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Winterizing the Mercruiser 3.0

I do this once a year, and don't remember all of the details. So I thought if I documented it here, I could refer back to it next year and make things a litte more streamlined. Plus it will help make sure I don't miss anything. This year I realized after I started filling the exhaust manifold with antifreeze that I had forgotten to drain the manifold. When I looked at the photos, sure enough, there is the drain plug in the bottom of the exhaust manifold.

Here's why this might be important. It takes me several hours to winterize the boat. If I can cut that down to an hour, then I can reserve it to a time later in the season. But if it's going to take three or four or five hours, then have to start early enough

I was at the lake today (no boat because mine is in the process of being winterized) and wow it was a really nice day, and I thought, it would be nice to have the boat out on the lake today, but alas, it's already being winterized. The second thought was, if I had a sailboat, it requires minimal winterization. Pull it out of the water and maybe do some cleaning. So with a sailboat I could be sailing much later in the season. In fact, I could sail all season long. If there's a warm day in January, I could get in the water for the day.

It may also help someone else who's doing it for the first time (or even the second or third time).

You will need:
- About 1 1/2 gallons of RV/Marine antifreeze. Walmart is a good source.
- A thermostat housing gasket
- Some gasket sealant. I used blue Permatex RTV sealant last year. It is a little hard to get off, so maybe I'll try rubber cement this year.
- 1/2 inch socket for the thermostat cap
- 5/16 socket driver or maybe a screw driver depening on your hose clamps
- 7/16 socket for the manifold drain. My block drain has a wing nut plug. I can get it out by hand.
- 7/8 deep well socket and drive extensions for the spark plugs.

Remove the drain plug in the transom and put a bucket under it if your inside.
Remove block and manifold drain plugs. 7/16 socket for the manifold drain plug.

Use a 1/2 inch socket to remove the cap screws for the thermostat housing and then pop the thermostat housing off. The gasket separated with the housing and block. I had to scrape the RTV sealant and gasket material from both the block and thermostat housing. This year, I'm trying rubber cement as the sealant. Maybe it will be easier to clean the gasket off next year.
Remove the coolant hose from the manifold, and then repace the drain plugs.
I use a long neck funnel to pour the antifreeze into thermostat well in the head, and into the water port on the top of the exhaust manifold (where the hose came off). Fill them until they are full. I really wonder if you couldn't get away with just draining the block. If it drains completely or nearly, then you really shouldn't need antifreeze. I guess the antifreeze is cheap insurance at $2.87 per gallon (Walmart), just to make sure.

Once you have everything drained and filled, jack the front of the boat up so that the bilge drains as best as it can. You will still need to use a rag to dry it out. I don't get in the boat while I have it jacked up like this.
Pull each spark plug, squirt some oil in each cylinder and crank the engine over. You might put some rags or paper towel in front of the spark plug holes because the cylinders will blow some of the oil out. DO NOT crank the engine with the plug back in. You will wreck the engine if you do that. The oil will not compress and you will hydraulic lock the pistons and bend a rod, or break a cylinder. By next season, the oil will have run out of the cylinders and you'll be fine to start it.

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