Blew out freeze-out plug using blue air pump on 496 engine

[Danny Troy]

I was winterizing today and as usual, I used the blue air pump to first get the water out of the cooling system, before adding anti-freeze. I was shocked when I heard a pop and found water gushing out the bottom of the engine. The blown freeze-out plug is located on the starboard side. I was pressed for time so I couldn't locate the plug in the bilge. I wrapped some electrical tape around a bolt, until is was a tight fit and that at least allowed me to finish winterizing the engine. My question is, has this happened to anyone else? My boat lived it first 9 years in saltwater, so I'm thinking that plug was ready to go, and the air pressure was more than it could handle. Better it happened while on the trailer, than while underway. Also, when using the air pump, is water supposed to come out the bottom, more or less below where you air valve is? I did this for the last five years, and I'm pretty sure, but not positive, that water does enter the bilge when using the pump.

 

[paulswagelock]

You need to take a pic of where it blew out. The air lines go only to the raw water pump and the water distribution housing, not the block. It is impossible that pumping up those lines blew out a freeze plug in the block, they are not connected in any way. You could have blown apart the air actuator on the raw water pump which is the one on the starboard side. When you pump that system, water will drain to the bilge on both the starboard and port sides of the motor.

 

[Danny Troy]

Yes, I will have to get back to the boat and see exactly where the leak is. I'm pretty sure you are right, that it's not on the block. It also isn't on the raw water pump housing though. I'm familiar with that part, since I replaced it at least twice (not a fun job!). The blown plug was maybe 5/8" diameter, and was located aft of the raw water pump. I had to leave for work, so I couldn't mess with it, other than finishing adding antifreeze, so the marina could get to shrink-wrapping it.

You know, it just occurred to me that I didn't pull the pressure release ring before running antifreeze through the system. Is it possible that not releasing the air pressure would cause this, and that the leak is not really a leak, and just the starboard side drain? Grabbing at straws here!

 

[sfergson727]

Yes, I will have to get back to the boat and see exactly where the leak is. I'm pretty sure you are right, that it's not on the block. It also isn't on the raw water pump housing though. I'm familiar with that part, since I replaced it at least twice (not a fun job!). The blown plug was maybe 5/8" diameter, and was located aft of the raw water pump. I had to leave for work, so I couldn't mess with it, other than finishing adding antifreeze, so the marina could get to shrink-wrapping it.

You know, it just occurred to me that I didn't pull the pressure release ring before running antifreeze through the system. Is it possible that not releasing the air pressure would cause this, and that the leak is not really a leak, and just the starboard side drain? Grabbing at straws here!

I bet that is exactly what happened. Your boat is most likely fine. I’d pull all the drain plugs and leave them out until spring to be sure.

 

[Danny Troy]

Yes, I completely forgot how to use the air pump drainage system. If I didn't mess with the pump at all, all would have been fine. The good part is that I know the pink did flow through the system, as I saw it exiting out the outdrive.

 

[paulswagelock]

If you didn't release the pressure then yes it would continue to leak out. Should be fine though as the raw water pump is really high volume and those drains are small.

 

[Danny Troy]

I'll probably get in the boat before a hard freeze hits and re-do running the pink through, just to be safe (after releasing the pressure). Luckily I am able to store it at my home, so no problem with access.

 

[sfergson727]

I'll probably get in the boat before a hard freeze hits and re-do running the pink through, just to be safe (after releasing the pressure). Luckily I am able to store it at my home, so no problem with access.

No need to do that, just remove the plugs and keep them out for the winter. There is no benefit to keeping the antifreeze in the cooling system. The engines already have antifreeze in them from the closed cooling.

 

[Danny Troy]

I wonder how much of the water in the cooling system is ejected using the pump alone. Merc says it's not a substitute for winterizing, but in a pinch it's better than nothing. I use air pressure on my freshwater system to get the water out of the lines before running pink through (I'm anal that way!), although on my RV, for the last few years I only used air pressure to purge the system. I only add pink to the sink and shower traps. Haven't had a problem yet.

 

[sfergson727]

FWIW, I use the air drain system to initially remove the water, and then run antifreeze through it. I then drain it again with the air system, then manually remove the drain plugs. No additional fluid comes out upon removing the plugs, so the air drain system gets it all. I pull the plugs because old habits die hard, and after 35+ years of winterizing boats, it is just the way I roll. (plus I don't fully trust the air drain system)

 

[Danny Troy]

I haven't been pulling the plugs on this boat at all, thinking the pink is in there and will do it's job. To be on the safe side, I'll probably remove them when I add the door to the shrink-wrap, especially since I'm not 100% confident of the quality of my winterizing job this year!