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winterization for mercruiser 350 mpi mag

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Gang, just finished draining my new to me 2003 Chap 243 with 350 mag mpi mag... 1st I/O thus the 1st time I've had to winterize so I'm a little nervous. My manual shows several different options that the motor could have as far a locations of drain plugs....I pulled the one on the front of the motor at the bottom, then pulled the one on top of the front of the motor on the thermastat housing and then pulled the two blue plugs located on the starboard side of the motor located towards the bottom of the motor....So total of 4 blue plugs that I pulled. Is that all of them??? Model # of the motor is MCM 350 MAG MPI... Also, none of the dealers here put anti-freeze back in the motor, they all say that it is over kill, your thoughts? I changed the oil and filter, emptied fresh water tank, fogged the motor. The fluid in the remote tank for the lower unit fluid is not milky...does that mean I do not need to pull the screws out of the lower unit and check for water in the lower unit?? Sorry to ask so many questions....just do not want to learn this the hard way!!! Any help would be appreciated.

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The tank up top for the drive does not necessarily indicate that your drive fluid is water free. Most of us here change the out-drive fluid just like we change the engine oil. I put antifreeze into the engine as it has corrosion inhibitors that help reduce rust within your engine.

Your manual should be specific on where your drain plugs are but typically their are four. One for each side of the block down toward the bottom of the engine and one on each exhaust manifold underneath them. I also remove the large hoses to the water re-circulation pump as water can remain in those areas.

I add antifreeze by removing the thermostat housing and pouring it directly into that hole filling it until it won't take any more. Then I put a new gasket on the housing and reattach.

I have a Volvo and not it is a little different but the engine basics are still the same.

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Sounds from your description that you might have a Bravo drive vs. an Alpha. I take a hose to help pour non-toxic antifreeze down the thermostat housing and exhaust manifolds, and run some non-toxic through the seawater pump on Bravo models.

If you have a Bravo, you should see a quick connect fitting in the hardwall pink hose about 1' behind the seawater pump itself. Pull the pin, and then pull the hose connections apart from each other. I shove a smaller hose inside the 1' hose section off the seawater pump, fill with non-toxic, and then, with the kill switch flipped down on the remote control, crank the engine over for a few seconds. Keep filling the hose, and cranking until you're confident non-toxic has been pump through your seawater pump. Lastly, put everything back together.

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