Forgive me I'm sure you see seafoam questions everyday but I'm new to this so bear with me. I have a 3hp gamefisher that I got used and the original tank had a huge crack in it (found out the hard way) So I ordered a new one and replaced it and when I tested the engine out it will only run strong with the choke a little open. If I put it in the run position it sputters a little. I've heard seafoam works wonders so I bought a can at napa today. Reading the Tanaka owners manual I found online it says it is a 1.3L tank which converts to .34 gallons. Is it ok to run .5 oz of seafoam to one full tank? Also I have the motor setup in the back yard do I need to run a full tank with it non stop so the seafoam can work? It is an air cooled motor so I should be able to run it as long as I need to. Thanks any help is appreciated. Should I also replace the spark plug? I don't know how old the motor is but it's definately not even close to new.

Well, yes to the question on the .5 oz of seafoam to one full tank -
BUT, sounds like you might have a dirty carb- Don't exspect Seafoam to fix that unless you pull the carb & clean it with it -

Rebuild the carb and throw some plugs in it.