The owners manual and almost every Yamaha Outboard mech I talk to stronglt recommends using Yamaha Ring Free every time boat is refueled.

Anyone know who makes it for Yamaha and what it really is?

The mechanics to a man sao they not only use in outboards but also use it in cars, motorcylces--any motor and get lots of benefits.

Since Yamaha stresses it in owner manual and it gets so much support I'm following instructions but sure would like to know more about it.

At my store we recommend using it it in all 4-stroke outboards.
It reduces the carbon build up on the ring and valves. Some customers who troll for long periods of time will start to get fuel in the oil and poor performance, after a few tanks with Ring Free the problem goes away. We have tested it on old pistons in a pan full of Ring Free and after a few hours the carbon comes right off. Mercury Power Tune works good to.
Most of the failures we see are carbon related, Rings stick and piston gets hot.
I have put it in my boat with Mercruisers but can't see any performance gains. If you call the Yamaha tech line the first thing they ask you is, is the customer using Ring Free?

Valve tech marine decarbonizer works nicley too..

WAG, perhaps some form or type or Marvel Mystery Oil? Good stuff for Chevy engines, no clue on OB. This looks like a call to Hydrocrusier is in order. I am guessing that they are not going to tell us what it is if you can get the same stuff for less elsewhere.