'72 OMC 155/225ci engine Cooling system plugs popped out-why?

[hunt2labs]

2nd run of the year, after 5 minutes of idle speed then, 3/4 throttle for 5 min, then idle for 5, 3/4 throttle again both these popped off flooding my stern.
What might cause that and what do I need to do about it? Was this a blockage issue in the system? Perhaps I wasn't pumping any raw water? How to correctly replace them if it's that simple (I wish).

 

[Scott Danforth]

the core plugs only come out if the motor was not winterized properly and the block froze, cracking the block and pushing out the core plugs.

at a minimum, you need to install new brass core plugs, and pressure test your water jacket (see the stickies)

if it doesnt hold pressure your block is most likely cracked

if that is the case, your going to be looking for a Buick 225 odd-fire which may prove difficult as the motor has been out of production for over 44 years

 

[hunt2labs]

Scott, I appreciate the quick response even though that's not what I hoped to read.
I did drain the system and refill with RV antifreeze as I have in past years....hmmm
I looked at the stickies and could not find the pressure test for the water jacket.

If I cannot locate new brass core plugs (any ideas ?), or I notice an obvious crack in the block. I may be done with this "free"
boat/-that or I patch up the stern and repower with an outboard.
As always-thank you for all the help over the years!

 

[Scott Danforth]

go to your local NAPA or any other auto parts store that doesnt have to look in a book to get your core plugs


block off lines to manifolds, block off line from raw water pump, pressurize to 15psi. should hold air pressure forever.

FYI to vet your auto parts store. ask them for a valve cover gasket for a small block chevy. if they ask year, make and model, walk out. if they ask you center bolt or perimeter. then they know their butt from a hole in the ground and you can be confident to buy parts from them.

 

[hunt2labs]

Well, I must've forgotten to run the motor after draining the water this past winter. Replaced core plugs to find 2 fine cracks in upper block. No water in oil, so I ground down the areas and cracks, drilled pinholes at ends of cracks, wiped with acetone, and put on the JB Weld. Tested fine in yard on garden hose connection. Dropping in water for a real test with fingers crossed.
Thanks for the help.

 

[HT32BSX115]

Well, I must've forgotten to run the motor after draining the water this past winter. .

You probably just didn't get all the water drained out. When you remove the drain plugs, poking a wire or thin screwdriver in the holes clears the rust flakes from blocking the drains.....Sorry about that.

You really should pressure check the block with compressed air. Cast iron blocks are more likely to (freeze) crack internally than externally.....

You will probably find out though, look for oil bubbling out of the breather or milky oil if there's internal cracks.

Regards,

Rick

 

[hunt2labs]

So, after further testing, one of my "welds" seeped a bit so I roughed it up and slathered more compound on it.
That stuff is amazing! No leaks after WOT for several runs over 2 weeks!
Lesson learned.

 

[Redrig]

that is awesome , glad it turned out OK for you .

I didnt do the "wire in the drain" trick for the first couple of years when winterizing until I read so many horror stories on this site .

Good recovery !