Antifreeze in my Inboard Mercruiser... Two questions...?

Question

I have successfully winterized my Mercruiser 5.7L Inboard Ski engine and follwed the service manual for each step - fuel stblz; fogged; water block drain; ect...

I have two questions:

1. Online, I have read alot about filling the open-cooling water system with antifreeze to avoid block cracks. The service manual has no instruction for this step. Has/does anyone do/have experience with this?

2. When I drained the engines lowest water block valves, I notices a bit of rust on the tip of the plug, the first bit of water appeared rusty when drained...should I be concerned? Is this a sign for problems, or is dirty water and a bit of rust normal for an open water cooling Mercruiser engine?



The boat is ouside on trailer, covered, and is a direct drive (engine in the middle of the boat). Currently, winterized with gas stblz, fogged, and block water drained.

Also I live in California's central valley, so the cooldest winter temps will be in the low 20's at worst perhaps 2-5x

Answer 1

Draining the block should be enough for your application,did you drain the 2 exhaust riser(elbow )on the exhaust system.there should be 6 plugs or petcook to open or remove.2 on the block ,2 on the exhaust manifold them self and 2 on the elbows(risers).
I normaly disconect the lower waterpump hose as well.
Is the transmision water cooled.look st that as well

Answer 2

I never had much trouble with freezing when I lived in CA, but I lived in the southern part of the state. Now that I live in the Midwest, I pay more attention to my vehicles cooling systems. A good rule of thumb is to always remember that any temperature cold enough to freeze water will cause the water to expand, cracking the block. Just because the service manual doesn't mention this, don't take any chances. Add anti-freeze to any water that is subject to freezing. As far as the rust, it's probably from sitting for even a short period of time. Even a few days is enough time for rust to start forming. Although I've never had a pleasure boat, when I use to race, I would always drain and flush the engine after each weekend of racing. You may or may not want to take the time to do this with a pleasure boat, but one thing about rust, once it starts, it can be hard to stop.

Answer 3

don't worry about the rust or some black water that comes out. this anti-freeze thing has baffled me for years...i've been in the business for 22 yrs. i suspect that's like putting nitrogen in your tires. if you have a "closed" system, it should be full of anti-freeze anyway. if "open", if you drain the block (5 points), you'll be good. make sure your xmission doesn't have any water in it.

Answer 4

Rusty- no worry.
Did you circulate anti freeze threw the cooling system ?

If not there are low spots where fresh water is traped. --Will freeze & break

Answer 5

1.should fill just like your car 2. it is normal but you still need to flush it on regular basis