I have a 1998 175hp Johnson with carbs on it. I've always used Seafoam in the past. I just picked it up from the shop for a pre-season tune-up and the shop told me to use Mercury Quickleen in it. So I will be changing from Seafoam to Quickleen. It will be interesting to see if it makes any difference as the year goes on....

I use 1/2 a can of Seafoam once a month...........or about every 3rd time I get gas. I never fill it. I fish 3-5 days a week on a small lake, and even if my trips are 2-3 hours, or 12 hours, gas usage is about the same. I have a small 4-stroke, and use about 5 gallons of gas every 10 days. I add Startron with the Seafoam during "wet weather" periods. Like if I have been out in the rain a lot, or in the spring/fall when the nights are cool and damp. The first time I get gas in the spring I usually add both, and starting in mid-late October, I add both every time I get gas to make sure, just in case that trip is my last for the year, any gas left is treated for the winter.