Gasoline,,,?

[1960 Sears 1438]

Im new to the site,,and new to outboard motors,,Im in process of fixin up a 1960 sears 14 ft. and bought a 1975 9.9 Evinrude for it. . And I'm curious on what grade of gas to run in it,,,and what I might use as an additive if need be running ethanol gas. I do have access to leaded gas just cost me 6 bucks a gallon :shock: when I buy it for my truck lol. Well thanks for any info,,,,,,,,Robert

 

[bassboy1]

No need for leaded gas. The benefit of it is for older engines, with softer valve seats. The lead additive in the fuel provides a "cushion" if you will. On a 2 stroke, no matter the age, the lead is absolutely worthless, as 2 strokes don't have valves.

Run standard 87. On the older motors, higher octane won't get you anything, and the factory often recommends against such. With this ethanol crap we are getting, a regular usage of Stabil for ethanol (blue stuff, I believe) is great, as the ethanol just loves to get every molecule of water possible into your fuel. Furthermore, it eats away at the fuel hoses, as in 1975, Evinrude had no clue that fuel mixed with ethanol would be run in it, so provisions to make ethanol impervious hoses were nonexistent. If you're real concerned about it, a fuel/water separator would be a good investment, but I don't run one on any of my smaller motors. If I had a newer (read costlier, and also read less durable) motor, I would certainly be running one, but the old twin cylinder J/E's are simple and bulletproof enough that it doesn't affect them near as much as a new one. Plus, for what they cost, it just isn't a worthy investment, IMHO.

 

[1960 Sears 1438]

Thanks a bunch ---- I'll just be running the 87 then,,,,,now on the Sta-Bil ---how often you recommend I put it in the gas,,every tank fill up with the the oil? THANKS AGAIN---Robert

 

[lckstckn2smknbrls]

I run Seafoam most of the boating season and Startron for the winter. You will also find me putting Sta-bil in the tank.

 

[1960 Sears 1438]

thanks ,,,but is that for EVERY fill up ?---Robert

 

[lckstckn2smknbrls]

I will use more seafoam in the early part of the boating season.

 

[MeanMouth]

No need for leaded gas. The benefit of it is for older engines, with softer valve seats. The lead additive in the fuel provides a "cushion" if you will. On a 2 stroke, no matter the age, the lead is absolutely worthless, as 2 strokes don't have valves.

Run standard 87. On the older motors, higher octane won't get you anything, and the factory often recommends against such. With this ethanol crap we are getting, a regular usage of Stabil for ethanol (blue stuff, I believe) is great, as the ethanol just loves to get every molecule of water possible into your fuel. Furthermore, it eats away at the fuel hoses, as in 1975, Evinrude had no clue that fuel mixed with ethanol would be run in it, so provisions to make ethanol impervious hoses were nonexistent. If you're real concerned about it, a fuel/water separator would be a good investment, but I don't run one on any of my smaller motors. If I had a newer (read costlier, and also read less durable) motor, I would certainly be running one, but the old twin cylinder J/E's are simple and bulletproof enough that it doesn't affect them near as much as a new one. Plus, for what they cost, it just isn't a worthy investment, IMHO.

I've always ran 87 too, but the ironic thing is, I read my 1976 Johnson manual that Jim provided me, and it says to use nothing but 90. First time I had seen or heard to run premium. I'll quote it from the manual here, which are Johnson/Evinrudes 1965-1978:

"The only fuels recommended for outboard, 2-stroke motors, are marine, automotive white, gasolines of 90 octane or greater."

 

[bassboy1]

Hadn't heard that before. I've got a manual here that states run the lower grade. Then again, at one point, all the manuals for the late '80s Johnnyrudes also said use 100:1 fuel/oil mix, which they later changed and backdated all under those years to 50:1. I do know that the higher octane (thinker higher alcohol content), fuels can actually do more harm than good in older outboards. I know of people with newer EFI outboards that have actually doubled their mileage by using 91, but I certainly wouldn't do it on a carbed motor.

 

[perchin]

This octane thing must just be with outboards then, cuz my snowmobiles and motorcross bikes have always needed the premium. And they are both 2 strokes, and both run better on the prem.

 

[KMixson]

I have a 1975 Evinrude 9.9 and it runs fine on 87 octane mixed 50:1.

 

[perchin]

Well its all good to know I guess.... but I've always just run 87 mixed 50:1 in all my outboard motors. Never run any stabil, but if it benefits me I guess I'll start. I run a Merc. 110 9.8 hp and a 125hp Force on the pleasure boat. Is this also needed on the Force motor?

 

[MeanMouth]

Well its all good to know I guess.... but I've always just run 87 mixed 50:1 in all my outboard motors. Never run any stabil, but if it benefits me I guess I'll start. I run a Merc. 110 9.8 hp and a 125hp Force on the pleasure boat. Is this also needed on the Force motor?

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Like you Perchin, my family has always run 87 without any performance problem whatsoever, and have never used a treatment additive. We have a 1976 15hp and a 1968 20hp, both still run great off 87 without additives.

I would say keep doing what you're doing, and just keep up with the maintenance. Looks like you've got everything under control already, so I'd stay with it. If it ain't broke... :wink:

 

[crazymanme2]

I don't run any additives either & no problems.

 

[1960 Sears 1438]

----seems like Ill just have to try and find out which one preforms the best,,since there seems to be abit of both high grade and reg. unleaded answers ,, thanks for all your responses,,,,Robert

 

[WaltR]

Octane is always an interesting and counterintuitive subject much like motor oil, but I'll leave that for another time.

The higher the octane number, the more compression the fuel can withstand before detonating (igniting) by compression alone (pre-ignition, knock, pinging). In broad terms, fuels with a higher octane rating are used in high performance gasoline engines that require higher compression ratios. Octane ratings are not indicators of the energy content of fuels. They are only a measure of the fuel's tendency to burn in a controlled manner, rather than exploding in an uncontrolled manner. Where the octane number is raised by blending in ethanol, energy content per volume is reduced. Ethanol BTUs can be compared with gasoline BTUs in heat of combustion tables. (https://en.wikipedia.org/wiki/Octane_rating).

An engine definitely derives no benefit from higher octane than an it requires. I'm not sure what of the many Octane rating system was being referred to by OMC back in the day (there are, and have been a few, and the manual refers to white gas heavens sake). In states other than Missouri and Montana, where alcohol free premium is available, you'll get less energy out of each gallon of gas, since alcohol is the main octane booster in most gasoline and alcohol has a lower energy density than gasoline (Ask anyone that's filled up on E85 gasoline and the lousy mileage they got). Alcohol is generally not nice to engines that weren't made to use it, like vintage outboards as it a solvent that eats rubber for example (hmm, replace float, carb and intake gaskets, fuel lines...), so less is generally better (My current cars have a circle with a line through E-15 and E-85 inside the gas door.). As a rule, a simple gasoline engine will perform the best on the lowest Octane gas that doesn't cause pre-ignition (knocking/pinging), but if you can get Ethanol free fuel, definitely go with premium in Missouri or Montana.

You can achieve better performance with high octane gas if your engine is designed for it. Thermal efficiency increases with cylinder compression ratio, which is why increasing it was one of the tricks in hot rodding. Many modern engines can make do with regular and if designed to take advantage of it, can produce more power with premium because they can vary the compression ratio and ignition timing to make the most of a given Octane. My '06 Highlander Hybrid with variable valve and ignition timing could crank up the compression and advance the timing to get an extra 5 hp out of premium. A whopping 1% I believe. I do recall that there were rare cases when the price differential between premium and regular made for break even at the pump because that translated into a 5% increase in fuel economy. My Prius on the other hand lost about 5% in fuel economy and ran poorly if I accidentally gave it a tank of premium.

The legal threshold for premium in the US is 91 octane, that puts the 90 octane recommendation of old in the regular gas range. Unless your in Missouri or Montana higher octane means more alcohol and it's downsides.

I think with our vintage outboards a bit of field testing might be in order. I'm also sure that our old engines are quite far from factory spec by this time.

I just got my '65 18 hp Johnson Seahorse running. It seems to run fine on 87 Octane gas in the tank. If it's pinging, I wouldn't know it because I never heard it run until last week and it's my first two stroke engine that's not a chainsaw or weed whacker. I certainly can afford premium gas for the amount of fuel I'll use, especially on 20 cents off Thursdays at Shell. I might just run a gallon of each and see how she likes it. Unfortunately I have little control over other variables, so anything that isn't grossly obvious will be meaningless. I not about to run through two gallons of gas in the test tank. I'd certainly expect the premium to go bad faster from the higher alcohol content here in Delaware. I'll report back if I find anything useful. :mrgreen:

 

[wmk0002]

I have access to a couple of gas stations near my lake and which sell ethanol free gas. I run my boat with a 70 hp with the lower grade due to a larger tank and for cost savings. For my 9.9/15 hps I use premium because the extra cost for 3 gallons is negligible to me. I haven't really noticed a difference in octane rating for my outboards although, the 91 octane MAY idle a little better. I also have a 4 stroke dirt bike with a high compression piston and can definitely vouch for its need for premium fuel though. Anything less, and it throttle response is slowed dramatically and it idles terribly as well.

As for additives, I always add Seafoam at a rate of maybe 1 oz/gal of fuel. I'd like to believe it helps keep the carbon burnt off but I can't vouch for that, although it does a heck of a job when used concentrated for an annual decarb.

 

[DaleH]

I don't run any additives either & no problems.

Same here ... motors run on fuel, not additives like Sta-Bil or Startron. Now on my tanks using E10 or ethanol fuels, I keep no more in the tank(s) than I'm going to use. But when I ran big V6s motors with a 156-gallon tank, yes.. you bet I added stabilizer to keep the fuel from degrading. Seafoam was my choice, as it also cleans the motor.

FWIW, and I have the original email response somewhere ... but if you want to save 50% on Startron - buy their diesel formula, as is it is TWICE the dose of the gasoline formula, yet for the same price. What they do is dilute the gas formula in half, so run the diesel product and just use 1/2 the stated amount for the same coverage of fuel gallons .... and you'll save 50%. Whether it still is cheaper than Seafoam, I'm not sure. Personally I like the cleaning advantage with Seafoam and have used it with great success for 45-years of boating ... and I ain't much older than that ...

 

[WaltR]

I wish I could find somewhere around here that sells alcohol free gas by more than the gallon tin for an outrageous price. We buy that for Fire Company's gas powered tools. Can't risk stale gas in rescue tools and they have pint sized tanks.

 

[Outlawelectric]

We have several ethonal free stations here in Texas. Most of it is 87 octane, but one in Brownwood has 93. I'm leary of running that 93 as I don't know how much of it they sell or how long it sits.

 

[onthewater102]

It isn't hard to separate out the alcohol from pump gas in areas where alcohol free isn't available - the problem is you don't know to what degree you've lowered the octane rating by removing the alcohol and it's a roll of the dice to see if you can get it stable for your motor. If you start with 93 octane and phase separate out the alcohol you are usually ok running it in small engines - I know my '55 johnson 5.5 seems to prefer the alcohol-free gas.

I don't know if commercially available octane boosters are just concentrated denatured alcohol or if there are some that work without reversing your phase separating efforts, I've never tried any.