There is some better stuff that mercury makes. It is called Power Tune. It's a spray that you shoot directly into the carb(s) and it is designed to clear out carbon deposits and gunk and just make the motor run smoother. Available at any Merc dealer.
I talked to a guy at Mercury customer support the other day and he recommended Quickleen fuel additive. When I asked him how it compares to Sea Foam, he said it blows it away. I just ran a tank of it through my boat today and I have to admit I don't see a difference.
My dad has used it in his boat and it works great. I just picked up his 1991 Ranger with a 1993 Mercury XR6 150HP on it. It had full
tanks which he had put sea foam in. The boat had been set up for 2years. I took it out last Tuesday and it ran like a top (it did take
a while to get the motor primed). I was thinking of using Stay-Bil but after this I will probably use sea foam.
