Winterizing Mercruiser

[billallison]

I'll be doing my own winterizing this year and have tried to educate myself on the best way to deal with the cooling system. I have a Mercruiser with a single point drain and have decided to add antifreeze for insurance against freezing if water is still in the system. However, I've read opinions on whether to use it or not use it, and how to put it in - using muffs, disconnect the hoses and pour it in, or pour it down the thermostat housing.

I'm not interested in removing the thermostat housing and replacing the gasket, so I'd like to know the procedure on pouring it in the hoses. Do I drain the water from the engine, then disconnect the 3 large hoses connected to the thermostat housing and pour in the antifreeze until full?

 

[Raystownboater]

Re: Winterizing Mercruiser

One way that has worked for me is to make your own winterizing kit. I got a 5 gallon gas can, fitted the nozzle with a short hose and connected the other end to your muffs. Idle the engine until the antifreeze discharges and your system is winterized. You can follow that up with spraying fogging oil in each spark plug hole

 

[Bondo]

Re: Winterizing Mercruiser

I have a Mercruiser with a single point drain

Ayuh,... I'm not to thrilled with those systems,...
There's no way to know which drain ports have drained, or if several are plugged up with crud...

I'd pull the whole thing off, 'n plug the drain ports with plain ole brass pipe plugs...
That way, ya can get a screw or nail into the hole to prod the crud out...

Btw,... A Completely drained motor don't need antifreeze, as Air, just Don't freeze...

 

[John_S]

Re: Winterizing Mercruiser

If you are going to use anti-freeze, drain it completely, and then fill engine via the water inlet supply line. Feed it direct and will not have any questionable mixing of water to dilute and reduce the anti-freeze effectiveness. I use an anti-freeze that is specific to I/O winterization than has an anti-rust package. My boat sits almost as long as the amount of months I get to use it.

 

[paultjohnson]

Re: Winterizing Mercruiser

One way that has worked for me is to make your own winterizing kit. I got a 5 gallon gas can, fitted the nozzle with a short hose and connected the other end to your muffs. Idle the engine until the antifreeze discharges and your system is winterized. You can follow that up with spraying fogging oil in each spark plug hole

That method scares me ... How do you know the thermostat has opened, allowing water thru the block. How do you know the stat isnt closed and causing the coolant to by pass the engine ?

 

[billallison]

Re: Winterizing Mercruiser

If you are going to use anti-freeze, drain it completely, and then fill engine via the water inlet supply line. Feed it direct and will not have any questionable mixing of water to dilute and reduce the anti-freeze effectiveness.

Thanks for the reply. However, not sure which line is my water inlet supply line. Do you mean use muffs and introduce the antifreeze with the engine running? Or are you referring to a line on the engine? See attached photo of my engine.

 

[paultjohnson]

Re: Winterizing Mercruiser

Thanks for the reply. However, not sure which line is my water inlet supply line. Do you mean use muffs and introduce the antifreeze with the engine running? Or are you referring to a line on the engine? See attached photo of my engine.

The water supply hose is hooked up to a fitting that goes thru the transom, where it receives water from the outdrive. On my mercruiser it comes out of the transom, then thru the PS cooler, then up to the engine.

 

[Bondo]

Re: Winterizing Mercruiser

Ayuh,... The water feed line from the drive is the 1 at top, portside of the t-stat housing,..
It comes up over the manifold, from the drive...

With all that room to work, I'd definitely strip off the single point drain system...

 

[billallison]

Re: Winterizing Mercruiser

Ayuh,... The water feed line from the drive is the 1 at top, portside of the t-stat housing,..
It comes up over the manifold, from the drive...

Thanks for the response. Just to be clear, I've attached another photo. Is this the line you are referring to?

If so, I'll drain the system, then remove the clamp from that line, fill it with antifreeze, and re-connect it.
In your opinion, I don't need to do the same to the starboard side hose?
Thanks for your patience.

 

[Bondo]

Re: Winterizing Mercruiser

View attachment 114243View attachment 114243

Thanks for the response. Just to be clear, I've attached another photo. Is this the line you are referring to?

If so, I'll drain the system, then remove the clamp from that line, fill it with antifreeze, and re-connect it.
In your opinion, I don't need to do the same to the starboard side hose?
Thanks for your patience.

Ayuh,... If ya fill that hose with anything, it's gonna just run out the Drive...

The Big hose on the starboard-side, should have it's Lower end pulled from the circulating water pump, to get the qt. or so outa the pump...

 

[John_S]

Re: Winterizing Mercruiser

After you have completly drained it, including the lower hose, attach a short hose to that fitting. Close the petcocks and attach the lower hose. Slowly fill the engine with anti-freeze via the short hose. Keep track of how much anti freeze you use, and keep in mind that you can't raise the level past the top of you exhaust elbow, as it will run down the exhaust pipe and out drive. I drain it into the bilge, and back into containers in the spring.

As Bondo has said many times "air does not freeze". It is simplier to perform and less likely to mess up and cause issues.

 

[billallison]

Re: Winterizing Mercruiser

Thanks for the replies. I will be performing all of the winterizing on the boat next weekend.
I know that air doesn't freeze, but I'm not familiar with the internal cooling system of the engine and want to ensure that there is no water in it after it's drained. I will drain it, then pull off the big hose and the top hose connected to the thermostat and pour in some RV antifreeze.
Thanks again for your help.