Freeze-out plugs

Figment · Post by **Figment** » Tue Apr 22, 2008 8:20 am

I know it probably seems like a good idea to use the freeze-out plugs from NAPA. They're RIGHT down the street, and the things cost all of $0.55. Why pay ten times as much and wait three days to get bronze plugs?

Because.
Just because.

Post by **Tim** » Tue Apr 22, 2008 9:08 am

I sense a story brewing...

Tim Mertinooke · Post by **Tim Mertinooke** » Tue Apr 22, 2008 3:38 pm

Let me show my ignorance with a question. Would a freeze out plug be a plug that is tapped into the engine block where the coolant circulates? Is your engine raw water cooled or does it have a heat exchanger?

bcooke · Post by **bcooke** » Tue Apr 22, 2008 4:18 pm

...but spending money on boatstuff is FUN!

You should be thankful for the opportunity.

On the other hand, the rest of the engine is iron so is a bronze plug really necessary? Change the plug every spring and you should be fine. Or not. I really have no idea how long it will last. It would be a shame to have it blow out and cook your engine.

Of course then you could go diesel and spend more money which would be a very happy day indeed!

Rachel · Post by **Rachel** » Tue Apr 22, 2008 7:06 pm

Did someone leave Britton out in the rain? He seems a bit warped.

R.

(I can already hear you saying "It takes one to know one," by the way.)

Figment · Post by **Figment** » Wed Apr 23, 2008 7:42 am

Tim, yes a freeze-out plug is a sacrificial element intended to relieve the presure of frozen water in the block before it causes other costly damage. All engines have them as far as I know, raw or fresh. I'm raw.

The rest of the block is iron, but it's heavy iron, not a half-step above sheetmetal like the NAPA plugs. I suppose a freshwater cooled engine wouldn't have the corrosion problem with the NAPA plugs though, or at least not as quickly.

Change it out every spring? No, spank you.

Yes, of course I test-fired the engine with a hose and bucket a few days before launch. Nary an issue.
I'm guessing that exhaust backpressure was the straw that broke the camel's back. Firing the engine while still on the trailer, with the exhaust outlet quite submerged, created enough backpressure to overpressurize the cooling system and blow out the corroded plug.

Vrooom.
Hey what's all that water spraying around down there? I left the stuffing box loose, but not THAT loose.
It appears to be coming from the rear of the engine, probably a cracked hose between the pump and the jacket. Strange, it wasn't cracked the other day.
Eh, it doesn't appear to be more than the bilgepump can handle until I get to the dock.

no no, it's the freeze-out plug that's mounted behind the (now thoroughly soaked) ignition coil. Yeah. THAT's easily accesible.

I'm wondering if I should go through the gymnastics of replacing it in situ, or if I should pop the engine out onto the cabin sole. Eh, I'll toss a coin this weekend.

Tim Mertinooke · Post by **Tim Mertinooke** » Wed Apr 23, 2008 8:47 am

Thanks, I figured that's what they were.

bcooke · Post by **bcooke** » Wed Apr 23, 2008 9:52 am

I never actually looked to see where those plugs were.

Go expensive.

No, spank you.

Ouch!

catamount · Post by **catamount** » Wed Apr 23, 2008 11:43 am

Figment wrote:yes a freeze-out plug is a sacrificial element intended to relieve the presure of frozen water in the block before it causes other costly damage. All engines have them as far as I know, raw or fresh. I'm raw.

Huh? All engines? I'll have to look and see if mine has one! (Yanmar 2QM15G)

Tim A.

JSmith · Post by **JSmith** » Fri Apr 25, 2008 11:22 am

All engines have them. I think they should last pretty much for the life of the engine between major overhauls- ie till you buy the next engine.

Keeping a 50/50 mix of antifreeze and distilled water is as important to prevent freezing as it is to eliminate corrosion/ cavitation (pits liners) of the cooling water. There're additives in the antifreeze that slowly get used up which is why a flush and a refill of the system is important.

J Smith