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Charles
Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3341
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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Hello; I am getting ready to winterize my Yamaha stern drive,

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Hello; I am getting ready to winterize my Yamaha stern drive, and am wondering if I absolutely need to drain the block and the minifolds, or can I simply flush and fill the engine with antifreeze for the winter...?
Hello, my name isXXXXX you for allowing me to assist you today.

If you are filling the engine totally full of anti-freeze, yes that is possible. If not them you do need to drain the manifolds and block. Then remove the thermostat housing and pour a gallon of anti-freeze into it after reinserting the plugs. This will ensure that the engine will survive the winter and be good for next spring.

Hopes this helps you out.

Thanks
Charles
Customer: replied 3 years ago.

So, in order to fill the engines systems with antifreeze, I can just place my "earmuffs" around the lower unit intake, and run 5 gallons of antifreeze through the system until the antifreeze comes out the exhaust, correct? and then of course fog the carbeurator, etc. I guess the main question is why would I need to drain the block if I am filling/circulating antifreeze throughout the engine?

Customer: replied 3 years ago.
Relist: Answer came too late.
Brian,
It is much easier and less expensive to drain the block and add the gallon of anti-freeze to the T-stat inlet. This is how is done on most shops. You only need one gallon and not 5.
Customer: replied 3 years ago.

Understood; the issue is that my shop manual states that I need to remove several hoses etc. to drain the system, and it is going to be difficult to do this due to the configuration of my boat's engine compartment. Therefore, I guess I was wondering if running the antifreeze through the system (with the earmuffs around the lower unit intake) would accomplish the same outcome as draining the block and hoses and filling through the t-stat inlet. It may be cheaper with one gallon of antifreeze, but it may be much more difficult in my situation!

Brian,
There are a couple of hoses to remove off the bottom the inlet to the engine and the circ pump. If you have the fitting that attach's to the hose attachment or can pour it in fast enough you can flush and fill the engine that way.
Customer: replied 3 years ago.

but you really didnt answer my question: is there any disadvantage to running antifreeze through the lower unit intake versus draining the engine and pouring antifreeze into the thermostadt intake?

Other than the cost of the anti-freeze, no there is not a disadvantage to doing it that way. If you ran a shop you could have a test tank and back the drive into the tank and run them to fill them up.
Customer: replied 3 years ago.

What do you mean by a "test tank"... a tank full of antifreeze? So basically I will be able to accomplish the same outcome by running antifreeze through the lower unit intake as opposed to draining the block and manually pouring the antifreeze into the thermostadt intake; correct?

Yes a test tank is a large tank full of anti-freeze something like 55 gallons. When you put the anti-freeze into the t-stat opening is only protecting the center head of the engine, since you have drained the block and the exhaust manifolds.
Customer: replied 3 years ago.

So basically I will be able to accomplish the same outcome by running antifreeze through the lower unit intake as opposed to draining the block and manually pouring the antifreeze into the thermostadt intake; correct?

Yes that is correct.
Customer: replied 3 years ago.

thank you!


 

You are welcome
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