4.3L MPI Winterizing

[05StingRay]

OK so I have read what seems to be a thousand different threads and watched videos on winterizing these motors but they all seem to be a bit different. Whether it be the carb vs MPI or raw water for closed system, I just can't seem to find enough to make me feel comfortable. I live in Iowa so we have some definite cold weather here. My Mercruiser manual says I just need to open the single point drain as well as the blue plug on the thermostat housing and I should be good to go, but I definitely want to double check that I am not mistaken! I also had an issue with a broken blue plug that required me removing the thermostat housing at the same time and replacing the thermostat while I am there.

Ok so after all of that explanation, am I good with just draining the way the manual stated? Would it hurt anything if I were to dump antifreeze in the hoses from the thermostat housing and in to the where the thermostat should sit? Just looking for some help so I don't get myself in trouble come spring. Thanks

Nate

 

[Bt Doctur]

The biggest issue with that system is that the block drains get clogged and dont drain the block. Remove the hoses at the block to verify they are not clogged with sediment

 

[Starcraft5834]

The biggest issue with that system is that the block drains get clogged and dont drain the block. Remove the hoses at the block to verify they are not clogged with sediment

yup, yup and yup.. air dont freeze, just drain it........

 

[HT32BSX115]

OK so I have read what seems to be a thousand different threads and watched videos on winterizing these motors but they all seem to be a bit different.
Ok so after all of that explanation, am I good with just draining the way the manual stated? Would it hurt anything if I were to dump antifreeze in the hoses from the thermostat housing and in to the where the thermostat should sit? Just looking for some help so I don't get myself in trouble come spring. Thanks

Nate

Howdy Nate, Like the others said, NO. You are not "good" draining the way the manual states using the single point drain.

That was OK when the engine was 'new" and there was NO loose rust in the block and manifolds. But the cast iron block and manifolds begin rusting immediately and begin to slough off rust flakes. Those flakes and other debris that might be in the cooling system WILL block one or more of the hoses and/or block drain points and prevent water from being drained fully.

And don't think you're ok by only "Single point Draining" and THEN filling with Anti-freeze, because you could have clear water in areas inside where the concentration is not adequate (because the AF doesn't mix completely) to prevent freezing.

Be sure to drain the block and manifolds on both sides AT THE BLOCK DRAIN POINTS (I.E. remove the hoses and fittings in the block. Poke a small screwdriver in those holes to free up any rust/debris that has "dammed" up the hole(s)

After you drain everything, you can then fill with AF if you wish, but it won't be necessary

Cheers,

Rick

 

[Scott Danforth]

the single point drain was developed to get higher consumer reports service points to help sell new motors. worst thing for motors for the reasons described above.

 

[Rick Stephens]

I would think that permanently removing the hoses and fittings to the block drains and going back to simple block drain plugs would be safer and easier in the long run than all the hassles it takes to disassemble the single point system each year.

 

[H20Rat]

Once you have done it a couple times, pulling the plugs and shoving a screwdriver up the hole to clear it is a fairly quick process. I can winterize in maybe 10-15 minutes, most of that is just finding the toolbox.

 

[Bt Doctur]

I am removing that system on all my customers boats to install brass plugs or the blue plugs. I remove the manifold fitting with the check ball and replace it with a brass elbow with the blue plug drain

 

[HT32BSX115]

I would think that permanently removing the hoses and fittings to the block drains and going back to simple block drain plugs would be safer and easier in the long run than all the hassles it takes to disassemble the single point system each year.

Part of the problem is very likely the 1/4" NPT threaded holes in the blocks. Rust flakes seem to be larger than the 1/4" pipe fittings that are screwed into these holes.

I suppose if one were to drill/tap the holes to 3/8" NPT or maybe 1/2" NPT, the fittings would then be of sufficient inside diameter to pass various debris so as not to plug. But then the connected hoses and fittings would have to be the same or larger.

I am not sure you would want to drill holes that large in any block casting for fear of propagating a crack (I think my 454 ex manifolds do have 1/2" threaded holes). 3/8" might be ok. 1/2 might be a bit large for a block drain.

 

[Rick Stephens]

Part of the problem is very likely the 1/4" NPT threaded holes in the blocks. Rust flakes seem to be larger than the 1/4" pipe fittings that are screwed into these holes.

Can't argue with that Probably ever crossed anyone's mind when they designed it that it would get used in an open cooling system.

 

[Lou C]

I would do as some said and completely remove that foolish system that will eventually get you into trouble.
A cast iron engine used in marine use really should have at least a half closed cooling system . GM never intended raw water to used as a coolant for their cast iron engines.

 

[HT32BSX115]

A cast iron engine used in marine use really should have at least a half closed cooling system . GM never intended raw water to used as a coolant for their cast iron engines.

Dittos!!:thumb::thumb::thumb:

 

[05StingRay]

Ok so thus far I have kept the boat in my heated garage but I am getting to where I need the room in there for other things and need to store the boat in unheated spot at the lake. I am not super familiar with where the block drains are that you speak of clearing out in case of rust. Are you saying just pull all the hoses that connect to the engine block? If you have any pictures it would be great so I make sure I get the right things. Truly appreciate everyones help!
Nate

 

[Bt Doctur]

 

[05StingRay]

Does that hose run to the single point system?

 

[Bt Doctur]

The drain system has the 2 block drains and the 2 manifold elbow fitting drains that go to a sleeve #9

 

[BassinProf]

Okay, I just came upon this thread. Just to be clear, in the picture above to ensure the engine is drained I can trace the 4 hoses from the sleeve marked #9 to the block and manifolds, disconnect them from the engine and run a probe through the holes to make sure they aren't plugged. Is that right? Mine is a 5.0 MPI but I seem to remember it looking similar to the picture above.