines. Accordingly, many were recommending use of higher octane. TWC-3 pretty much solved that problem, so 87 became useable again.
gss036 posted 03-05-2003 12:32 AM ET (US)     Profile for gss036  Send Email to gss036     
I just happened to be talking to my Merc mechanic today and asked about the rough idle on my 1989 200 Merc, carbed engine. He said to use premiun and it would smooth out.Idle mixture is injected at 100-1. I told him I only idled in no wake zone for about 5-10 minutes in and out of harbor and then run at 42-4400 rpm for 2-3 hours per trip. His reply was keep using regular gas and safe a few bucks if I could live with the rough idle. Sounds like good advise to me, since gas is starting to bounce around the $1.70-1.80 range around here.
gss036 posted 03-05-2003 01:11 AM ET (US)     Profile for gss036  Send Email to gss036     
I just happened to be talking to my Merc mechanic today and asked about the rough idle on my 1989 200 Merc, carbed engine. He said to use premiun and it would smooth out.Idle mixture is injected at 100-1. I told him I only idled in no wake zone for about 5-10 minutes in and out of harbor and then run at 42-4400 rpm for 2-3 hours per trip. His reply was keep using regular gas and safe a few bucks if I could live with the rough idle. Sounds like good advise to me, since gas is starting to bounce around the $1.70-1.80 range around here.
Sal DiMercurio posted 03-05-2003 01:25 AM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
A buck .75 $1.80, hell, buy it,..our 87 octane just hit $2.05 & thats not even Chevron.
I'm in North central calif. 35 miles east of San Francisco.
Sal
John W posted 03-06-2003 02:23 PM ET (US)     Profile for John W  Send Email to John W     
Gasoline degrades over time, and what was 87 when you bought it may be lower after a 2 month lay-up. Also, the anti-carbon additives the gasoline companies add (Chevron's "techron", etc) are in larger doses in the higher octane versions than they are in 87. If you put additives in your fuel (PRI-G, the Yamaha anti-carbon stuff, etc.), and you go through gas quickly, 87 is fine I'm sure...after all, the manuals say so. But if you don't, the extra additives in hi-test, and the fact that gas will degrade over time, are reasons to but higher octane IMO.

It may be true that theoretically the higher octane may burn hotter. And unless your motor is tuned for it, the higher octane won't give much of a performance benefit. But I don't believe that running 91 or 93 octane will cause a motor harm. I've used hi test for 20 years and have never had it cause a problem. I've had a couple of mechanics reccommend running at least 89 in outboards, for the reasons above. That doesn't make it right, but I don't believe running hi-test will cause any harm.

SaintGeorge posted 03-06-2003 06:05 PM ET (US)     Profile for SaintGeorge  Send Email to SaintGeorge     
Indeed there are some Johnson V6 outboards that require higher octane fuel.
I do not know if your's is one of them.

But do not assume that it is just a waste.

Some Johnson V6 motors have high compression heads; and combined with an advanced spark, they could require high-octane. Otherwise you risk burned pistons, and/or broken rings due to pre-ignition. The only way to know is from the engine documentation.

By the way, in some cases there were OMC service bulletins explaining how to de-tune the engine (usually retarded spark) to deal with fuel quality for the high-output engines.

If you can't get an answer from Bombardier, try seeing if some one at Ken Cook company will look it up in the manual (they support older OMC with ORIGINAL documentation.

jp

Swellmonster posted 06-23-2003 05:19 PM ET (US)     Profile for Swellmonster  Send Email to Swellmonster     
My 99 225 efi manual says to use 89.
Another question.......
When buying gas on the water, what octane are in those pumps?
I usually see 89 to 93.. never 87
cape_rover posted 06-23-2003 08:51 PM ET (US)     Profile for cape_rover  Send Email to cape_rover     
If your 2 stroke motor was pinging would you hear it? You wouldn't because of the engine noise, the wind, the water, etc. That is why you should consider using premium gas.

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