"Seafoam is like alot of other
"Seafoam is like alot of other "cleaners" or "conditioners".
Seafoam should help remove carbon, gum, varnish etc.
Certainly can't hurt as a "preventative" and would be similar to running fuel conditioner in your vehicle.
Some guys swear by it, others don't bother.
I'm somewhere in the middle - can't hurt, but there really is no "magic in a can" - I tend to believe alot of the results are exagerated, not on purpose, but just because someone "thinks" they notice a great improvement.
I decarb my motors once a year with Mercury PowerTune and then simply run gas stabilizer (as is recommended by all the mfgs if you use gas containing ethanol), and have never had a gummed carb, fouled plug, stuck reed etc - and that is on my 3 outboards, the newest a 1991 model, with a total operating time well in excess of 5000 hours amoungst the 3 motors.
If you do your annual maintenance and do not abuse your motors, Seafoam may very well help, but it's not "mechanic in a can" and can not be a substitute for proper care..."