4 Stroke Maintenance

I bought a new (to me) boat with a 115 4 stroke Merc(Yamaha)on it and would like to know how to keep it running at it’s optimum. I’ve only had 2 strokes in the past and never had to add any fuel / oil additives to them. Do I need to add Seafoam every other tank of gas or anything????
Is winterizing the motor different? Should plugs foul out?
Is octane a contributor? Should I add a warm-up /cool-down period daily?
Any help would be appreciated.

I’ve got a 2002 115 Mercury 4-stroke, bought it new. I was running sta-bil and this year I switched to seafoam. I spray the cylinders every year for winterization. I change the plugs every other year. It runs great not one problem! I also replaced the water impeller this past winter, although it was not necessary, the old one looked great. Be careful if you troll with it tho, they do ‘manufacture’ oil. gas will get in the oil so you should change it often then.

I’m on my fifth season with a Suzuki and the only additive I have used is Seafoam late in the fall for storage. I do hose all cylinders down with fogging oil for the winter. I run 87 octane all the time. Still has the original plugs after 500hours on motor (most of that is trolling, so idling). I give the motor a five minute warm-up before WOT. I change the oil every 100 hours, and then its turn the key and go.

I’ve got a 4-stroke Yammy 90 and have nothing but great things to say. For maintenance, I change oil every year, lower unit also, and I change plugs each year also, and keep the old ones in the boat as a backup. Yammy suggests running their gas additive and I do it at 1 oz per 10 gallons. I run Stabil also, especially at year end.

Then, turn the key and enjoy the quiet humm.

Dave

Thanks all for the info. That is exactly what I wanted to find out. How is this motor going to run when it’s 30 degrees outside? I’m assuming that other than an extended warm-up, it should be just fine.

As for running in 30 degree weather my merc 40 4-st runs just great in the cold weather, we only change the oil and lower unit grease once a year and run some seafoam through it at the end of the year and at start of the year.Starts right up in the spring just like i ran it the day before.

P.S you are going to love the MPG of the 4-st.