What octain fuel to run in a 1969 Merc 1000?

[OldMercsRule]

Hi guys. I know these are a dumb questions, but most of the advice I have seen regarding the grade of fuel to use in Mercs here on iboats is "mid grade". Trouble is: most of you run newer engines then I do.

I run two 1969 Merc 1000s and when I used to run a 1968 1250 I was told to run premium (93 octain), which I did but may have been expensive overkill.

I also run a 1981 115 and a 1979 115, and three 25 horse Mercs (1989 - 1996). The later engines should be fine with mid grade, (I would think), how about the old girls, (the 1969s 100 hps)?

Second related question: I know ARCO uses 10% alcohol here on the left coast. I use Chevron which does not have the same disclosure on the pump Arco has, (10% alcohol), and does not smell like alcohol like the Arco fuel does. Do all automotive fuels now use alcohol? I would like to avoid if possible. Thanks JR

 

[redjmp]

Re: What octain fuel to run in a 1969 Merc 1000?

I was under the impression that you should always use 87 in a two stroke.
All the other gases have additives that build up and foul plugs etc quicker.
The additives may increase octane but dilute the gas and actually rob power as well.
Also, If you have an older pre 80's motor, it has been posted on here that you should retard your WOT timing a few degrees. Today's gas is not as good as 60's or 70's was.
I don't own any newer motors, but I would follow the manufacturer's recomendations.

 

[Yepblaze]

Re: What octain fuel to run in a 1969 Merc 1000?

It depends on your confidence in knowing the engines max advance settings and how it is propped to your conditions.

There is one web forum where some guy swears the only gas to use if from the airport and with octane over 100.

I have, and have had a number of Mercury Motors from the late 50's through the 70's and they all run Arco regular with it's 10% alcohol at 50:1 with Pennzoil Premium semi synthetic without problems.

BUT!!! ............................

That is a very important BUT!!!..........

I maintain maximum spark advance well below the max allowed. Perhaps as low as the low end of recomended range, and make sure the motor(s) are propped near or towards the top of the sugested RPM range so as to not lug the motor.

If I need to load the boat with people and gear I might even switch props before I leave the house.

Also depending on each particular motor, and or boat combination, I may or may not consider extended WOT operation safe on a case by case basis.

I will do spark plug checks periodically, and make any fuel system repairs as soon as they might become evident.


Here in California, Gasoline must be oxygenated, and more so during certian times of the year. Since they outlawed MTBE that means alcohol. As time goes on they will probably put more alcohol into gas just due to political pressures. I've found that most of the old rubber fuel system components on my old stock have rotted away a long time ago, with or without the alcohol. And the new parts I get from Mercury seem fine with it.

 

[diaric]

Re: What octain fuel to run in a 1969 Merc 1000?

there's a couple of ways of looking at it. todays fuel is not of the same quality of the old fuels and don't hold up as well. the older moters were designed to run on the better fuels and most would do better on higher octane or as we call it premium. i have a 1966 merc 500 and have pretty much been running regular fuel. it sells faster, the tank turn over is faster and the premium has probably been there quite a while. I delivered fuel for a number of years and there is quite the difference in how fresh it is.

 

[OldMercsRule]

Re: What octain fuel to run in a 1969 Merc 1000?

I read all the available past advice about fuel grades for the old inlines and I conclude that: mid grade, (without alcohol: if possible) seems the least risky most cost effective fuel to use.

I just filled up my SUV at a fairly cheap Shell Station I found and it had the up to 10% ethanol disclusure sticker on the pump. The attendent did not have a clue. I will check with someone who delivers the stuff or regulates it. Chevron and Texaco do not have the disclosure stickers, and Arco, Union, Shell and BP do. The State of Washington is a little behind California but tends to follow their lead: unfortunately!!

I have tachometers on all my inlines and am always carefull to prop them right 5300 - 5500 @ WOT and not lug them.

The Merc 1000 I have owned and run for years has always run fine on premium in the past, but may also do fine on mid grade and the timing is backed off from the max setting. I will verify the setting of the timing on the Merc 1000 that is new to me and run mid grade in that one too. My 115 s are also retarded and should be OK with mid grade. I had to rebuild a 1976 1500, that the previous owner abused and I assume the detuned 115s should not run as quite as hot as the tweaked 1500 did. The 90 cu inch 100s should also be a little tamer then the higher hp inlines, (I assume).

Thanks for the advice, and feel free to correct me if you think I'm wrong in my assumptions herein. JR

 

[Scaaty]

Re: What octain fuel to run in a 1969 Merc 1000?

Well, most Merc gurus suggest 89. I have my 73 135 set at 20 1/2 degrees. I don't think ya need premium unless to run up to 23 degrees, but I would stick with no more than 21. If anyone worried about 89 going stale (which I have no concerns with), mix 1/2 87, 1/2 92

 

[OldMercsRule]

Re: What octain fuel to run in a 1969 Merc 1000?

Well, most Merc gurus suggest 89. I have my 73 135 set at 20 1/2 degrees. I don't think ya need premium unless to run up to 23 degrees, but I would stick with no more than 21. If anyone worried about 89 going stale (which I have no concerns with), mix 1/2 87, 1/2 92

Thanks Scaaty, I think I will go 20.5 too!! Mid grade is at or above 89 so I should be good, but 1/2 regular 1/2 premium would get me to the same place so I guess it depends on the price of the three grades. Since you live here in God's country, do you know if Chevron and Texaco dispense dinosaur fuel or does everybody have alcohol regardless of disclosure? Thanks JR ps: have ya been racin' arround in yer hot rod yet?? I would sure luv to see that lil' skiff flyin' @ 6000 rpms!!

 

[diaric]

Re: What octain fuel to run in a 1969 Merc 1000?

just so you know. when we loaded midgrade for delivery to a station. the terminal just gave you 50% premium then the other half regular. in most cases its not a seperate blend but a mixture of the two.

 

[emckelvy]

Re: What octain fuel to run in a 1969 Merc 1000?

Far as I know Chevron out here uses no alcohol. Been using it in all my gas-powered vehicles, boats, and yard tools for a long time, with never any fuel-related problems.

A good boating friend of mine has commuted quite a long distance every day for years and he said that he would consistently get better mpg on Costco gas than Chevron; so I'd expect Costco gas doesn't have alcohol either. Have never looked for a sticker however, the few times I've been there.

Used to run my old 2.8 Trooper on cheap Arco gasohol and it didn't seem to care, but then it was never that fussy. Don't think I'd run any Mercs on it though!!!

 

[redjmp]

Re: What octain fuel to run in a 1969 Merc 1000?

I stand corrected. Always been told to run "regular" but that used to be 89 octane. Now its not.
Here is some good reading:
http://www.brownsmarina.com/tech-preign.html
http://www.maxrules.com/fixgas.html
http://www.maxrules.com/fixfaq.html
http://www.outboardrepairs.com/topics/016011.html

 

[OldMercsRule]

Re: What octain fuel to run in a 1969 Merc 1000?

Thanks for all the input guys. It looks like mid grade is the minimum, n' one could make the case for 93 as well, after reading the above. I run Safeway gas in my SUV, (usually), if not: Chevron. I have never seen the alcohol disclosure on either of those pumps where it is displayed at Shell, Union, Arco, BP. I think Texaco, (which I also have run from time to time), does not have the disclosure either. I think I will contact the local oil co's to find out. JR

 

[Scaaty]

Re: What octain fuel to run in a 1969 Merc 1000?

Thanks Scaaty, I think I will go 20.5 too!! Mid grade is at or above 89 so I should be good, but 1/2 regular 1/2 premium would get me to the same place so I guess it depends on the price of the three grades. Since you live here in God's country, do you know if Chevron and Texaco dispense dinosaur fuel or does everybody have alcohol regardless of disclosure? Thanks JR ps: have ya been racin' arround in yer hot rod yet?? I would sure luv to see that lil' skiff flyin' @ 6000 rpms!!

I run Chevron 89 in the Merc (timing at 20 1/2, .080 jets). They also have a lock on "Techron", which is a great 'decarb" on the fly. Costco doesn't have midgrade, so you would have to mix. Not sure on the ethanol thing, as few seem to state it. Road trip back east last year had a 10% E-Gas pump at most places, but from what I have heard, up to 10% need not be disclosed...(don't get me started on the ethanol fiasco..saved very little, and put food cost up because of the price of corn for feed went up..more lost than gained..must be a government thing)
Needed a little downtime on the hot rod. Tossed a timing belt a week ago. Found out the ignition that looked good off the donor motor, was a mess inside. Trigger bearing was going south, cap fulla crap. New old stuff on again, have a total of 4 props to play with, so need a little time out on the water again...still need to get breakin hours on it

 

[OldMercsRule]

Re: What octain fuel to run in a 1969 Merc 1000?

I run Chevron 89 in the Merc (timing at 20 1/2, .080 jets). They also have a lock on "Techron", which is a great 'decarb" on the fly. Costco doesn't have midgrade, so you would have to mix. Not sure on the ethanol thing, as few seem to state it. Road trip back east last year had a 10% E-Gas pump at most places, but from what I have heard, up to 10% need not be disclosed...(don't get me started on the ethanol fiasco..saved very little, and put food cost up because of the price of corn for feed went up..more lost than gained..must be a government thing)
Needed a little downtime on the hot rod. Tossed a timing belt a week ago. Found out the ignition that looked good off the donor motor, was a mess inside. Trigger bearing was going south, cap fulla crap. New old stuff on again, have a total of 4 props to play with, so need a little time out on the water again...still need to get breakin hours on it

I have a 1971 1150 silverblock for parts, and it is in fairly good shape. If ya need the distributer or something, (other then the lower unit which: I want), let me know. JR

 

[redjmp]

Re: What octain fuel to run in a 1969 Merc 1000?

Taken from maxrules:
I have an older outboard with higher compression. Should I burn PREMIUM gas?
NO! here's why. The octane ratings are composed of 2 components, research octane and motor octane (RXM/2) divided by 2. The RESEARCH octane is the quality of the base stock, the MOTOR octane is derived from additives. The oil company will never tell you the ratios. Problem is the highest octanes are achieved by MOTOR octane additives, which will just gum up the pistons in a 2 cycle engine. Base stock is generally the same. The MID-GRADE gas has the detergent additives needed to clean your motor and sufficient octane for MOST motors. If you have a MERCURY, FORCE or OMC motor from the early 70's thru mid-80's refer to technical bulletins from the manufacturers for timing changes and replacement head gaskets to lower compression to use today's gasoline's.

 

[OldMercsRule]

Re: What octain fuel to run in a 1969 Merc 1000?

Thanks Redjmp, I'm going with mid grade after that last read, (or 1/2 premium 1/2 regular). I need to touch base with Chevron and Texaco locally to see if I'm right about the fact that they don't have alcohol. (I decarb my motors frequently to deal with carbon build up). Thanks again JR

 

[Clams Canino]

Re: What octain fuel to run in a 1969 Merc 1000?

Merc 1000 (any year)
Max advance = 34 degrees ; Fuel = mid-grade ; WOT RPM = 5200-5500 (change prop pitch to achieve such) ; Normaul use RPM = 4200

That's all. -W

 

[OldMercsRule]

Re: What octain fuel to run in a 1969 Merc 1000?

Merc 1000 (any year)
Max advance = 34 degrees ; Fuel = mid-grade ; WOT RPM = 5200-5500 (change prop pitch to achieve such) ; Normaul use RPM = 4200

That's all. -W

Thanks for the input. I shall follow your advice. BTW: Chevron in the State of Washington does not use alcohol in their fuel, (as I thought). I will contact Tex a little later and report back.

 

[diaric]

Re: What octain fuel to run in a 1969 Merc 1000?

was searching something else and came across this discussion. it starts off about rpm ratings for a johnson, but quickly changes to a discussion about octane ratings for fuel http://forums.iboats.com/showthread.php?t=180368&highlight=decarb

 

[OldMercsRule]

Re: What octain fuel to run in a 1969 Merc 1000?

was searching something else and came across this discussion. it starts off about rpm ratings for a johnson, but quickly changes to a discussion about octane ratings for fuel http://forums.iboats.com/showthread.php?t=180368&highlight=decarb

That was a good read thanks!! Texaco and Chevron seem to pump the same gas here in Washington. I did not contact anyone, (as I did with Chevron), but it is a fair assumption that Texaco does not have alcohol in their fuel here either. JR

 

[Yepblaze]

Re: What octain fuel to run in a 1969 Merc 1000?

I'm not trying to argue.


Just think about this............

Gas today, gone tomorrow.


Although your question related to octane,
(a specific scientific operational perameter),

any assumtion that what was gasoline yesterday,
(or dated remarks concerning it),

might be the same as what is available today, or tomorrow, can change without much fanfare or notice.