Fuel additives for increased compression?

fishjefffish

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I have a 1973 Mercury 650, 3 cylinder. 2 cylinders are a little lower on compression. Ring job coming in the future??? Are there any fuel additives to help in the mean-time?
 

hkeiner

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Re: Fuel additives for increased compression?

I would suggest that you first decarb the motor with some Seafoam to see if the compression improves. Low compression could be caused by carbed-up piston rings. Search the FAQ and elswhere on this furum for information on how to decarb a motor with Seafoam.
 

Rocky_Road

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Re: Fuel additives for increased compression?

I have a 1973 Mercury 650, 3 cylinder. 2 cylinders are a little lower on compression. Ring job coming in the future??? Are there any fuel additives to help in the mean-time?

A 10% difference, across the board, is considered to be within spec.

The real question is...what are your readings?
 

fishjefffish

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Re: Fuel additives for increased compression?

The high cylinder has 150psi nad the other 2 have 125psi. They are the top 2 cylinders. I am going to clean the carb with seafoam then add it to the fuel. Thanks for the advise. Any other ideas? I am new to this. IT IS GREAT!:)
 

hkeiner

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Re: Fuel additives for increased compression?

I am going to clean the carb with seafoam then add it to the fuel.

Perhaps it is just your way of saying it, but decarbing the motor is not the same as cleaning the carbs with SeaFoam. Also, adding a can of SeaFaom to a full tank of gas will not do much to decarb the motor.

To decarb, you can spray Deep Creep (spray version of SeaFoam) into the carbs while the motor is idleing, shut down the motor for a while, then restart the motor and run the motor until the smoke is gone. You can also spray some Deep Creep into the spark plug holes (after removing the spark plugs).

Alternatively, you can hook up a small portable fuel tank and use a strong mix (say 1 can SeaFoam to one gallon of fuel) to run the motor to burn up some carbon. Perhaps this is what you meant.
 

fishjefffish

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Re: Fuel additives for increased compression?

Thank you. I was wrong. I have not heard of Deep Creep/ I got sea foam at wal-mart. Where can I get Deep Creep?
 

hkeiner

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Re: Fuel additives for increased compression?

I have seen Deep Creep at auto parts stores in the past, but not all of them. It will most likely be on the shelf next to the SeaFoam. You might call around before driving to find it.

If you don't find it or prefer to use the SeaFoam you already have, I have seen it suggested to use a spray bottle to spray the SeaFoam liquid. I never tried it myself.
 

fishjefffish

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Re: Fuel additives for increased compression?

I found it on the web and sell it at national parts stores. Thanks for everything.
 

gss036

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Re: Fuel additives for increased compression?

I am assuming this is a 2 stroke engine, so, make sure you had the proper amount of 2 stroke oil to the gas being used.
 

fishjefffish

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Re: Fuel additives for increased compression?

Yes it is a 2 stroke. What do you mean? The proper amount of oil to what? The gas? It is a 50-1 mixture, or to the deep creep I plan to spray in the plug holes?
 

Silvertip

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Re: Fuel additives for increased compression?

Put the SeaFoam in a spray bottle and you have DeepCreep. Spray it into the carbs with the engine idling as directed. Same stuff, just one aerosol and the other is pourable liquid.
 

gss036

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Re: Fuel additives for increased compression?

Yes it is a 2 stroke. What do you mean? The proper amount of oil to what? The gas? It is a 50-1 mixture, or to the deep creep I plan to spray in the plug holes?

As long as you use 50-1 mixture it will work.
 

j_martin

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Re: Fuel additives for increased compression?

The best way to do it is to use a small portable tank, add a gallon of gasoline
and 2.6 oz of 2 cycle oil so you have a 50:1 fuel mix. Add a can of Sea foam.

Hook it up and run it. You'll have to high idle it, and watch which way the wind is blowing, it can be hard on neighbors, and on your love life if it gets to the hanging laundry. (ask me how I know)

It'll probably get to running pretty ragged. Let it kill, or kill it, take the plugs out, and spray a generous helping of deep creep in the holes. Put the plugs back in.

Let it sit at least 4 hours. Overnight is good.

Hook up your normal gas and start it up. Run it a minute or so to clear the Sea-Foam out. You'll probably need new plugs by now, but I've had them come out clean enough to use.

Take it for a ride, then check your compression. It might get up to snuff if the rings were stuck. Don't be surprized if #1 goes down. It might be high because of carbon in the cylinder.

hope it helps
John
 

hkeiner

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Re: Fuel additives for increased compression?

The best way to do it is to use a small portable tank, add a gallon of gasoline
and 2.6 oz of 2 cycle oil so you have a 50:1 fuel mix. Add a can of Sea foam.

Perhaps I am wrong, but if the motor has oil injection on it, then the fuel going through the carbs and into the cylinders will have the correct amount of oil in it and you do not need to add extra oil to the fuel in the portable tank. I didn't think that having a strong dose of SeaFoam in the fuel requires extra oil be added above what oil will be injected into the fuel by the motor's oil injection system. Of course, if the motor is not oil injected, then you must remember to add oil (50:1) to the fuel in the portable tank just like you must always remember to do this to the fuel in the main tank.

If the above is wrong, let us know so that I do not give out bad information to someone decarbing their motor....
 

j_martin

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Re: Fuel additives for increased compression?

I assumed from the age of the motor that it is probably not injected. Also, when giving instructions, it's better to err on the side of safety. If the owner isn't bright enough to figure out his oiling, and has injection. This won't hurt, except maybe wiping out the plugs. On the other hand, if he doesn't have injection and I don't specify oil, SeaFoam alone isn't enough lubrication to keep it alive.
 

hkeiner

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Re: Fuel additives for increased compression?

Your were absolutely right. Having a motor with oil injection myself, I was not considering the age of his motor and that his motor would most likely not have oil injection.
 

fishjefffish

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Re: Fuel additives for increased compression?

Thanks everyone. I have been without power for a week due to ice storm, so that was the reason for my delayed response.

It is not oil injected. I will mix 2 stroke oil (plus a little extra for the sea foam) with the one gallon gas and sea foam and run it to see what happens...when the ice melts here.
 
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