Fuel Additives

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
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Fuel Additives

Postby pcrussell50 » Tue Jun 16, 2020 11:54 am

Fuel additives are a time honored subject, and there are probably as many opinions are there are people.

What additives are you putting in your fuel--if any?

My latest additive cocktail, recommended by my now deceased mechanic (who died in a boat racing accident in Fall 2017), is ordinary Chevron Techron, one bottle per 13-gallon tank, and StarTron enzyme fuel additive used as directed (one fluid ounce per 6 gallons). A cheap borescope looking in the spark plug hole shows a nice clean piston top, however, this was not an exhaustive examination. This was an examination of my most frequently used engine, a carbureted two-stroke-power-cycle engine. I use the same cocktail in my carbureted four-stroke-power-cycle engine that is powering an Alert 17, a Special Service classic Montauk.


Random Notes and thoughts on the matter:

--Having said this, prior to this particular "cocktail", I always added something to the tank. Sometimes SeaFoam, sometimes B12 Chemtool. Just whatever I had lying on the garage shelf, and usually purchased on sale somewhere.

--Apparently one of the primary ingredients of SeaFoam is alcohol, and nowadays pump gasoline has plenty of that as well. I have heard it posited that the alcohol in pump gasoline is generally enough to keep down carbon deposits. Though I don't know how it is with gum and varnish, or how much of a threat those things are.

--A little google research shows that the "magic" ingredient in Techron is PEA (Poly Ether Amine). Gumout brand touts it's use in their products as well

--It used to be that Costco had the best price and availability in town on Techron (by a long shot), but the local Costco that used to carry it is either out, or they are no longer carrying it


So those are my current habits and thoughts on fuel additives. What "cocktails" if any, are others out there using, and in what engine types, from old carbureted two-stroke through fuel-injected four-stroke engines. I always like to gather opinions.


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Re: What additives are you putting in your fuel... If any?

Postby kwik_wurk » Tue Jun 16, 2020 5:16 pm

No fuel additives in my use, except stabilizer in the winter. That said, I only use ethanol-free gasoline; and most on water fuel docks sell ethanol-free gasoline.

I do blow in some "power tune" on a four-stroke-power-cycle 6-HP auxiliary. It is mostly the low-RPM-use that causes build-up.

I have two Yamaha F150 engines, an E-TEC 90, and a Mercury 6-HP. My former engines are too many to list.

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Re: What additives are you putting in your fuel... If any?

Postby Don SSDD » Wed Jun 17, 2020 7:36 am

For 15 years I have used SEAFOAM as a one a year cleaner for carburetors and valves. The alcohol types it contains do not absorb water like ethanol. I use ethanol-free gasoline fuel in my outboard, lawnmower, generator, any gasoline engine that sits around for periods of time. Ethanol gas is fine in my daily-driven vehicles.

I left a generator without a fuel stabilizer once, found brown slime growing in the needle and seat in the carb, from the ethanol fuel I had used.
1986 Outrage 18 with 2001 Honda 130 HP
Former Owner 1991 Guardian 19 with 1994 Evinrude V4 140HP
Former owner 1987 Montauk with 1998 Mercury 90HP
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Re: Fuel Additives

Postby jimh » Wed Jun 17, 2020 7:39 am

I do not routinely use any fuel additives. For gasoline stabilization for long storage, I use the engine maker's product, Evinrude 2+4 FUEL CONDITIONER. I try to buy gasoline with no ethanol.

But I should add this note: the last few years I have not been running the engine more than about 50-hours per season, and that implies I only consume about 200-gallons of fuel. At the start of the season, the boat fuel tank has about 50-gallons of fuel with the 2+4 Fuel Conditioner. So the first 50-gallons the engine consumes will have a fuel additive.

And as the season approaches the end, I resume using 2+4 Fuel Conditioner because I am never quite sure when the last boat use will occur. By using stabilized fuel for the last month or so, I can be certain all the fuel in the system, including fuel in the engine itself, is stabilized. This means that in practice, I am using fuel additives for about one-third the time the boat is running. Only the fuel purchased and consumed in mid-season won't be intentionally blended with an additive.

In Michigan most marina fuel docks are now selling non-ethanol gasoline at 90-Octane, a blend called REC-90. There is state law that requires fuel distributors to have this available. Some highway gasoline stations, particularly ones near boat launch ramps with high traffic, also sell 90-Octane pure gasoline.

If I were to use an additive, I would tend to chose an additive sold by the engine manufacturer. In my case, that is Evinrude. They have the already mentioned 2+4 FUEL CONDITIONER and a product called CARBON GUARD. They used to have another product, FUEL SYSTEM CLEANER, but I don't see that on their website any more.

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Re: Fuel Additives

Postby Phil T » Wed Jun 17, 2020 11:23 am

I used Stabil stabilzer treatment for every gallon.

Non-ethanol fuel is not an option in many areas of the country.
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Re: Fuel Additives

Postby pcrussell50 » Tue Jul 07, 2020 7:08 pm

I use ethanol fuel. No choice. I drain my carbs and tanks at the end of every season, stabilize the fuel I catch, then use it little by little the following season by mixing it in with fresh gas.

I did hear/read somewhere that ethanol in the fuel, notwithstanding the bad things we know about it, is at least pretty good at keeping carbon buildup in check. Anyone have any thoughts on that?

And along these lines I should say that I have several carbureted two-stroke cycle motors that I run on 50:1 pre mix. If any of you are still out there doing the same thing, does that affect what if anything you add to the fuel? Maybe having oil in the fuel contributes to carbon buildup?


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Re: Fuel Additives

Postby Jefecinco » Wed Jul 08, 2020 10:18 am

My left over seasonal fuel goes into the vehicles.