Fuel additive?

[Duncan]

Should I add a fuel additive with every tank?

My normal marina sells 89 octane but I occasionally have to use 87. Would an octane booster be beneficial on those occasions?

What about regular use of a cleaner such as Seafoam?

A marine additive for ethanol-containing fuel?

Just curious what others are using periodically and/or regularly.

[chpthril]

The preferred Octane level would be 87, so no, you do need to add an octane booster.

I do not think that an additive, even one for ethanol fuels, is needed with every tank, once in awhile should be fine. The ethanol itself will not harm anything in your fuel system, but ethanol can increase the moisture level in the tank and also lead to phase-separation. An ethanol targeting additive will help the water pass and prevent the phase-separation. If anything, the fuel/water sep may need to be changed at an earlier interval.

[dogbert]

I could see using Stabil as a regular additive if you're going to be using your boat occasionally or storing it for long periods of time.

[ajholt7]

87 octane and stabil marine with every tank is what I do. Probably don't need to add the stabil but, it is so hard to find a station without ethanol. There is no reason I can think of to run higher octane than 87 since that is what these engines where designed to run on.

[Ewok]

I use the marine stabil in every tank as well. My schedule changes like the wind so I can't plan to be out on the boat every weekend.

[TeamAllen]

87 octane with Marine Sta-bil as well.

[boatwakes]

Please see my post under "fuel water separator change" regarding ethanol. Ethanol WILL cause damage to your fuel system and engine if not addressed properly. Do not use additives containing ethanol, it only adds to the problem. We've seen less corrosion issues with regular Sta-Bil than marine Sta-bil in engines we've had to tear down because of fuel system problems. I just got finished installing a new 7.4 Merc Horizon in a 38' Sea Ray that lost the top of its #6 piston because of ethanol. Again, it will cause problems if not addressed properly. We reccomend any stabilizer that doesn't contain ethanol, namely a product called PRI-G carried at West Marine and only use 87 octane, the computers have to do funny things with the higher octane fuels.

[chpthril]

Please see my post under "fuel water separator change" regarding ethanol. Ethanol WILL cause damage to your fuel system and engine if not addressed properly. Do not use additives containing ethanol, it only adds to the problem. We've seen less corrosion issues with regular Sta-Bil than marine Sta-bil in engines we've had to tear down because of fuel system problems. I just got finished installing a new 7.4 Merc Horizon in a 38' Sea Ray that lost the top of its #6 piston because of ethanol. Again, it will cause problems if not addressed properly. We reccomend any stabilizer that doesn't contain ethanol, namely a product called PRI-G carried at West Marine and only use 87 octane, the computers have to do funny things with the higher octane fuels.

Can you explain how the ethanol will damage the internal metal parts of the engine?

Thanks.

[dogbert]

Ethanol ate through the diaphragm on my fuel pressure regulator. Any rubber part (o-ring, seal, gasket or diaphragm) will have a shorter life if there's ethanol in the gas.

[chpthril]

Ethanol ate through the diaphragm on my fuel pressure regulator. Any rubber part (o-ring, seal, gasket or diaphragm) will have a shorter life if there's ethanol in the gas.

On older engines, yes, but ethanol is not new and engine manufacturers have been using ethanol resistant rubber and plastic in the fuel systems for quite a few years now.

[dogbert]

I'm just saying...

[TeamAllen]

It also seems the ethanol percentage keeps increasing? IDK?

[boatwakes]

Ethanol will absorb water, moisture in the air, condensation in the tank, etc. So to be technically correct, the water/moisture and not the ethanol is doing the damage to the combustion chambers, cylinder walls, piston rings, exhaust valve seats and valve faces. With previous MTBE's in gasoline, water NEVER was abosrbed into the fuel but phase separated and was spun out in the water separating fuel filters. Phase separation is a good thing when dealing with fuel, diesel or gas because it allows the fuel to remain floating on top of the filters and able to flow through the fuel system and be burned as normal. Since ethanol was introduced, I have had more efi fuel pumps fail, pressure regulators fail, recently had a customer with both problems have his injectors lean out to compensate after detonation began to occur causing a 1" radius of his #6 piston crown to evacuate the cylinder chamber. Ethanol eats fiberglass, so a few of my customers with fiberglass tanks have now had to spend thousands of dollars to remove glass tanks and replace with aluminum.
Because ethanol absorbs water, it lowers the octane rating of the fuel it's emusified within (Phase inclusive). Lets say you fill your fuel tank between uses like we all used to do. The boat sits for a few weeks and the relative humidity of summer begins to take its toll on the fuel in the tank by absorbing into the gasoline. Your octane rating drops to 86, 85 or even lower. It takes more fuel to make the same power and now detonation is starting to happen because the computer can't retard timing more than 6* and snap! A piston ring, a piston crown, valve face, valve seat and the list goes on. Ethanol is bad for fuel systems but was touted as being good for the environment, so it's here and we've got to deal with it.
There are also several good write ups and articles dealing with this subject throughout the interwebs I'm going off first hand experiences and not hearsay: I owned a marina fuel dock in Newport Beach, CA for 9 years and have been working on marine engines and their related systems for the past 12.

[TeamAllen]

Here is another article about Ethanol in fuel I found, in my off road magazine.

http://www.offroadadventures.com/articles/view/id/474

[AdaminMN]

Gotta love Sta-Bil!