Mercruiser 5.7 MPI Horizon Winterization

dtwilson110 · October 2017

Well it's getting to be about time to winterize the new boat. This is my first closed cooling system boat. I plan on testing the antifreeze in the engine to make sure it will hold up to the winter temperature. I have heard that there is an air system on the motor that I can use to drain the engine of water. Then can I just run antifreeze through the outdrive to winterize the motor? Any advice would be appreciated!

Dream_Inn · October 2017

You are correct. My advice, run the engine with fresh water first thru muffs. Shut off, pump the air system and make sure water is coming out. I also pull the blue plug on the hose from the seawater pump to the drive (water can sit in there even after using the pump). Then I switch over to the pink and run it thru. After using the hand pump, there is a valve that opens, then should close on the bottom of the seawater pump. I've seen it not always close on some boats. This is usually due to not exercising it.

dtwilson110 · October 2017

Ok thanks! How exactly do I pump the system?

reneechris14 · October 2017

Did mine yesterday.I drained the right side of the motor with the blue wing on the water separator. pull the hose of the sea strainer stuck it in 5 gal bucket of pink stuff started the motor until it came out the out drive and shut it down. If you close the seacocks you go though the muffs on outdrive. Just remember open when done, don't want to leave water on top of the ball value.

Liberty44140 · October 2017

Yea I've got 350 horizons with the air actuated pump. First, use hand pump and pump her up until green dots are erect. Then water will be pouring out of the bottom of the water pump and plastic water housing. When that is done remove air pump and pull release valve so green dots go down. Then I still pull all 4 blue drain plugs and do a quick on/off at the ignition to get water out of the pump and engine. Replace plugs. I have thru hulls so I close them and I don't touch the strainers. Hook a 5 gal lowes bucket with a spigot to the drive via the muffs and run pink stuff through. I've been told 2 gal in enough. Last year I did 3 gal per engine and this year I am doing 4 gal per engine to be safe. You start to see pink exhaust after a gallon or so. After bucket is empty shut off engine and re open thru hull valve. Done. I wont fog, tried it last year via a 3 gal remote tank with the cocktail and it was more hassle than it's worth. Everyone here says no need to fog.
Anyone feel free to punch holes in my process...

dtwilson110 · October 2017

Image: https://us.v-cdn.net/5020499/uploads/editor/0e/ctb4rf5cyewf.jpg

dtwilson110 · October 2017

It looks like I am missing the pumps. Does anyone know where I can get a replacement pump? Is it the same as a bicycle tire pump?

Dream_Inn · October 2017

Yes, you should be able to use a bicycle pump. Just remember when done to pull the little valve to release pressure (has a ring on it).

Liberty44140 · October 2017

Yep, I use the hand pump that I use for my mountain bike. Came from amazon

reneechris14 · October 2017

I'm always nervous about draining the pump and losing the prime, so that why I just drain the right side, when the pink goes in does not get diluted. I use 4 gal per motor gives me a good sold pink flow of the

Liberty44140 · October 2017

I hear ya. Was worried too but it worked fine. There is a u tube video out there of a guy fully draining 350s on a 2002 342 RWC and then ran 3 gal per side through on muffs from a bucket. Gave me confidence

Dream_Inn · October 2017

I drain mine all the time and it's fine. Heck, it drains when I raise up on my lift every weekend (& I know it does because when you do have a seawater pump issue - wearing the inside- it shows up immediately when you try to start after lowering in water).