I have searched the sea foam topics already on here but none really fit the question I have so here goes. I have a 1997 Yamaha 115 two stroke no oil tank you mix the oil in the gas tank. Now my problem is that the motor starts stuttering/skipping above about 3800 rpm the more you run it the better it gets but does not completly go away. I had thoughts of running some sea foam in the gas tank at a mixture of 1 ounce per gallon of gas to try and help clear it up. I have changed the plugs,water separator and cleaned the bowl on the side of the engine. It did do some sitting before I bought it. You here good and bad about sea foam so mabye a mechanic on here could clear this up, or offer suggestions on what I could mabye do to solve this problem. I am not a boat mechanic but have worked on alot of things I just dont want to ruin such a expensive item. Also is there anything I should run in the gas all the time, all I have ever had was oil injected motors Thanks in advance.
Key West 1720 Sportsman
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Doubt very seriously running the Seafoam will hurt anything. It may not help anything either. My guess is dirty carb(s).
Need to decarb. Spray directly in the carbs, and also on top of the pistons. Lots of discussion on the web and and on here how to do this.
Will probably take 2 cans. Seafoam spray decarb will work or their is also another brand called valvetech I believe.
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Wilderness Ride 115
spraying de-carb directly into the throat of the carbs will do nothing to help clean the carb.
it will remove carbon build up from the pistons and combustion chamber.
mixing 1 oz per gallon in your fuel tank also isn’t really going to do much either.
if you have a dirty carb, and you keep running it, you WILL BLOW YOUR MOTOR.
the only lubrication you get on a 2 stroke comes from the fuel and oil mixing together and washing over all the moving parts before it gets into the combustion chamber.
a dirty carb means no lubrication
use dunks method to decarb with seafoam, and it will decarb and assist in cleaning the inside of your carbs
if it still doesn’t run perfect, take it to a someone like us or any shop you trust and have them check it out.
you don’t want a $400-500 repair to cause you to replace an engine
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Also, in a motor that old I’d be running only non-ethanol fuel. Ethanol treatment will help, but my mechanic says “stay away from ethanol fuel”. He says he gets a lot of repair work thanks to ethanol.
That motor should have a manual choke, When the motor starts messing up bump the choke, if the motor picks up and runs better for a second or two then the carbs need to be cleaned. The issue may be electrical if the carbs are not dirty, very rare for electrical issues on a yamaha but it happens.