4-Stroke Winterize Tips

I’m thinking of winterizing my boat this winter for the first time on my own. I have a 115 HP Mercury 4-Stroke. Other than changing out the lower unit oil, putting some fuel stabilizer, charging the batteries, and disconnecting them what else am I missing?

For 9 years here’s what I did with my Merc 4-stroke.
Stabilize gas. Run engine out of gas. Lower unit, oil change and fog thru air intake not pulling plugs.

X2

I have a Yamaha F90 and I only change the lower unit oil, the engine oil and add the recommended amount of Stabil for storage (run the lesser amount of Stabil and Seafoam during the year). Depending on the winter, my boat sits in the garage for 3 to 4 months, the rest of the time I use it on weekends.

This winter, who knows, I may be using it all but 2 months the way the weather looks in southern WI

I’ve always been told use either seafoam or stabile, never mix, they don’t play well together ironically.

Dusty Gesinger wrote:

I’ve always been told use either seafoam or stabile, never mix, they don’t play well together ironically.

I’ve always read/heard that there is no issue using both, Seafoam acts as a cleaner and fuel stabilizer while Stabil is a fuel stabilizer. Havent had any engine troubles in 5yrs

It probably depends on who you talk to and what you read

I’ve heard that running a 4-stroke dry and storing it over winter can leave the seals cracked/dry – is that not the case?

Nate Northup wrote:

I’ve heard that running a 4-stroke dry and storing it over winter can leave the seals cracked/dry – is that not the case?

A little bit incomplete info. Anything bigger than a kicker motor is most likely fuel injected. There is nothing to run dry. With a carbureted motor, even when I’ve theoretically run it dry, I’ve had ethanol fuel problems in the Spring. I take the plug out of the bottom of the carb and try to get every drop out. So, I drain my 8 HP but do nothing to my 150.

I have a question – why are outboards and boats so hard to understand? If you line 10 people up and ask them what steps to take to winterize a motor you will get 10 different answers. And these answers don’t differ slightly based off of preference, they are drastic. Ive had “professionals” tell me exact opposite things like “seafoam is all you should put in your motor” and the next guy says “seafoam will DESTROY your motor”! How is a guy that isn’t a mechanic supposed to learn from that situation? I just don’t get it! I mean this kind of thing doesn’t happen with other mechanic products. Take a car for example, you take a broken car to 10 different mechanics and you might get a few that have a different opinion but by and large most of them will diagnose something the same and certainly if the problem is determined to be a bad fuel pump they don’t have 10 different ways to fix it there is 1 way and that’s it! Why is there so much disagreement about boat maintenance and motors? Its baffling and frustrating to me. Sorry for the rant, I didn’t mean to hi jack the thread

crappie55369 wrote:

I have a question – why are outboards and boats so hard to understand? If you line 10 people up and ask them what steps to take to winterize a motor you will get 10 different answers. And these answers don’t differ slightly based off of preference, they are drastic. Ive had “professionals” tell me exact opposite things like “seafoam is all you should put in your motor” and the next guy says “seafoam will DESTROY your motor”! How is a guy that isn’t a mechanic supposed to learn from that situation? I just don’t get it! I mean this kind of thing doesn’t happen with other mechanic products. Take a car for example, you take a broken car to 10 different mechanics and you might get a few that have a different opinion but by and large most of them will diagnose something the same and certainly if the problem is determined to be a bad fuel pump they don’t have 10 different ways to fix it there is 1 way and that’s it! Why is there so much disagreement about boat maintenance and motors? Its baffling and frustrating to me. Sorry for the rant, I didn’t mean to hi jack the thread

This is why boats are referred to as “she”. Impossible to figure out and very temperamental.

^ and expensive.

Dave, you’re awesome man! Thanks for the explanation – so, I did the right thing last winter when I stored my Jiffy 4G “dry”? Haha I’m just going to always bug you when I have questions about stuff.

And crappie, I hear ya – but, folks on here are usually pretty great about answering questions. Ask and you shall receive, brotha!

crappie55369 wrote:

I have a question – why are outboards and boats so hard to understand? If you line 10 people up and ask them what steps to take to winterize a motor you will get 10 different answers.

crappie, let me break it down simple, outboards don’t really need to be “Winterized”, inboards do (freeze plugs removed). What has been described here by different individuals is really end of the year maintenance. That’s why there are such a variety of answers and someone isn’t doing it right while others are doing it all wrong. For the guys that live in the frozen tundra, they just try to get rid of fluids that might contain moisture and freeze. In Cali, I do nothing to my motors until Spring.

Thanks everyone for the responses.